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UNIT ONE
TOPIC ONE: LIFESTYLE, HEALTH AND RISK
WATER
- The chemical formula of water is H2O
- The atoms of water molecule are;
(i) 2 hydrogen atoms
(ii) 1 oxygen atom
- The structure of a water molecule is as follows:
- The positive and negative ( and !) indicate that there are small amounts of positive and
negative charge on the water molecule"
- The shape of water molecule is triangular"
- The #onds that $oin atoms of water are called coal!nt "on#$" % covalent #ond is formed when
electrons are shared #y atoms"
- &ater molecules are $oined #y %rog!n "on#$'One water molecule can #e $oined to ' other
water molecules #y hydrogen #onds as follows:
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Sta"ilit& o( a )at!r *ol!cul!
- &ater molecule is $ta"l!#ut its atoms are unsta#le"
- The outermost shell of hydrogen atom has 1 electron instead of 2 hence unsta#le" Oxygen
atom has electrons instead of * in its outermost shell hence unsta#le" To form a sta#le watermolecule the + atoms must share electrons and in the process covalent #onds are formed"
Di+ol! natur! o( )at!r
- &hen electrons are shared #etween atoms they are not shared e,ually #etween those atoms
#ecause some nuclei of these atoms attract more electrons than others" -n a water molecule
the nucleus of the oxygen attracts more electrons than the two nuclei of the hydrogen atoms"
.o oxygen is slightly negative while hydrogen atoms are slightly positive"
- T%! con#ition )%!r! in a *ol!cul! on! $i#! i$ $lig%tl& +o$iti! an# t%! ot%!r $i#! i$ $lig%tl&
n!gati! i$ call!# #i+ol! an# t%! *ol!cul! i$ call!# #i+olar, $o, a )at!r *ol!cul! i$ #i+olar'
I*+ortanc! o( )at!r a$ a #i+olar *ol!cul!'
1" .olvent for ionic and polar su#stances
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2" /edium for chemical reactions"
+" /edium for transport of su#stances"
Wat!r a$ a $ol!nt (or ionic an# +olar $u"$tanc!$
- -onic and polar su#stances have charges"
- 0xamples of polar su#stances are aminoaci#$ whose polar groups are H2(%mineamino group)
and 3OOH (car#oxyl group): and sugars whose polar group is OH"
- 0xample of an ionic su#stance is sodium chloride whose ions are aand 3l!"
- &hen ionic polar su#stance is placed in water the following ta4es place:
1" Attractionof the positive ions #y the oxygen of water and the attraction of the negative
ions #y the hydrogen atoms of water"
2" S!+arationof ions and polar groups+" Hration(surrounded #y water molecules) of these ions and polar groups i"e" dissolved"
Wat!r a$ a *!#iu* (or c%!*ical r!action$
- &hen in solid su#stances are not reactive"
- However when they dissolve in water and separate into ions and polar groups these ions and
polar groups (r!!l& *o!and hence they are c%!*icall& r!acti!'
Wat!r a$ a *!#iu* (or tran$+ort
- &ater transports ionic polar and non!polar su#stances"- &ater !a$il&transports ions and polar groups"
- However non!polar su#stances (no charges) such as lipids com#ine with proteins to form
li+o+rot!in$so that they are now transported #y water
- The transport systems in organisms include:
1" 3irculatory system 5 #lood
2" 6ymphatic system 5 lymph
+" 7ylem vessels in plants 5 water and minerals
'" 8hloem in plants 5 sucrose and amino acids"
I*+ortanc! o( %rog!n "on#$ in )at!r
- &hen in large num#ers hydrogen #onds are very hard to #rea4 using heat"
- &hen hydrogen #onds #etween water molecules are #ro4en water is converted into vapour
(individual water molecules)"
- Hrog!n "on#$ ar! (or*!# "!t)!!n t%! n!gati! c%arg! o( t%! o&g!n ato* -O&g!n
ato* %a$ . n!gati! c%arg!$/ an# t%! +o$iti! c%arg! o( t%! %rog!n ato*' &ater unli4e
3O2 is dipolar and therefore hydrogen #onds form #etween water molecules holding these
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molecules together forming li,uid" This is why at room temperature water is li,uid and 3O 2 is
gas"
PROPERTIES OF WATER DUE TO HYDRO0EN 1ONDS
2' Li3ui# at roo* t!*+!ratur!
- 9ue to its dipolar nature %rog!n "on#$are formed #etween water molecules hence; water
remains li,uid at room temperature"
.' Co%!$ion
- This is attraction force #etween similar molecules"
- Hrog!n "on#$hold H2O molecules together giving it cohesion"
- 3ohesion is important to transport water and dissolved su#stances in the xylem in a continuous
un#ro4en column"
4' A#%!$ion
- %ttraction force #etween non!identical molecules e"g" water and xylem wall"
- Hrog!n "on#$allow water to hold onto other su#stances e"g" to hold onto the walls of the
xylem to allow water to #e transported in a continuous un#ro4en column in the xylem"
5' Hig% $+!ci(ic %!at ca+acit&
- .pecific heat capacity (.H3) is the amount of energy re,uired to raise the temperature of 14g
of water #y 13"
- &ater has a high .H3 due to %rog!n "on#$(it is not easy to raise the temperature of water
to #rea4 strong hydrogen #onds)"
- .o the temperature of water remains relatively constant due to this property whose #iological
importance ++- include;
a) The temperature of water #odies such as oceans remains relatively
constant for the survival of a,uatic animals"
#) .ta#le temperature in living organisms so that enymes remain sta#le"
6' Lat!nt H!at o( a+oration
- 6atent heat of vaporiation is the amount of energy re,uired to convert li,uid to vapour"
- &ater has high latent heat of vaporiation due to %rog!n "on#$"
- The importance of this property of water is that water is a coolant (cooling agent) through
sweating in humans transpiration in plants panting in dogs and gaping in crocodiles"
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7 Hig% $ur(ac! t!n$ion
- .urface tension is the tig%tn!$$of water molecules on the surface forming a s4in li4e layer due
to %rog!n "on#$"
- The water molecules #eneath the ones on the surface pull the ones on the surface inwards #y
%rog!n "on#$ creating a s4in li4e layer"
- The #iological importance of high surface tension of water is to create a surface onto which
a,uatic insects such as pond s4aters canland move feed and #reed"
8' Uni3u! (r!!9ing #!n$it&
- The highest density of water is at '3 and not 3"
- %t '3 water is still li,uid #ut at 3 it #ecomes solid (ice) which floats due to low density"
- W%!n )at!r (r!!9!$, %rog!n "on#$ $tr!ngt%!nand this causes the water structure to
open up increasing the volume and decreasing the density i"e" water expands as it freees"
- The importance of this is that ice acts as a %!at in$ulator so that the lower atmospheric
temperature during winter does not affect the water #elow the ice hence the water #elow this
ice remains relatively warm for the survival of a,uatic animals"
Su**ar& o( t%! +ro+!rti!$ o( )at!r
1" 9ipolar nature of water ma4ing it;
(i) %n essential solvent for polar and ionic su#stances"
(ii) % transportation medium of su#stances"
(iii) % medium for chemical reactions"
2" Hydrogen #onds that ma4e water to have the following properties;
(i) high specific heat capacity
(ii) high latent heat of vaporiation
(iii)
(iv) cohesion
(v) adhesion
(vi) li,uid at room temperature
(vii) uni,ue freeing density
EDECEL ;USTIONS ON WATER
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CAR1OHYDRATES
- These are organic (car#on!containing) su#stances made up of + elements:
i) 3ar#on
ii) Hydrogen
iii) Oxygen
- The 2 ma$or groups of car#ohydrates are:
a) .ugars 5 monosaccharides = disaccharides"
#) on!sugars 5 polysaccharides"
a/ Sugar$
! These are sweet tasting"
! They are divided into 2:
(i) monosaccharides
(ii) disaccharides
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% car#onyl group #ecomes an aldehyde group when a hydrogen atom is attached to it" -t
is this aldehyde group that reduces metallic ions" % monosaccharide with an aldehyde
group is called aldose sugar e"g" glucose and galactose"
#) Aetone group
% 4etone group is formed when the car#onyl group is #etween car#on atoms" -t reduces
metallic ions #ut when it is converted first to aldehyde group" /onosaccharides with
4eto!groups are called 4etose sugars e" g fructose"
ote: so monosaccharides are either;
a) %ldoses 5 glucose
#) Aetoses 5 fructose
Lin!ar an# ring (or*$ o( *ono$acc%ari#!$
- 6inear forms are less sta#le #ut they r!#uc! *!tallic ion$#ecause of availa#ility of car#onyl
groups"
- Bing forms have *ol!cular $ta"ilitut cannot reduce metallic ions due to loss of car#onyl
groups so in CenedictDs test heating the monosaccharide is meant to open up the ring form
into the linear form to expose the car#onyl groups that reduce the metallic ions"
Trio$!$
- They are the simplest monosaccharides"
- They are intermediates during photosynthesis and respiration"
- 0xample is glyceraldehyde
P!nto$!$
- They are monosaccharides"
- They are E car#on sugars"- There are 2 main types of pentoses;
a) Bi#ose (3EH1OE)
#) 9eoxyri#ose (3EH1O')
- The difference #etween ri#ose and deoxyri#ose is that on car#on atom 2 ri#ose has OH group
and deoxyri#ose has $ust H group"
- The importance of pentoses include:
a) .ynthesis of nucleic acids (9% and B%)" 9% consists of deoxyri#ose while B%
consists of ri#ose
#) .ynthesis of a nucleotide co!enymes (hydrogen acceptors) such as %9 and F%9
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c) .ynthesis of energy carrier molecules such as %T8 %98 and %/8"
H!o$!$
- These are monosaccharides"
- They are car#on sugars"
- They consist of #oth linear and ring forms"
- Their chemical formula is 3H12O"- They are all respiratory su#strates i"e" they are #ro4en down to provide energy during
respiration"
- The common hexoses are glucose fructose and galactose
0luco$!
- There are 2 isomers of glucose
a) ! glucose
#) ! glucose
! glucose ! glucose
Not!
- -n ! glucose OH on car#on atom One (31) is #elow the ring or #elow car#on atom one (31)"
- -n ! glucose the OH on car#on atom one (31) is a#ove the ring or a#ove car#on atom one (31)"
- The importance of i$o*!ri$*in glucose is that it gives different types of polysaccharides as
follows:
a) .tarch and glycogen are made up of glucose
#) 3ellulose is made up of ! glucose
- The importance of glucose include;
a) -t is a respiratory su#strate that provides energy when respired"
#) -t synthesies disaccharides and polysaccharides"
Fructo$!
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- Fructose is a sugar which is present naturally in fruits some vegeta#les and honey" The
structure of fructose is as follows:
- The importance of fructose include;
a) -t is a respiratory su#strate that is respired to provide energy"
#) -t synthesies disaccharides 5 sucrose"
c) -t sweetens the fruits which attract animals facilitating seed dispersal"
0alacto$!
- -t occurs in our diet mainly as part of the disaccharide sugar called lactose (mil4 sugar)
- The importance of galactose include;
(i) Food for infants as a respiratory su#strate"
(ii) .ynthesis of disaccharide called lactose (glucose galactose)
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DISACCHARIDES
- The formula for disaccharide is 3nH2n!2On!1 where n is 12
- They are sugars made up of 2 monosaccharides"
- They are also called dou#le sugars"
- The common disaccharides are;(i) /altose (malt sugar) >lucose >lucose
(ii) .ucrose (cane sugar) glucose fructose
(iii) 6actose (mil4 sugar) >lucose galactose
- The chemical formula for all disaccharides is 312H22O11
Con#!n$ation r!action in t%! (or*ation o( #i$acc%ari#!$
- 3ondensation reaction involves a lo$$ o( )at!r *ol!cul!when 2 monosaccharides $oin through a
#ond"
- -n disaccharides the #ond that $oins the monosaccharides together is called a gl&co$i#ic "on#'
Hrol&$i$ r!action$ in "r!a=ing #o)n #i$acc%ari#!$'
- Hydrolysis reaction involves the a##ition or gain o( a )at!r *ol!cul! to #rea4 down the
glycosidic #ond in the disaccharide in order to get individual monosaccharides"
- There are 2 types of hydrolysis;
2' Aci# %rol&$i$
- The disaccharide is #oiled with dilute acid to #rea4 down the glycosidic #ond"
.' En9&*atic %rol&$i$
- The disaccharide is incu#ated with the enyme to #rea4 the glycosidic #ond as shown #elow;
/altose maltase glucose glucose
.ucrose sucrase glucose fructose6actose lactase glucose galactose
The following diagram shows the hydrolysis and condensation of maltose;
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- 1! glycosidic #onds cause #ranching
- OH on car#on atom 2 attracts one another #y H!#onds causing coilinghelical shape
- 3oiling and #ranching ma4es the molecule compact so that many of them can #e stored in small
spaces (cell)"
The following ta#le gives differences #etween amylose and amylopectin
%mylose %mylopectin
.hort (+ glucose molecules) 6ong (1E glucose molecules)
In#ranched hence only 1' glycosidic
#onds
Cranched hence has 1' and 1
glycosidic #onds
+G starch G starch
Turns #lue #lac4 with iodine solution Turns reddish #rown with iodine solution6ess compact hence less amount of
energy
/ore compact hence more energy
T%!$! ar! t%! $i*ilariti!$ "!t)!!n a*&lo$! an# a*&lo+!ctin>
1" Coth are polysaccharides
2" /ade of ! glucose molecules
+" >lycosidic #onds $oin the glucose molecules"
'" Coth are 3oiledhelical
E" 0nergy storage molecules in plant cells
0l&cog!n
- -t is a polysaccharide
- /ade up of ! glucose molecules
- >lucose are $oined together #y glycosidic #onds
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+" &axes
Trigl&c!ri#!$
- They are natural fats and oils"
- %t room temperature fats are solids and oils are li,uids"
- Triglycerides are lipids made up of ;
(i) T%r!!Fatty acids"
(ii) On!glycerol molecule"
- These + fatty acids and glycerol are $oined #y !$t!r "on#$
- 0ach ester #ond is formed in a condensation reactionesterification reaction in which a water molecule is
lost" The reaction is catalyed #y an enyme"
0l&c!rol
! The structure of glycerol is as follows;
! The chemical formula for a glycerol molecule is 3+H*O+"
! There is only 1 type of glycerol molecule i"e" all glycerol molecules are the same"
Fatt& aci#$
- Triglycerides consist of + fatty acids"
- There are different types of fatty acids which vary in the followings ways;1" The length of the hydrocar#on chain from *!2: car#ons"
2" The a#sence or presence of car#on 5car#on dou#le #onds"
+" The num#er of dou#le car#on!car#on #onds"
'" The mix of fatty acids i"e" all the + are the same or all the + are different or any other
com#inations"
- % fatty acid is made up of 2 components;
1" 3ar#oxylic group (3OOH)
2" Hydrocar#on 3hain (3H2)n3H+"
- % fatty acid can #e represented as follows
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For*ation o( trigl&c!ri#!
- Fatty acids $oin the glycerol molecule one at a time #y an !$t!r "on#i"e" monoglyceride diglyceride and
triglyceride
- Formation of an ester #ond is through condensation reaction where a water molecule is formed" To form
water glycerol loses hydrogen and fatty acids losses OH"
T&+!$ o( (att& aci#$
a) .aturate fatty acids#) Insaturated fatty acids
Saturat!# (att& aci#$
- They have the maximum num#er of hydrogen atoms and have only single car#on 5car#on #onds in their
%rocar"on c%ain"
- .aturation refers to the amount of hydrogen in the molecule"
- Triglycerides with saturated fatty acids are called saturated triglycerides"
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- 9ue to lac4 of dou#le car#on 5 car#on #onds in the hydrocar#on chain there is no straining hence no
4in4ing (#ending) and therefore they have high melting point a#ove '3 and therefore they remain solid
at #oth room and #ody temperatures"
- .aturated fatty acids have dou#le #ond #etween car#on and oxygen in the car#oxylic group"
- The following ta#le summaries examples of saturated fatty acids and the saturated triglycerides they
are found in"
Fatt&
aci#$
No o( #ou"l! C@C
"on#$
A"un#ant in -$aturat!# trigl&c!ri#!$/
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.aturated Insaturated
1" /aximum num#er of hydrogen atoms 6ow num#er of hydrogen atoms
2" Have only single 3!3 covalent #onds
in the hydrocar#on tail
Have dou#le covalent #onds (3@3) in the
hydrocar#on tail
+" Have no 4in4s due to lac4 of dou#le
covalent #onds hence has a straight
chain
Have 4in4s due to presence of dou#le
covalent #onds hence has a #ent chain
'" .olid at room temperature due to
high melting points
6i,uids at room temperature due to low
melting points
Function$ o( trigl&c!ri#!$
2' En!rg& $tor!
- >enerates more than twice the energy generated #y car#ohydrates" Triglycerides are essential energy
stores #ecause of the following properties;
a) -nsolu#le (no osmotic effect)
#) >enerates a lot of energy due to long car"on c%ain$"
c) 3ompact hence a lot can #e stored in the cell"
.' 1uo&anc& in a3uatic ani*al$
- Cuoyancy is the a#ility to float
- Triglycerides are less dense than water hence a,uatic animals are a#le to float e"g" #lu##er in whales
which contains oil"
4' H!att%!r*al in$ulation
- Triglycerides are poor thermal conductors (poor conductors of heat) e"g" adipose tissue (tissue that
stores a lot of fat #eneath the s4in) reduces heat loss from the #ody"
5' Prot!ction o( #!licat! organ$
- Triglycerides are soft and therefore cushion the delicate organs such as heart lungs and 4idneys so that
they are not damaged"
6' Sourc!$ o( *!ta"olic )at!r )%!n oi#i9!#
- /eta#olic water is important in desert mammals such as camels to supplement the little water they get"
P%o$+%oli+i#$
- % phospholipids is a molecule made up of:
a) 1 glycerol
#) 2 fatty acids
c) 8hosphate group
d) 0ster #onds $oin fatty acids to glycerol
e) 8hospho!ester #ond $oins phosphate to glycerol"
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1" >lycerol
2" Fatty acids
+" 8hosphate group
- The summaried structure of phospholipids
1! 8hosphate heads
2! Fatty acids tail
- 8hospholipids are used to synthesie #iological mem#ranes"
C%ol!$t!rol
- This is a lipid"
- 3holesterol is not a saturated fat #ut is made up in the liver from saturated fats a#sor#ed from food"- The structure of cholesterol is
- -n the cell mem#ranes cholesterol has 2 ma$or roles;
1" 3ontrol fluidity so that the cell mem#rane is not too fluid or too rigid2" 8rovides the mechanical strength to the cell mem#ranes" .o the cell mem#ranes with little or no
cholesterol easily #rea4 down"
EDECEL ;USTIONS ON LIPIDS
1"
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Tran$+ort $&$t!* in %u*an$
- The 2 transport systems in humans are:!2' Car#ioa$cular $&$t!*
.' L&*+%atic $&$t!*
- Humans do not rely on diffusion for the transport of su#stances in their #odies and therefore
they need a specialied transport system i"e" cardiovascular and lymphatic system" This is
#ecause humans have a small surface area to volume ratio and therefore cannot rely on
diffusion for transport of su#stances"
- -n summary car#ioa$cular an# l&*+%atic $&$t!* ar! inol!# in *a$$ tran$+ort o(
$u"$tanc!$ to o!rco*! t%! li*itation o( #i((u$ion in *!!ting t%! r!3uir!*!nt$ o( t%!
organi$*$'
- .mall organisms such as amoe#a have large surface area to volume ratio and therefore they
rely on diffusion for a#sorption and movement of su#stances"
- The following cu#es illustrate the concept of surface area (.%) to volume ratio
."%: Jolume ."%: Jolume
(2 x 2) : 2 x 2 x 2 (* x *) : * x * x *
2':* +*':E12
.%J@2'*@4 .%J@+*'E12@B'86
Car#ioa$cular $&$t!* 22
- This is the mass transport system in humans"
- -t consists of the heat (cardio) and the #lood vessels (vascular)"- 3irculation is the passage of #lood through the #lood vessels"
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- The features of the mass transport system such as cardiovascular system include;
(i) % system of vessels that carries su#stances"
(ii) % way of ma4ing sure that su#stances are moved in the right (one) direction"
(iii) % means of moving materials fast enough to supply the needs of organism e"g" pumping of
the heart and the use of active transport"
(iv) % suita#le transport medium e"g" #lood lymph
Function$ o( t%! car#ioa$cular $&$t!*
1" -t transports the re,uirements needed #y the cells of the #ody e"g" glucose and oxygen"
2" -t transports the waste products of meta#olism from the cells e"g" urea and 3O2"
+" -t carries hormones from endocrine glands to target cells"
'" -t forms part of the defense system of the #ody"
E" -t distri#utes heat throughout the #ody hence maintains homeostasis"
T%! %u*an %!art
T%! $tructur! o( t%! %u*an %!art
- -t is a muscular pumping organ"
- -t is a dou#le pump (right and left)"
- -t is made up of cardiac muscles (heart muscles)"
- -t has ' cham#ers i"e" 2 atria and 2 ventricles"
- -t is associated with the #lood vessels and valves"
T%! %!art a$ a #ou"l! +u*+
- The human heart is a dou#le pump"
- These 2 pumps are $oined together and wor4 in perfect synchrony"
- The right and the left pumps of the heart are separated #y a septum"
- The right side of the heart (right pump) receives deoxygenated #lood from the #ody via the
vena cava and it pumps it to the lungs for oxygenation and removal of 3O 2 through the
pulmonary artery"- The left side of the heart (left pump) receives oxygenated #lood from the lungs through
pulmonary vein and pumps it to the #ody via the aorta"
- The #lood in the left side of the heart does not mix with the #lood in the right side of the
heart"
T%! car#iac *u$cl!
- -t is also called the muscle of the heart"
- -t has a special property i"e" it contracts rhythmically without resting or fatigue"
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- %tria have thinner cardiac muscles while ventricles have thic4er cardiac muscles" However the
left ventricle has thic4er muscles than the right ventricle"
T%ic=n!$$ o( car#iac *u$cl!
- The thic4ness of the cardiac muscles determines the distance through which #lood is pumped"
The thic4er the muscle the more the contraction the greater the pressure and the longer the
distance and vice versa as discussed #elow;
a/ T%in car#iac *u$cl!$ o( t%! atria
They pump #lood to the shortest distance when they contract i"e" from the atria
to the ventricles via atrio!ventricular valves (%J valves) i"e" tricuspid and #icuspid
(mitral) values"
%s the #lood enters the atrium via vena cava and pulmonary vein due to its
weight the %"J valves open and allow two!third of the ventricles to #e filled
passively with #lood so that the contraction of the atria tops up the #lood in the
ventricles"
"/ T%ic= *u$cl!$ o( t%! rig%t !ntricl!
&hen it contracts it pumps #lood to the lungs via pulmonary artery and #ac4 to
the left atrium via pulmonary vein" This circulation of #lood from the heart to the
lungs and #ac4 to the heart is called +ul*onar& circulation"
c/ T%ic=!r *u$cl!$ o( t%! l!(t !ntricl!
These muscles contract powerfully to generate more pressure that pumps #lood
from the left ventricle to the #ody via the aorta and #ac4 to the right atrium via
the vena cava" This circulation of #lood from the heart to the #ody and #ac4 to
the heart is called $&$t!*ic circulation"
Function$ o( t%ic=!r car#iac *u$cl!$ o( t%! l!(t !ntricl!>
1" To pump #lood to all parts of the #ody"
2" To overcome the effect of elastic recoil"
+" To overcome the com#ined resistance of multiple capillary networ4s"
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Dou"l! circulation in %u*an$
- This means that the #lood flows through the heart twice in one circulation"
- -t involves pulmonary circulation (circulation of #lood from the heart to the lungs and #ac4 to
the heart) and systemic circulation (circulation of #lood from the heart to the #oy and #ac4 to
the heart)"
N1
Fish have single circulation where #lood flows from the #ody to the heart then from the heart to
the gills and from the gills it does not flow to the heart #ut it flows to the #ody" .o it flows to
the heart once in a single circulation"
A#antag!$ o( #ou"l! circulation in %u*an$>
1" %llows differential pressure #etween the lungs and the rest of the #ody so that the lungs
have low pressure of #lood and the #ody has high pressure:
6ow pressure in the lungs ensures that there is enough time for the #lood to
a#sor# O2 =remove 3O2prevents the capillaries from #ursting and to prevent
ultra filtration"
High pressure in the #ody ensures that the #lood reaches all parts of the #ody itovercomes the effects of elastic recoil and the effects of the com#ined
resistance of multiple capillary networ4s"
2" Bepressuriation of #lood due to further pumping #y the heart so that the re,uirements
can #e moved to the #ody faster and the wastes can #e moved to the lungs faster"
+" o mixture of oxygenated and deoxygenated #lood" Oxygenated #lood is in the left side and
deoxygenated in the right side"
'" /uscles of mammals need a lot of oxygen and dou#le circulation serves this purpose"
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1loo# !$$!l$ a$$ociat!# )it% t%! %!art
1" -nferior vena cava 5 it carries deoxygenated #lood from the lower part of the #ody to the
right atrium"
2" .uperior vena cava 5 it carries deoxygenated #lood from the head nec4 arms and chest to
the right atrium"
N1: !na caa i$ t%! larg!$t !in
+" 8ulmonary artery 5 together with um#ilical cord arteries they are the only arteries that
carry deoxygenated #lood" -t carries deoxygenated #lood from the right ventricle to the
lungs for the removal of 3O2 and a#sorption of O2" At t%! "a$! o( t%! +ul*onar& art!r&
there is a valve called pulmonary (right) semi!lunar valve whose role is to prevent the #ac4
flow of #lood from the pulmonary artery #ac4 into the right ventricle"
'" 8ulmonary vein 5 together with um#ilical cord vein they are the only veins that carry
oxygenated #lood" -t carries oxygenated #lood from the lungs to the left atrium"
E" %orta 5 this is the largest artery" -t carries oxygenated #lood from the left ventricle to
the #ody in order to deliver re,uirements such as oxygen to the tissues" At t%! "a$! o(
aorta there is a valve called aortic (left) semi!lunar valve that prevents the #ac4flow of
#lood from the aorta #ac4 into the left ventricle"
" 3oronary arteries! These are right and left coronary arteries that supply the heart muscles
with re,uirements" They are the first arteries to #ranch from the aorta"
ALES ASSOCIATED WITH THE HEART
They are atrio!venticular valves found #etween the atria and the ventricles" These are;
2/ 1icu$+i# al! -or *itral al!/
- it is found #etween the left atrium and the left ventricle"
- its functions are:
a) allows #lood to flow from the left atrium into the left ventricle"
#) 8revents the #ac4flow of #lood from the left ventricle to the left atrium
during ventricular systole so that the #lood enters the aorta"
./ Tricu$+i# al!
- -t is found #etween the right atrium and the right ventricle"
- -ts functions are;
a) -t allows #lood to flow from the right atrium into the right ventricle"
#) -t prevents the #ac4flow of #lood from the right ventricle in the right atrium
so that the #lood enters the pulmonary artery"
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The external and internal structures of the human heart
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.ummary of the #lood flow through the heart;
1" Jena cava
2" Bight atrium
+" Tricuspid valve
'" Heartstrings (tendons)
E" 8apillary muscles" Bight ventricle
" Bightpulmonary semi!lunar valve
*" 8ulmonary artery
?" 6ungs
1" 8ulmonary vein
11" 6eft atrium
12" Cicuspid valve
1+" 6eft ventricle
1'" 6eftaortic semi!lunar valve
1E" %orta1" Cody
1" .eptum
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- The rate of the heart #eat shows how fast the heart is contracting"
Factor$ t%at a((!ct t%! %!art rat!
- Heart rate is the num#er of heart per minute"
- %n average adult has a heart rate of a#out #eats per minute"
- The following factors affect the heart rate
(i) 8hysical exercise 5 during exercise tissue need more O2and glucose and so the heart
must #eat faster to supply them with these re,uirements and to remove the waste"
(ii) 8ermissi#le drugs 5 these include caffeine and nicotine that raise the heart rate "
(iii) -llegal drugs 5 they raise the heart rate"(iv) .tress and excitement 5 they raise the heart rate due to the production of adrenaline"
(v) Best and relaxation 5 they lower the heart rate"
(vi) %ge 5 in small children it is much higher than adults"
(vii) Temperature ! the higher the temperature the higher the heart rate"
Car#iac c&cl!
- -t is the se,uence of events that ta4e place in one heart #eat and it last for "*+ second" -t is
initiated at the sino!atrial node (.%) also called pacema4er" These events are: %trial systole
("1s) ventricular systole ("+s) and complete cardiac diastole ("'s)"
E!nt$ o( t%! car#iac c&cl!
2' Atrial $&$tol!
- This is the contraction of the atria when they are filled up with #lood"
- -ts role is to pump #lood into the ventricles from the atria via %J valves"
- -t lasts for a#out "1s"- 9uring atrial systole %J valves are opened"
- 9uring atrial systole semi!lunar valves are closed"
- 9uring atrial systole atria are contracted and ventricles are relaxed"
2" Jentricular systole
- This is the contraction of the ventricles when they are filled up with #lood"
- -ts role is to pump #lood into the aorta and the pulmonary artery from the ventricles"
- -t lasts for "+s
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- 9uring ventricular systole the %J valves close to prevent the #ac4flow of #lood from the
ventricles into the atria and to #uild up pressure in the ventricles"
- 9uring ventricular systole semi!lunar valves are forced to open"
- 9uring ventricular systole atria are relaxed and ventricles are contracted"
+" 9iastole (3omplete cardiac diastole)
- This is the relaxation of the heart after ventricular systole"
- 9uring diastole the whole heart is relaxing reducing pressure in the heartso that #lood flows
into the atria via the vena cava and pulmonary vein hence refilling the heart with #lood"
- .o the role of the diastole is to refill the heart with #lood"
- -t lasts for "' second"
- 9uring diastole the %J valves open"
- 9uring diastole the semi!lunar valves are closed"
Pr!$$ur! c%ang!$ in t%! l!(t +art o( t%! %!art #uring car#iac c&cl!'
- 9uring the left atrial systole the atrial pressure is greater than the left ventricular pressure
#ecause of the refilling of the left atrium #y the #lood from the pulmonary vein"
- The #lood enters the left ventricle"
- &hen the pressure of the left ventricle exceeds the pressure of the left atrium the #icuspid
valve closes to prevent the #ac4flow of #lood from the left ventricle into the left atrium"- The pressure of the left ventricle rises suddenly and forces open the left semi!lunar valve
- The pressure in the aorta #egins to rise #ut still it is less than the pressure in the left
ventricle"
- &hen the pressure in the aorta exceeds the pressure in the left ventricle the left semi!lunar
valve closes to prevent the #ac4flow of #lood to the left ventricle from the aorta"
- This causes the pressure in the left ventricle to suddenly drop causing relaxation of the heart
(diastole) and during this time there is refilling of the atria that causes the opening of the %J
valves"- The pressure in the aorta continues to reduce as the #lood flows towards the tissues"
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c! Cicuspid valve closes
d! %ortic pressure
e! %ortic semi!lunar valve opens
f 5 %ortic semi!lunar valve closes
g 5 Cicuspid valve opens
a) 3alculate the heart rate from this graph;
N'1'
I#!nti(& t)o r!+!ating +oint$ an# calculat! t%! #i((!r!nc! to g!t t%! ti*! (or I %!art
"!at'
1 #eat @ " second
x 5 seconds
x @ 1 #eats minute
#) 9uring cardiac cycle the pressure in the right ventricle rises to a maximum of a#out +"+
48a as opposed to 1E 48a in the left ventricle" 9escri#e and explain this difference"
6eft ventricle has thic4er muscles than right ventricle and so contract more
powerfully to generate more pressure unli4e the right ventricle"
The pressure in the left ventricle is to pump #lood to all parts of the #ody to
overcome the effects of elastic recoil and to overcome the com#ined resistance of
multiple capillary networ4s" The low pressure in the right ventricle is to ensure there
is enough time for the #lood to a#sor# O2and to remove 3O2to prevent the #ursting
of lung capillaries and prevent ultra filtration"
c) -mmediately after the ventricular systole which ventricle has higher pressureK %nd whyK
Bight ventricle;
This is #ecause it has relatively thinner muscles than the left ventricle and
therefore does not pump out all the #lood leading to relatively more pressure"
Pr!$$ur! c%ang!$ in t%! "loo# !$$!l$
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2' Pr!$$ur! in t%! art!ri!$
The pressure of #lood in the arteries varies with the heart #eat i"e" when the heart contracts the
#lood pressure increases and when the heart relaxes and refills the #lood pressure in the arteries
decreases" -n the arteries there is a high pressure #ecause of the following reasons"
a) 6ittle peripheral resistance due to relatively wider lumen"
8eripheral resistance is the friction #etween the #lood and the inner smooth surface of the
#lood
vessels and its role is to slow down the flow of #lood"
#) The pulsing of the heart is high"
.' Pr!$$ur! in t%! art!riol!$
The pressure gradually decreases due to:a) -ncreased peripheral resistance due to narrower #lood vessels"
#) The artery divides into more arterioles reducing the pressure"
4' Pr!$$ur! in t%! ca+illari!$
8ressure decreases due to;
a) -ncreased peripheral resistance due to very narrow #lood vessels"
#) Beduced pulsing of the heart as these capillaries are far away from the heart"
c) 6oss of su#stances into the tissues due to ultra!filtration"
d) Formation of many capillaries (capillary networ4) that reduces the pressure"
;u!$tion$
1" 9escri#e why the #lood pressure in the capillaries does not increase even though they are very narrowK
This is #ecause they form many capillaries which together havegr!at!r total cro$$ $!ction ar!a
than that of the main artery and so the+r!$$ur! i$ $%ar!##y these many capillaries hence reducing
the pressure"
2" &hat is the importance of low #lood pressure in the capillariesK
-t gives enough time for the exchange of materials through diffusion with the tissues"
To prevent #ursting of capillaries
+" &hat are the adaptations of capillaries to exchange of su#stancesK
The wall is one cell thic4 to reduce diffusion distance They have pores to allow for the exchange of su#stances
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They form capillary networ4 to increase the .% of exchange"
o collagen fi#ers smooth muscles and elastic fi#res
'" &hat controls the pressure of #lood in the arteriesK
a) 3ontraction and relaxation of the heart" 3ontraction increases pressure in the arteries and
relaxation decreases pressure"
#) %therosclerosis" -t can permanently change the arteries #y narrowing them and cause permanent
rise in pressure which can lead to cardiovascular diseases"
c) Throm#osisE" &hat is the disadvantage of elastic recoil in the arteryK %nd how does the heart overcomes this"
0lastic recoil is the shrin4ing of the artery when elastic fi#res slac4enloosen due to the relaxation
of the heart" This can lead to the #ac4flow of #lood" However due to powerful contraction of the
large muscular left ventricle more pressure is generated which overcomes elastic recoil"
" Criefly descri#e #lood pressure measurements
- Clood pressure is measured in millimeters of mercury (mmHg)
- Clood pressure is measured using an apparatus called sphygmomanometer
- .ystolic reading of a 12mmHg and a diastolic reading of *mmHg i"e" 12* is regarded as normal
- .ystolic #lood pressure is when the ventricles contract powerfully while diastolic #lood pressure is when
the ventricles relax"
- % sustained value of over 1'? is called hypertension" This damages arteries"
- % sustained value of ? or low is called hypotension" % wea4ened heart will produce hypotension"
C
- The systolic pressure is the maximum pressure when the heartventricles contracts;12:mmHg
- The diastolic pressure is the minimum pressure when the heart relaxes; *:mmHg
- The two are measured using sphygmomanometer"
1LOOD ESSELS
/ammals such as humans have closed circulatory system" This means that #lood flows in
vessels" These vessels are;
1" %rteries
2" Jeins
+" 3apillaries
.ome organisms such as insects have open circulatory system" The heart of the insect is a
long tu#e" -t pumps #lood into the #ody cavity so that #lood surrounds the cells" The #lood
then passes #ac4 into the heart from the #ody cavity" The insect does not need #lood
vessels to transport #lood around the #ody #ecause;
1" -nsects have large surface area to volume ratio and so #i((u$ionof #lood is enough to
exchange materials"
2" The cells are in contact with the #lood"
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+" The heart and #lood are close together hence movement of #lood #ac4 to the heart is fast
'" 6ow meta#olism (chemical reactions in a cell) in insects and therefore only need diffusion of
#lood to get the re,uirements"
T%! "loo# !$$!l$, $tructur!$ an# t%!ir (unctional $igni(icanc!
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&hen the
a#ove leg
muscle contracts valve < closes to +r!!nt "ac= (lo)of #lood in the vein" Jalve 4 opens due to
increased pressure of #lood"
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!$$!l Structur! Functional $igni(icanc!
1" %rtery Tunica adventitia 5 collagen fi#res
= some elastic fi#res"
3ollagen fi#res provide strength so
that arteries )it%$tan# %ig%
+r!$$ur!of #lood without #ursting"
-n addition they prevent
overstretching of arteries"
Tunica media
a) .mooth muscles
#) 0lastic fi#res
c) .ome collagen fi#res
They contractand r!lato alter
the diameter of lumen to r!gulat!
"loo# (lo)'
They $tr!tc%and r!coilthe
arteries to *aintain +r!$$ur! o(
"loo#or smoothen #lood flow"
For strength
Tunica intima (endothelium) 5
smooth single layer of cells
(s,uamous epithelium)"
-t reduces friction #etween the
walls and the #lood to !a$! "loo#
(lo)
arrow lumen To *aintain %ig% +r!$$ur! o(
"loo#'
2" Jein Tunica adventitia 5 thinner
collagen fi#res
Clood is under low pressure hence
vessels cannot #urst"
Tunica media
a) Jery little smooth muscle
#) Jery little elastic fi#res
o pulse of #lood so no alteration
of the diameter of the lumen
o pulse of #lood hence no
stretching and recoiling of veins
Tunica intima 5 (endothelium) 5
smooth single layer of cells!
s,uamous epithelium"
Beduces friction #etween the wall
and #lood to !a$! "loo# (lo)
&ide lumen -t acts as a "loo# r!$!roirto
accommodate large volume of #lood
due to low #lood pressure
Jalves To stop the #ac4 flow of #lood as it
is under low pressure
+" 3apillaries Jery thin wall (1 cell thic4) %llows rapid exchange of su#stances
#etween #lood and tissues i"e" reduces
diffusion distance
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8ores %llows exchange of su#stances
3apillary networ4#ed -ncreases surface area of exchange of
su#stances
o valves arrow lumen
o collagen fi#res
o smooth muscles and
o elastic fi#res
.o that they can !a$il& (it
"!t)!!n c!ll$
Structural #i((!r!nc!$ "!t)!!n !in$ an# ca+illari!$
!in$ Ca+illari!$
1" + layers
2" Jalves
+" o pores
'" &ider lumen
E" Have collagen fi#res elastic
fi#res and smooth muscles
1 layer
o valves
8ores
arrower lumen
one
Structural #i((!r!nc!$ "!t)!!n art!ri!$ an# ca+illari!$
!in$ Ca+illari!$
1" + layers
2" o pores
+" 3ollagen fi#res elastic fi#re and
smooth muscles
1 layer
8ores
one
Structural #i((!r!nc!$ "!t)!!n art!ri!$ an# !in$
Art!ri!$ !in$
1" Thic4 walls
2" .mall lumen
+" o series of valves
'" 9eeply seated
Thin walls
&ide lumen
Have series of valves
.hallowly seated
Functional #i((!r!nc!$ "!t)!!n art!ri!$ an# !in$
Art!ri!$ !in$
1" 3arry #lood away from the heart 3arry #lood to the heart
2" 0xcept for pulmonary artery and
um#ilical cord artery they carry
0xcept for pulmonary vein and um#ilical
cord vein they carry deoxygenated
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oxygenated #lood #lood
+" They carry #lood under high
pressure
They carry #lood under low pressure
'" Clood flows in pulses Clood flows smoothly"
D!$cri"! %o) t%! "loo# *o!$ in !in$ (ro* t%! "o#& "ac= to t%! %!art
1" .eries of semi!lunar valves that prevent #ac4 flow of #lood"
2" 3ontraction of s4eletal muscles so that they push on veins for #lood to move forward"
+" Creathing in (inhalationinspiration)! this reduces pressure in the thoracic cavity forcing
the #lood to move towards it"
'" 9iastole! this cause reduced pressure in the heart and the #lood moves towards it"
;u!$tion$ on Tran$+ort
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PLATELETS AND THE 1LOOD CLOTTIN0 PROCESS
Plat!l!t$
- 8latelets are also called throm#ocytes"
- They are tin& (rag*!nt$ of large cells called *!ga=ar&oc&t!$which are found in the #one
marrow"
- There are a#out 1E to ' platelets per 1mm+of #lood"
- The role of platelets is "loo# clotting +roc!$$"
- Their life span is E to ? days"
- 8latelets have no nucleus #ut they contain a clotting factor (enyme) called t%ro*"o+la$tin"
1LOOD CLOTTIN0
There are 2 types of #lood clots;
1" 6ife saving clot ! in the s4in
2" 6ife threatening clot 5 in the #lood vessel
1loo# clotting in t%! $=in -li(! $aing clot/
This is a vital defense mechanism for the #ody #ecause when one suffers a cut or grae
the role of clotting is to;
(i) /inimie #lood loss
(ii) 8revent entry of pathogens
(iii) 8rovide a framewor4 for repair"
Proc!$$ o( "loo# clotting in t%! "loo# !$$!l -Li(! t%r!at!ning clot/
- This is a ca$ca#! o( !!nt$leading to #lood clotting"
- Clood clotting process is stimulated when there is #a*ag! to a "loo# !$$!l'
- 9amage causes collag!n (i"r!$ to "! !+o$!# in t%! !$$!l"
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- 8latelets ra+i#l& $tic=to the !+o$!# collag!n (i"r!$and these platelets release a clotting
factor called throm#oplastin (enyme) that starts the cascade"
- -n the presence of calciu* ion$ and ita*in K throm#oplastin catal&$!$ the conversion of
prothom#in (inactive plasma protein) to an !n9&*!called throm#in (an active plasma protein)"
- Throm#in (enyme) catalyses the conversion of (i"rinog!n(solu#le plasma protein) into fi#rin
(insolu#le plasma protein)"
- Fi#rin forms a mesh that traps #lood cells and platelets to form a #lood clot"
C"
% cascade effect is a se,uence of events in which each event produces the circumstances
necessary for the initiation of the next event"
.uggest t)o differences #etween fi#rinogen and fi#rin" Fi#rinogen is glo#ular (spherical) and fi#rin is fi#rous (long)"
Fi#rinogen is solu#le and fi#rin is insolu#le
They are of different sies
.ummary of #lood clotting process
%: 8latelets stic4 to exposed collagen fi#res in the damaged wall of artery
C: Throm#oplastin is released
3: Jitamin A
9: 3alcium ions
0: 8rothrom#in
F: Throm#in
>: Fi#rinogen
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1" 3lot formation
2" arrowing of the artery
+" 6oss of elasticity in the artery
T%! a"o! t%r!! i**!#iat! con$!3u!nc!$ o( at%!ro$cl!ro$i$ cau$! Hig% "loo# +r!$$ur!'
Ho) at%!ro$cl!ro$i$ #!!lo+$
1" Da*ag! to t%! !n#ot%!lial liningdue to %ig% "loo# +r!$$ur!and toin$in to#acco smo4e"
.' In(la**ator& r!$+on$!5 this is increased flow of #lood to the damaged area to #ring in a lot of
)%it! "loo# c!ll$'
+" The white #lood cells cau$!c%ol!$t!rolto #uild up in the damaged area to form atheroma"
'" Pla3u! (or*ation5 calcium salts and fi#rous tissue accumulate hardening the atheroma to form a
%ar# an# un!!n $)!lling called a +la3u!on the inner wall of the artery"
E" Rai$!# "loo# +r!$$ur!5 this is due to formation of pla,ue formation of clot on the pla,ue loss of
elasticity of artery and narrowing of the lumen of the artery"" .elf!perpetuating (8ositive feed#ac4 mechanism) ! the formation of pla,ue through atherosclerosis
is a self perpetuating process (positive feed#ac4)" This is #ecause pla,ue raises #lood pressure and
this raised #lood pressure causes endothelial damage and the damaged endothelium cause the
formation of pla,ue that further raises #lood pressure hence causing 3J9s"
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amage to endothelial lining due to HBP and toxins from toa!!o smo"e
#aised lood $ressure
%n&ammator' res$onse ()B*s mo+e into the dama
-arro.ing of arter'
/theroma formation due to a uilding u$ of !hole
Plaue formation due to uild u$ of !al!ium salts and rous tissue
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*D
Peri$heral as!ular Disease (PD,*oronar' Heart Disease (*HD,tro"e (*ereral infar!tion,
(*ereral infar!tion,
/rrh'thmias Heart failureHeart atta!" ('o!ardial infar!tion, /ngina Pe!toris
mallest Heart /tta!"edium Heart /tta!"argest Heart atta!" (*ardia! arrest,
%s!hemi! Hemorrhagi! ransient %s!hemi!
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T%ro*"o$i$ -clot (or*ation/
There are two ways of forming a clot;
1" Through atherosclerosis i"e" a clot is formed on a rough surface of a pla,ue to #loc4 the
artery"
2" 9irect formation of a clot 5 platelets come into contact with damaged endothelium and
trigger clot formation"
T&+!$ o( clot$ in t%! art!ri!$
1" Throm#us 5 does not move along with #lood hence it is stationary"
2" 0m#olus 5 carried #y the #lood from the origin to elsewhere to cause #loc4age or narrowing
of the artery"
An!ur&$*
- This is the )!a=!ning o( t%! )all o( an art!r&which produces a "alloon li=! "loo# (ill!#
$)!llingformed #ehind a pla,ue with a clot on its surface"
- %neurysm (#alloon li4e #lood filled swellings) fre,uently #urst leading to hemorrhage and
therefore loss of #lood to the region of the #ody served #y that artery"- % #rain aneurysm is 4nown as cere#rovascular accident (3J%) or stro4e"
H!art attac= -*&ocar#ial in(arction/
- This is a $u##!n an# $!!r! c%!$t +aindue to the death of part of the heart muscle"
- The death is due to lac4 of oxygen in these heart muscles as a result of #loc4age of coronary
artery #y clot or pla,ue
- There are + forms of heart attac4;
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1" 6argest heart attac4 (cardiac arrest)" -t occurs if #loc4age happens in one of the coronary
arteries (Bight or left) #efore it #ranches so that a large area of heart muscle dies"
2" /edium heart attac4 5 #loc4age is in one of the #ranches of the right or left coronary
artery"
+" .mallest heart attac4 5 #loc4age is in the further #ranched #lood vessels causing the death
of a small tissue of the heart"
T%! t)o *aor (actor$ t%at can cau$! #!at% a$ a r!$ult o( %!art attac= ar!>
1" 3ardiac arrest
2" -f medical attention is delayed"
T%! $&*+to*$ o( t%! %!art attac= ar!;
1" .hortness of #reath
2" %ngina pectoris+" %rrhythmia 5 the heart #eats irregularly
'" Fatigue
E" -ndigestion
T%! t)o *aor $t!+$ to "! ta=!n )%!n &ou $u$+!ct $o*!on! i$ #!!lo+ing or %aing a %!art
attac= ar!>
1" >ive them 2 full strength aspirin ta#lets to stop #lood clotting i"e" the aspirin #ursts the
clot
2" 3all an am#ulance"
;u!$tion
The pla,ue often increases in sie and can #loc4 the artery" -f the artery supplying
#lood to the heart #ecomes #loc4ed #lood no longer flows to the heart muscle cells"
S%ortl& a(t!r t%! lo$$ o( "loo# (lo), %!art *u$cl! c!ll$ $to+ contracting an#
$tart to #i!' -n the heart muscle cells energy (%T8) is made availa#le from
respiration" The graph #elow shows how the energy (%T8) availa#le to heart muscle
cells changes with time after the loss of #lood flow"
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(i) Ising the information in the graph #!$cri"!how the energy (%T8) availa#le to the
heart muscle cells changes with time after the loss of #lood flow"-./
decrease in %T8 with time
drop in the fall of %T8 gets less with time
manipulation of figures e"g" from to * minutes the %T8 dropped #y 1
(ii) .uggest why there are changes to the availa#le energy (%T8) in the heart muscle cells
following the loss of #lood flow"-./
less oxygen availa#le
less respiratory su#strate glucose
less aero#ic respiration
(iii) %#out * minutes after the loss of #lood flow the %!art *u$cl! c!ll$ no long!r
contract'%fter a#out 2 minutes the %!art *u$cl! c!ll$ "!gin to #i!" Ising the
information in the graph and your own 4nowledge suggest explanations for the timings
of these two events"-4/
due to anaero#ic respiration in the heart muscle lactic acid #uilds up which inhi#its
respiratory enymes reducing respiration hence reducing %T8 production" .o at *
minutes there is in$u((ici!nt ATP (or contraction >
after 2 minutes the %T8 levels ar! too lo) to $u$tain c!ll $urial >
(iv) -f #lood flow is restored within + minutes *o$theart muscle cells will eventually
recover" .uggest an explanation for this recovery" -./
restored #lood flow provides muscle cells with oxygen and removes lactic acid
aero#ic respiration restarts and produces more %T8 for muscle contraction"
-Total (or ;u!$tion 6 2. *ar=$/
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Angina +!ctori$
- This is a $!!r! c%!$t +ainthat is usually experienced during igorou$ !!rci$! -!!rtion/ as a
result of narrowing of coronary arteries"
- The pain starts when exercising #ut stops when the exercise stops"
- The pain is due to lactic acid produced during anaero#ic respiration in the heart muscle"
- %naero#ic respiration is due to shortage of oxygenated #lood as a result of narrowing of a
coronary artery"- -t does not cause death of heart muscle"
- -t is a strong symptom for a heart attac4"
- The symptoms of %ngina pectoris are;
1" .evere chest pain that extends to the left arm shoulder and $aw"
2" .hortness of #reath"
T%! (ollo)ing (actor$ +r!!nt Angina +!ctori$>
1" 6ow fat diet"
2" Begular exercise"
+" 6osing weight"
'" .top smo4ing"
T%! $&*+to*$ o( angina +!ctori$ can "! tr!at!# a$ (ollo)$>
1"
-nsertion of a coronary stent
Heart transplant %ngioplasty
Angio+la$t&is the techni,ue of *!c%anicall& )i#!ning narro)!# or o"$truct!#
art!ri!$'
% coronar& $t!ntis a tu#eplaced in the coronary arteriesthat supply the heart to
4eep the arteries open in the treatment of coronary heart disease"
Stro=! -c!r!"ral in(arction/
This is the #!at% o( t%! +art o( "rain ti$$u!caused #y #ursting (Hemorrhagic) or #loc4age
(-schemic) of an artery that supplies the #rain with oxygenated #lood"
- Isually the #loc4age of an artery is #y a #lood clot formed #y atherosclerosis (a clot on top a
pla,ue)"
- -f the #loc4age affects one of the *ain art!ri!$leading to the #rain a very serious stro4e
occurs that may lead to death" However if #loc4age affects smaller arterioles leading to the#rain the effect may #e less severe"
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- The $&*+to*$ o( $tro=! a++!ar !r& (a$tand the #a*ag! %a++!n$ !r& 3uic=l&'
- The symptoms of stro4e include;
(i) um#ness
(ii) 9iiness
(iii) 3onfusion
(iv) .lurred speech
(v) 6oss of vision usually in one eye
(vi) 8aralysis of one side of the #ody with a drooping hand leg or eyelid or dri##ling mouth"- The ,uic4 treatment for stro4e that may help the patient to survive is giing clot "ur$ting
#rug$ $uc% a$ a$+irin"
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Ri$= (actor$ (or car#ioa$cular #i$!a$! -CD/
- Bis4 is the pro#a#ility of the occurrence of an unwanted event or outcome"
- There are two types of ris4s;
1" 8erceived ris4
2" %ctual ris4
P!rc!i!# ri$=
- % ris4 that is Mthought ofD and can #e underestimated or overestimated"
- 8eople will overestimate the perceived ris4 if the ris4 is;
a) -mpose sudden changes where the conse,uences are severe"
#) -nvoluntary (not under our control)
c) ot natural
d) Infamiliar
e) 9readed"
- % lot is 4nown a#out the effect of diet exercise and smo4ing on the ris4 of 3J9" Cut many
people do not change their lifestyle due to +!rc!+tion o( ri$=" This perception of ris4 is
affected #y;
a) Own experience
#) -na#ility to assess ris4s well
c) 8eer pressure
d) Fatalistic ideology (what is destined to happen must happen)"
e) Bemoteness of the li4ely conse,uences"
Actual ri$=>
- T%i$ i$ )%at actuall& %a++!n$>
- The factors that increase the actual ris4 of suffering from 3J9s are;
a) >enetic
#) >ender
c) %ge
d) 9iete) High #lood pressure
f) .mo4ing
g) -nactivity
h) O#esity
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The a#ove factors can #e divided into three"
1" The ones that can "! alt!r!# "!cau$! t%!& ar! li(!$t&l! (actor$" These include
a) 9iet
#) .mo4ing
c) High #lood pressure
d) -nactivity
e) O#esity
2" Factors that cant "! alt!r!#and they include;
a) >enetic
#) gender
c) age
+" Factors that have lifestyle and genetic components"
High #lood cholesterol
High #lood pressure
O#esity
9ia#etes
- % li(!$t&l! (actoris the one that is affected #y the way we live e"g" physical inactivity and smo4ing
are lifestyle factors as we choose to live this way"
Ri$=$ (actor$ (or CD$ t%at cannot "! alt!r!#
2' 0!n!tic
-9ue to inheritance some people have;
a) Tendency to high #lood pressure"
#) Tendency to poor cholesterol meta#olism"
c) %rteries that are more easily damaged"
d) /utation in genes that affect relative H96 to 696 levels"
- Bis4 factors with genetic components are;
a) high #lood pressure
#) high #lood cholesterol
c) o#esityd) dia#etes mellitus
. 0!n#!r
- Oestrogen gives women some protection from 3J9s #efore menopause" %fter menopause
the ris4 in #oth sexes is a#out the same"
4' Ag!
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- Health pro#lems arise when there is excess cholesterol that has accumulated in tissues"
- 0xcess cholesterol in #lood #uild up on artery wall forming atheroma that hardens (due to
#uild up of calcium salts and fi#rous tissue) to form pla,ue" This is atherosclerosis" The
su#se,uent conse,uences of atherosclerosis include; narrowing of arteries clot formation
and loss of elasticity of arteries" %ll these lead to 3J9s"
- There are three types of cholesterol (lipoproteins);
1" 6ow density lipoproteins (696)
2" High density lipoproteins (H96)
+" Jery low density lipoproteins (J696)
Not!:
->ood and #ad cholesterol are not different to each other chemically it is the way the cholesterolis carried in the #lood that is different"
- 6ow density lipoproteins are formed from saturated fats proteins and cholesterol" They #ind
to 696 receptors on the surface of the cell $aturating t%!* $o t%at LDL$ r!*ain in t%!
"loo# in$t!a# o( "!ing a"$or"!# "& t%! c!ll$and this raises #lood cholesterol level" -t is
associated with the development of atherosclerosis and therefore it should #e maintained at
low levels"
-High density lipoproteins are formed from unsaturated fats proteins and cholesterol" Theytransport cholesterol from the #ody tissue including artery walls to the liver where it is #ro4en
down and excreted" -t reduces #lood cholesterol level hence discourages atherosclerosis and
therefore should #e maintained at high levels"
Not!:
3holesterol is not saturated fat #ut is made in the liver from saturated fats a#sor#ed from food"
Lo) #!n$it& li+o+rot!in$ -LDL$/@ "a#
c%ol!$t!rol
Hig% #!n$it& li+o+rot!in$ -HDL$/@ goo#
c%ol!$t!rol
Formed from saturated fats proteins
and cholesterol
Formed from unsaturated fats proteins
and cholesterol
They #ind to the 696 receptors on the
cell surface mem#rane which can
#ecome saturated leaving the 696s in
the #lood"
They transport cholesterol from the
#ody tissues to the liver where it is
#ro4en down and excreted"
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d) O#esity due to increased respiration that reduces #lood glucose"
- /oderate exercise that reduces ris4 include;
a) &al4ing
#) 3ycling
c) .wimming
6' Hig% "loo# +r!$$ur!
This is also called hypertension"-t damages endothelial lining of arteries causing atherosclerosis that lead to 3J9s
Bis4 increased with increase in #lood pressure"
The causes of hypertension are:!
a) >enetical (inheritance)
#) %ge 5 increased with age
c) High #lood cholesterol levels
d) High alcohol inta4e
e) .mo4ing 5 can cause production of %drenaline
f) High salt inta4e
g) .tress 5 can cause production of %drenaline
1ENEFITS AND RISKS OF TREAT
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The %30 inhi#itors are antihypertensive that inhi#it the enyme so that %ngiotensin - is not
activated lowering the #lood pressure"
To !+lain %o) ACE in%i"itor$: %30 inhi#itors have similar shape to %ngiotensin - hence fit
in the active site of the %30 acting as an active site directed inhi#itor so that there is no
conversion of %ngiotensin - to %ngiotensin --"
The side effects of %30 inhi#itors are:!
a) 9ry cough#) 9iiness due to rapid lowering of #lood pressure
c) %#normal heart #eats (%rrhythmia)
d) Beduction in functioning of the 4idney (impaired 4idney function)
;u!$tion
D!$cri"! an# !+lain %o) ACE in%i"itor$ )or='
This is an anti!hypertensive drug"
They inhi#it the enyme called %ngiotensin 3onverting 0nyme (%30) from activating ahormone called %ngiotensin - into %ngiotensin --" %ngiotensin -- hormone constricts the
arteries raising the #lood pressure"
They have similar shape to %ngiotensin - (su#strate) so that they #ind to the active site of
the %30 so that no synthesis of %ngiotensin -- and the #lood vessels remain dilated; hence
reducing #lood pressure"
This anti!hypertensive acts as %ctive .ite 9irected -nhi#itors"
Calciu* c%ann!l "loc=!r$
These are antihypertensive drugs that #loc4 the calcium channels in the muscles in the
lining of the arteries to prevent contraction of the muscle so that the #lood vessels do
not constrict and this lowers #lood pressure"
ote
The muscles are mainly found in the Tunica media
The side effects include:!
a) 9iiness due to rapid lowering of #lood pressure
#) .welling of an4les due to #uildup of fluids in the legs
c) %#normal heart rhythms
d) Flushing red in the face
e) 3onstipation
C"
8eople with heart failure ta4ing some calcium channel #loc4ers can worsen symptoms of #eing fatal"This is #ecause the heart muscle will not contract as re,uired due to lac4 of calcium ions"
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Inli4e other drugs used to treat high #lood pressure calcium channel #loc4ers are generally not
given to people who have heart failure or actual physical damage to the heart muscle"
To !+lain %o) calciu* c%ann!l "loc=!r$ )or=: 3alcium channel #loc4ers attach to the target of
a specific chemical signal and preventing the signal from reaching and activating that target" .o
calcium is prevented from entering muscle cells which in turn decreases the amount of force the
muscle can generate when contracting"
The specific targets #loc4ed #y calcium channel #loc4ers exist in high num#ers #oth on #lood
vessels and in the heart allowing the drug to exert most of its influence in these areas
Diur!tic$
They are anti!hypertensive drugs that increase the volume of urine produced #y the 4idneys and
therefore lowers the excess fluids and salts in the #ody hence lowers the #lood pressure" 9iuretics cause your #ody to produce more urine"
Irine flushes excess water and sodium out of your #ody" This lowers #lood pressure #ecause the
more you urinate the lower the volume of fluid in your #loodstream" 6ess fluid in your
#loodstream means there is also lower pressure on your artery walls" -n addition the loss of
excess sodium causes your #lood vessels to open wider" This causes further lowering of your
#lood pressure"
The side effects include:!
a) 9iiness due to rapid lowering of #lood pressure
#) ausea
c) /uscle cramps
1!ta "loc=!r$
These are anti hypertensive drugs that interfere with the normal system of controlling the heart"
They ensure that the heart does not respond to hormones that speed up the heart #eat e"g
adrenaline and therefore lowers the #lood pressure"
The side effects include:!
9iiness due to rapid lowering of #lood pressure
% #eta #loc4er is a medication that slows the heart rate and reduces the force with which the heart muscle
contracts there#y lowering #lood pressure" Ceta #loc4ers do this #y #loc4ing #eta!adrenergic receptors
preventing adrenaline (epinephrine) from stimulating these receptors"
Ceta #loc4ers can #e descri#ed as either selectiveP or nonselectiveP and vasodilatingP or nonvasodilating"P
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.elective #eta #loc4ers wor4 #y #loc4ing the effect of adrenaline in the heart #ut not in the lungs or
elsewhere in the #ody" Ceta #loc4ers that vasodilate have the effect of relaxing and widening the #lood
vessels allowing #lood to flow more easily through your arteries" This means the heart doesnNt have to pump
as hard and #lood pressure is reduced"+
;u!$tion
D!$cri"! an# !+lain %o) "!ta@"loc=!r$ (unction"
This is an anti!hypertensive drug"
They reduce #lood pressure #y preventing the heart from responding to adrenaline
hormone"
Ceta #loc4ers have similar shape to adrenaline so they #ind to adrenaline receptors on the
3./ on the heart muscle cells" .o adrenaline does not #ind hence no increase in heart rate
and this causes decrease in #lood pressure"
S&*+at%!tic n!r! in%i"itor$a$o#ilator$
! Jasodilators are anti!hypertensives that act directly on smooth muscles in #lood vessel
walls to ma4e #lood vessels widen (dilate)"
! Cy widening the arteries these drugs allow #lood to flow through more easily reducing
#lood pressure"
! .o your heart doesnNt have to pump as hard and your #lood pressure is reduced"
;u!$tion
D!$cri"! an# !+lain %o) a$o#ilator$ -$&*+at%!tic n!r! in%i"itor$/ r!#uc! "loo# +r!$$ur!'
They prevent the muscle fi#res in the Tunica mediaof arteries from responding to the
nerve impulse hence no contraction and therefore no constriction so that the arteries
remain dilated reducing #lood pressure"
TREAT
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How do statins wor4K
i) They act as active site directed inhi#itors #y #inding to the active site of H/>!3o%
reductase hence lower #lood cholesterol level"
ii) %dditional enymes in the liver cell sense that cholesterol production has decreased
and respond #y creating a protein that leads to an increase in the production of 696
receptors" These receptors relocate to the liver cell mem#ranes and #ind to passing
696 and J696 (very low density lipoprotein)" The 696 and J696 then enter the liver
and are digested" This increase H96s"
The a#ove 2 functions of plant statins reduce the ris4 of developing atherosclerosis hence
reduces ris4 of 3J9Ds
-n patients who have 3J 9 treatment with statins they reduce the ris4 of heart attac4 #y
upto ++G-n people who donDt have 3J9 #ut have elevated #lood cholesterol levels statins lower total
696 cholesterol #y more than 2G and the ris4 of 3J9Ds #y a similar percent
The side effects are very rare when using statins" However the side effects include:!
a) astro 5 intestinal pro#lems e"g" constipation
d) Bespiratory cancer
e) Beduced vitamin inta4e
0xplain how lowering #lood cholesterol levels can reduce the ris4 of 3J9! 6ess cholesterol in the #lood to #uild up on artery wall (atheroma)
! Hence less li4ely to develop atherosclerosis! The su#se,uent conse,uence of atherosclerosis are narrowing of arteries
ischaemia (restriction of #lood flow) decrease in flow of #lood to the heart high
C8 clot formation loss of elasticity
N'1' C%ol!$t!rol: "!lo) 6 **ollitr! i$ t%! "!$t> 6'.@7'. "or#!ring %ig% ri$=> a"o! 7'.
%ig% ri$='
TREAT
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a) .omeone had a heart attac4 or stro4e
#) .omeone is identified as #eing at a ris4 of one heart attac4 or stro4e
c) .uch people are given drugs to prevent platelets aggregation and clotting in the artery
A/ PLATELET A00RE0ATION INHI1ITORY DRU0S
2' A$+irin
8revents platelets from aggregation #y reducing stic4iness of platelets hence reduces clot
formation"
The side effects of using aspirin are
a) -rritates the stomach lining
#) Cleeding in the stomach
c) .ome people are allergic to it"
d) ot effective in some people
e) 8artially effective in some people"
.' Clo+i#ogr!l -t is an alternative platelet aggregation inhi#itory drug to aspirin" The #enefits may #e
greater than with aspirin for some patients #ut the ris4 of #leeding is higher than with
aspirin"
4' A co*"in!# tr!at*!nt#ut has a greater ris4 of stomach #leeding than even when aspirin is
used alone"
1/ ANTI COA0ULANT DRU0S SUCH AS WARFARIN
This is an anticoagulant dug that interferes with the synthesis of prothrom#in
hence prevents #lood clotting
-t can #e ta4en orally
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O1ESITY INDICATORS
! O#esity occurs when one ta4es more energy than re,uired #y the #ody" The excess energy
is converted into fat and stored in the #ody"
! O#esity can #e inherita#le"
! The side effects of o#esity are;
a) 9ia#etes
#) High #lood pressure
c) 3J9s
d) /
(1"E)2
! The following ta#le gives the C/- and the corresponding status
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! %n individual 0%B for energy is determined #y multiplying the C/B #y the 8%6
0%B @ C/B x 8%6
5' Di!tar& r!(!r!nc! alu! -DR/
! -n the IA 9BJs are estimates of the re,uirements of energy and arenDt recommendations
for individuals" These include:!
EAR@ C/B x 8%6
LRNI@ low reference nutrient inta4e
HRNI5 high reference nutrient inta4e
! These estimates effectively provide a range of values within which a healthy #alanced diet
should fall"
En!rg& "alanc! En!rg& i*"alanc!
a/ En!rg& "alanc!
- 0nergy #alance is when the #odyDs energy re,uirements is e,ual to energy inta4e hence
there will #e no underweight or overweight concern"
"/ En!rg& i*"alanc!
- 0nergy im#alance is when one consumes more or less energy than the #odyDs re,uirements
leading to overweight andor o#esity or underweight respectively"
- O#esity or overweight increases the ris4 of 3J9s due to high #lood pressure high
cholesterol level leading to 3J9s" -n addition dia#etes and $oint pro#lems may set in due to
o#esity or overweight"
- For underweight the #ody is wea4 and can #e su#$ected to various diseases"
;u!$tion
/artin a mason weighs 4g" The human #asic energy re,uirement is '4
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@ 1124< day!1
(iv) 3alculate his energy #alance;
@ 1+ 5 112
@ !1'24< day!1
(v) 3onclusion; He loses weight"
POPULATION STUDIES IN RISK FACTORS
E+i#!*iolog&
- 0pidemiologists are scientists who carry out research to determine the ris4 factors forhealth"
- There are two 4inds of epidemiological studies;
a) 3ohort studies
#) 3ase!control studies
Co%ort $tu#i!$
- The main features are:!
6arge num#er of people is o#served"
-t ta4es long period of time"
T%!& ar! *onitor!# to $!! i( t%!& #!!lo+ t%! con#ition un#!r $tu#&'
Those that develop the condition are put in one group those who donDt in another
group"
Jarious ris4 factors that the su#$ects (people) have #een exposed to are loo4ed out
#y interviewing them"
3orrelations and causations are identified"
The disadvantages of Co%ort $tu#i!$ are;
1) 6arge num#er of people is o#served"
2) -t ta4es long period of time"+) -t is expensive
Ca$!@control $tu#i!$
The main features of case!control studies are:!
% group of people with the condition (case) is compared with a group that does not have
(control)
8ast history is then investigated to identify factors leading to one group having the disease
and the other not" -tDs very important to match the control with the case group e"g" age and gender"
A 0OOD STUDY
-t is the one with the following features;
.ample should #e representative to avoid #ias"
.ample sie is large" -n many diseases only a low percentage of the population has the
condition so a large sample may contain a small num#er of individuals with the condition"
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Jaria#les should #e controlled when selecting cohort or control groups" This is one of the
most difficult aspects of this 4ind of study since human #eings are so varia#le in terms of
genes and environment" /easurement techni,ues involve ,uestionnaire in order to
standardie the measurements"
N1
- -n any good study valid and relia#le data should #e collected"a) Jalid data 5 data that accurately measures what they are supposed to"
#) Belia#le data 5 can #e replicated"
Error$ in la" !+!ri*!nt$
- %ll experiments are su#$ected to errors"
- These errors could #e:!
-i/ S&$t!*atic !rror$
- Jalues differ from the true value #y the same amount" 0xamples of systematic errors
include;a) 0rrors due apparatus e"g" a #urette or pipette have an error in its volume"
To solve this error one can add su#$ect a certain volume e"g" 1cm+
#) The experimenter reads the volume at the wrong place each time so under! or over!
estimating the true volume at each time"
-ii/ Ran#o* !rror$
- Jalues are lying randomly a#ove or #elow a true value
- They are mainly experimenterDs errors- 0xamples include;
a) The end point of a colour change is mis$udged"
#) The vitamin 3 canDt #e added #y less than a drop at a time and so sometimes the next
drop may #e too much and other times too little"
c) Failure to rinse #eetroot dis4s well"
;u!$tion:
--n vitamin 3 experiment
1" 6ist the precautions to #e ta4en when carrying out the vitamin 3 experiment"2" 6ist ways through which vitamin 3 is lost from food"
+" 9escri#e how you would compare the vitamin 3 of + different vegeta#les"
;u!$tion$ on CD$
1)
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N1
- -f the phospholipids molecules are tightly pac4ed in water they either form:
1" /onolayer:! with hydrophilic heads in the water and hydropho#ic fatty acid tails in the air"
2" /icelles: % micelle is a structure formed #y a cluster of molecules with #oth hydropho#ic
and hydrophilic ends when placed in water" -n a micelle all the hydrophilic heads point
outwards hence face the water and all the hydropho#ic fatty acid tails point inwards (are
hidden inside) i"e" non polar environment"
N1
- 8hospholipid cause fluidity in the mem#rane while cholesterol controls fluidity""
C%ol!$t!rol
- The structure of cholesterol is:!
- -n the cell surface mem#rane cholesterol has 2 functions;
1" 3ontrol fluidity so that the cell mem#rane is not too fluid or too rigid
2" 8rovides mechanical strength to the cell mem#rane" Those that do not #rea4
easily
0l&coli+i#$
- % >lycolipid is a phospholipid attached to car#ohydrate"- -t is found only on the outer part of the phospholipid #ilayer (next to the tissue fluid)"
- -ts functions are:!
a) 3ell to cell recognition 5 to identify non self and self cells"
#) 3ell adhesion
c) %cts as receptors
d) %cts as antigens
Prot!in in t%! c!ll $ur(ac! *!*"ran!
- There are different types of protein in the cells" These include;
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a) 8eripheral protein
#) -ntegral protein
- %ll these proteins are found on and in the the cell surface mem#rane
a/ P!ri+%!ral +rot!in$
- These are attached to the surface of phospholipids #ilayer"
"/ Int!gral +rot!in$
- These are em#edded in the phospholipid #ilayer" They include:
1" Those em#edded in the inner and outer phospholipid layers"
2" Trans!mem#rane proteins" They span through the phospholipid #ilayer so that they are
exposed at #oth ends" These are:!
a) 3hannel proteins which are either gated or fixed proteins"#) 3arrier proteins which are glo#ular proteins"
c) .ome glycoproteins! % car#ohydrate attached to a protein (same
functions as glycolipid)
Rol!$ o( +rot!in$ in t%! c!ll $ur(ac! *!*"ran!
1" Transport of su#stances
This is carried #y channel and carrier proteins
2" .tructure of proteins
They all give strength to the cell mem#rane
+" 3ell to cell recognition #y the glycoprotein
'" 3ell to cell adhesion #y glycoproteins
E" .ome proteins are enymes hence they are called mem#rane #ound enymes e"g" sucrase
enyme in the cell surface mem#rane of intestinal cells"
" They act as hormone #inding sites i"e" hormone receptors
" They are electron carriers in the mem#rane
*" .ome act as antigens"
Car"o%rat!$ in t%! c!ll $ur(ac! *!*"ran!
- These car#ohydrates are polysaccharides
- They occur either in association with proteins (glycoproteins) or lipid (glycolipids)
- >lycoproteins and glycolipids are collectively 4won as glycocalyx
- The roles of glycocalyx are:!
a) 3ell to cell recognition
#) 3ell to cell adhesion
c) %ct as receptorsd) %cts as antigens
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Flui# *o$aic *o#!l o( t%! $tructur! o( t%! c!ll *!*"ran!
This is currently an accepted model of the structure of the cell mem#rane"
The mem#rane is fluid #ecause:
The phospholipids move around the mem#rane ma4ing the cell mem#rane to #e constantly in
motion"
The mem#rane is mosaic #ecause:
9ifferent types of proteins lie among the phospholipids in the mem#rane"
;u!$tion
0xplain why a mem#rane may #e more fluid when it contains more unsaturated fats"
Insaturated fatty acids contain at least one dou#le #ond in the car#on chainThe more the unsaturated lipids there are in the mem#rane the more fluid the mem#rane
is"
Rol! o( (lui#it& in *!*"ran!$
8hospholipids in mem#ranes are in fluid state"
The importance of fluidity of the mem#ranes are:
a) %llows mem#rane to change shape i"e" during active transport and facilitated diffusion"
#) %llows vesicles to #e pinched off from the mem#rane e"g" during endocytosis"
c) %llows vesicles to fuse with the mem#ranes during exocytosis"
Ei#!nc! t%at %a! "!!n i*+ortant in "uil#ing u+ t%! (lui# *o$aic *o#!l
a) The mem#rane is fluid;
1" /em#ranes $oin when the cells fuse together"
2" 3hange in position of mar4ed proteins (they intermingle or mix) when cells fuse"
+" .ealing of the mem#rane after puncturing it with a fine needle"
'" Fusion of vesicles and mem#rane during exocytosis"
E" Crea4age of mem#rane during endocytosis"
#) The mem#rane is a phospholipid #ilayer1" 8hospholipids at an airwater surface form a monolayer with hydrophilic heads in the
water and hydropho#ic tails in the air; so the phospholipids form a #ilayer with the
hydropho#ic tails hidden away from the solution and the hydrophilic heads in the
solution"
2" 6ipids extracted from red #lood cells cover an area of a#out twice the sie of the cell;
so the mem#rane must #e a phospholipid #ilayer"
c) 8roteins are carriers in the mem#rane
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1" 6arge uncharged molecules and ionic molecules can only cross the mem#rane if protein
carriers and protein channels exist; so there are protein molecules in the phospholipid
#ilayer that act as carries and channels respectively"
d) 6arge part of the mem#rane is made up of lipids"
1" 6ipid solu#le su#stances pass through the mem#rane more easily than other su#stances;
so a large part of the mem#rane must #e made up of lipids"
;u!$tion
1" 9escri#e the role of fluidity of mem#ranesK
1" -t allows the mem#rane to change shape during active transport and facilitate diffusion"
2" %llows vesicles to #e pinched off from the mem#rane during endocytosis"
+" %llows vesicles to fuse with the mem#ranes during exocytosis"
2" 9escri#e what is meant #y fluid mosaic model
- -t is fluid #ecause the phospholipids move around the mem#rane ma4ing the
cell mem#rane to #e constantly in motion"
- -t is mosaic #ecause different types of proteins lie among the phospholipids
in the mem#rane"
+" /em#ranes with more unsaturated fatty acids are more fluid" 9iscussK
- They have dou#le 3!3 #onds in the chain that would cause 4in4ing hence more
fluid"
'" &hy do phospholipids form a #ilayer and not a monolayer in the mem#raneK
- This is due to the nature of the phospholipids whose phosphate heads are
hydrophilic hence face polar environments (tissue fluid and cytoplasm) and
the fatty acid tails are hydropho#ic hence face inwards (non polar
environment)
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TRANSPORT ACROSS
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The concentration of the + mineral ions in a seedling are determined e"g nitrates (O+!E units
phosphates (8O'+!E units and magnesium (/g2)E units
The concentration of these ions in the #ea4er are also determined e"g nitrates 5 1 units
phosphates 5 1 units and magnesium 5 1 units"
The seedling is placed in the #ea4er and left for days"
The results are shown #elow"
O+! 8O'+! /g2Cea4er
8lant (seedling)
"E
"E
*"
"
?"
"
The results shows that
1" The ions are #eing a#sor#ed through facilitated diffusion #ecause with nitrates e,uili#rium
has #een achieved
2" The a#sorption of the nitrate ions (O+!) is faster than other minerals
+" 9ue to different concentration of the ions inside the plant the + ions are transported #y
different channel proteins i"e channel protein are specific to ions"
C
-n facilitated diffusion no meta#olic energy is used and the movement of ions is down the
concentration gradient"
"/ Carri!r +rot!in$
They transport large polar molecules such as amino acids and glucose" These carrier proteins are
specific for particular molecules" Once a carrier protein has pic4ed up a molecule it changes shape
and act as a pore for the molecule to travel through the mem#rane" There is no use of meta#olic energy
and the movement is down the concentration gradient
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0xample of diffusion include:
1" >as exchange in the lungs #etween the alveoli and the capillaries"
2" >as exchange in the leaves of flowering plants #etween the air spaces and the spongy
mesophyll tissue and the mesophyll cells
The re,uirements for diffusion facilitated diffusion to occur are
1" 3oncentration gradient of the su#stance
2" 8ermea#le mem#rane
O$*o$i$
This is the passive movement of molecules of water down their concentration gradient through a
partially permea#le mem#rane"
Osmosis is due to the random movement of water molecules across the mem#rane" -f solute
molecules are present water molecules from hydrogen #onds with them and this reduces the
movement of these water molecules"
0xamples of osmosis include:
a) %#sorption of water molecules #y animal and plant cells
#) %#sorption of water molecules #y the plant roots from the soil
D!$cri"ing conc!ntration$
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2' I$otonic $olution
This is the solution that has the same osmotic concentration of the solution as the cell i"e there is
e,uili#rium hence no net movement (no osmotic gradient)
.' H&+!rtonic $olution
This is the solution with the higher concentration of solutes than the cell and therefore water will
move from the cell to the solution and the animal cell shrin4s (crenated) and the pant cell shrin4s
(#ecomes flaccid) and is finally plasmolyed (cell mem#rane moves away from cell wall)"
The num#er represents solute not water
%rrow shows movement of water
4' H&+notic $olution
This is the solution with less solute than the cell and thus it has more water then the cell" .o
water will move from the solution into the cell causing the cell to #ecome turgid (full of water) and
finally the animal cell #ursts #ut the plant cell remains turgid as
