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1. How are the two products of glycolysis connected to the reactionsof the TCA cycle?
2 products of glycolysis Pyruvate & NADH, can be metabolized in 2 different ways depending on
cell type in which they are formed & the presence or absence of oxygen ! prese!ce of "2 in mitochondria# aerobic organisms extract large amounts of energy from
the pyruvate& NADH made during glycolysis !"# more A$%s
P$%$A'(o 'sed as a generator of ')A cycle
(n the mitochondrion, several enzymes catalyze the conversion of ")carbon
pyruvate to 2)carbon acetyl *oA, yielding a molecule of NADH and one *+2
$he acetyl *oA enters the citric acid or $*A cycle
o Process1* is transported into mitochondrial matrix across the inner mitochondrial
membrane2* decarboxylated -! forms a 2 * fragment -*H"*++). acetyl group / *+23* Acetyl group is transferred to coenzyme A to ma0e acetyl *oAwhich carries
the 2 * fragment to 1rebs cycle
+* +verall reaction %yruvate / H3-*oA / NAD/ -! Acetyl *oA / *+2 /
NADH / H/. catalyzed by a giant multienzyme complex pyruvate
dehydrogenase
o
$*A cycle is important
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- accepts metabolites from or contributes them to other pathways entry point for
catabolic mechanism regardless of nature of starting material All of cell4s
energy)providing macromolecules polysaccharides, fats, proteins brea0 down to
$*A cycle metabolites
Acetyl *oA ) brea0down product of fatty acids degraded 2 *4s at a time
in matrix fatty acids are also synthesized that way with acetyl *oA as
donor & other catabolic pathways
%roteins brea0 down to amino acids, which are catabolized & enter $*A
cycle at various sites. enter matrix via special transport systems in inner
mitochondrial membrane
o reduced coe!,y-es i! A'P for-atio! .NADH & /ADH20- are the primary product of pathway electrons they carry came from oxidized
1rebs substrates & used to ma0e A$%
-
lycolytic NADH 5nters mitochondrion via malate)aspartate shuttle reduci!g NAD
NADH 'ra!sfers electro!s to /AD /ADH2via glycerol phosphate shuttle
- 'ur!i!g NADH & /ADH2 A'P .)e-ios-osis4 Step 1
$he electrons from NADH are transferred to the electron carrier
proteins & the protons are transferred across the membrane
As electrons move from cytochrome to cytochrome, down the
electron transport chain, more protons are carried across the
membrane including the electrons from 6ADH2 *ytochrome c transfers electron to cytochrome c oxidase
complex %rotons are also transferred to the outside of he
membrane by the cytochrome c oxidase complex
$he cytochrome oxidase complex then transferred electron from
cytochrome c to oxygen, the terminal electron acceptor that
formed water as the product
$he protons generate a proton motive force across the membrane
of the mitochondrion 3ince membranes are impermeable to ions,
the protons that reenter the matrix pass through special proton
channel proteins called A$% synthase
Step 2
$he energy derived from the movement of these protons is used
to synthesize A$% from AD% and %oxidative phosphorylation
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! ase!ce of
"2 fermentation
is carried
out in
cytoplasm
2.Why is
the TCA cycleconsidered
to be the central pathwayin the energy metabolism of a cell?
o accepts metabolites from or contributes them to other pathways entry point for catabolic
mechanism regardless of nature of starting materials
o All of cell4s energy)providing macromolecules polysaccharides, fats, proteins brea0 down to
$*A cycle metabolites
Acetyl *oA ) brea0down product of fatty acids degraded 2 *4s at a time in matrix
fatty acids are also synthesized that way with acetyl *oA as donor & other catabolic
pathways
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%roteins brea0 down to amino acids, which are catabolized & enter $*A cycle at
various sites. enter matrix via special transport systems in inner mitochondrial
membrane
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3. escribe the steps by which the transport of electrons down therespiratory chain leads to the formation of a proton gradient !see"igure #.1$%
$he energy released as electrons from NADH is pass down through the complexes of the
respiratory chain ( 7 NADH dehydrogenase, ((( 7 cytochrome c reductase, and (8 7 cytochrome
c oxidase to pump protons H/ against their concentration gradient from the matrix of the
mitochondrion into the intermembrane space active tra!sport
As their concentration increases there which is the same as saying that the pH decreases, a
strong diffusion gradient is set up protons is passed through the A$% synthasecomplex
resulting the synthesis of A$%ce-ios-osisand is an example of facilitated diffusio!*
"9 A$% are made from the products of : molecule of glucose
$he process is a step6ise -ove-e!t of electro!s fro- ig e!ergy to lo6 e!ergy tat -a7es
te proto! gradie!t
$he proto! gradie!t po6ers A'P productio!N+$ the flow of electrons
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/A.html#active_transporthttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/ATPsynthase.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/D/Diffusion.html#facilitatedhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/ATPsynthase.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/D/Diffusion.html#facilitatedhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/A.html#active_transport8/10/2019 Study Exercise Biology 13-15
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$his electron transport cai! o!ly occurs 6e! oxyge! is availale *
P%")(SSo 3tep :
$he electrons from NADH are transferred to the electron carrier proteins & the
protons are transferred across the membrane As electrons move from cytochrome to cytochrome, down the electron transport
chain, more protons are carried across the membrane including the electrons from
6ADH2
*ytochrome c transfers electron to cytochrome c oxidase complex %rotons are
also transferred to the outside of he membrane by the cytochrome c oxidase
complex
$he cytochrome oxidase complex then transferred electron from cytochrome c to
oxygen, the terminal electron acceptor that formed water as the product
$he protons generate a proton motive force across the membrane of themitochondrion $he number of hydrogen atoms also called proton gradient will
build up and flow bac0 to the matrix simultaneously powering the production of
A$% and dince membranes are impermeable to ions, the protons that reenter the
matrix pass through special proton channel proteins called A$% synthase
o 3tep 2
$he energy derived from the movement of these protons is used to synthesize
A$% from AD% and % oxidative phosphorylation
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&. What is the effect of initrophenol on AT' formation by
mitochondria? Why is this case?
2,9)Dinitrophenol 2,9)DN%, or simply DN%, *;H9N2+
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#. escribe the basic structure of the AT' synthase
$he structure of A$% synthase consists of two rotary motors, labeled 6: and 6o, that are connected by a
flexible shaft
'nder normal operation, the 6o motor uses the energy stored in a transmembrane ion gradient todrive the 6: motor in reverse so that A$% is synthesized from AD% and phosphate
(n bacteria, anerobic conditions wipe out the ion gradient whereupon the 6: part becomes a
motor, using the energy of A$% hydrolysis to turn the 6o part in reverse so that it functions as an
ion pump
a* Sperical /1 ead .89: ; dia-eter< very si-ilar i! -itoco!dria & acteria# te structure
is igly co!served0 = 3>:#::: dalto!s
=oth bacterial & mitochondrial A$% synthasescontain < different polypeptides >, ?, @, ,B
with the following stoichiometry >"?"@B
> & ? subunits arranged alternately in 6: head li0e orange segments
5ach 6: contains " catalytic sites for A$% synthesis one on each ? subunit
$he subunit runs from outer tip of 6: head through central stal0 & contacts the 6#
basepiece
(n the mitochondrial enzyme, all < 6: polypeptides are encoded by nuclear DNA, made in
the cytosol & imported into mitochondrion posttranslationally
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* 'e /: ase is e-edded i! i!!er -itoco!drial -e-ra!e< co!tai!s ca!!el tat co!ducts
proto!s fro- i!ter-e-ra!e space ac7 to -atrix prese!ce of ca!!el so6! y
experi-e!t
=rea0 inner mitochondrial membrane into fragments forming membrane vesicles
submitochondrial particles0
(ntact submitochondrial particles containing A$% synthase embedded in vesicle membrane
can oxidize substrates, generate a proton gradient & synthesize A$%
(f 6: spheres are removed from particles by urea treatment, vesicle membrane can no longer
maintain a proton gradient despite continuing substrate oxidation & electron transport
%rotons translocated across membraneduring electron transport simply cross bac0 through
beheaded A$% synthase & energy is dissipated
(. escribethe structureand functionof
pero)isomes and glyo)ysome.
P(%?"S"@(
organelles found in nearly all eu0aryoticcells
single membrane microbodies found in photosynthetic cells of plants and liver and 0idney cells of
vertebrates
first discovered by C hodin in :E
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o surrou!ded y a lipid ilayer -e-ra!ewhich e!closes te crystalloid coreo the bilayer is enclosed with a plasma membrane which regulates what enters and exits the
peroxisome
o $here are at least "2 0nown peroxisomal proteins, called peroxins, which carry out
peroxisomal function inside the organelle
/u!ctio!o to rea7 do6! lo!g a!d ra!ced fatty acid cai!s# D=a-i!o acids# a!d polya-i!es
usi!g its e!,y-estransported to mitochondria where the maGority of catabolism
happen in both eu0aryotic and pro0aryotic cells. however in pro0aryotes only happen in
peroxisome wihout the mitochondriao site of cataolis- of fats a!d fat=solule vita-i!s, such as vitamin A and vitamin 1, as
well as the productio! of ile acidso for-atio! a!d degradatio! of ydroge! peroxide .H2"20are able to brea0 it down
into water H2+, is harmless to the cell and oxygen +2, can be used in the next
digestive
o help in sy!tesi,i!g plas-aloge!s a!d eterpospolipidsthat are necessary for
proper brain and lung function
o aid certai! e!,y-es 6it e!ergy -etaolis-in many eu0aryotic cells as well with
colesterol sy!tesisin animalso i!volved i! detoxificatio! of poiso! i! te cell# ger-i!ati!g seedsin the glyoxylate
cycle, potosy!tesisin leaves, and oxidatio! of a-i!esin various yeasts
"?$S"@(
also single membrane microbodies has similar structure as peroxisome but found only in plant
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cells
contains many enzymes li0e isocratic lyase, malate synthetase, glycolate oxidases, etc for
glyoxylate cycle ie, metabolism of glycolic acid
specializedperoxisomesfound inplantsparticularly in thefatstorage tissues of germinating
seeds and also in filamentous fungi
/u!ctio!so participate i! potorespiratio! a!d !itroge! -etaolis-in root noduleso contain enzymesthat i!itiate te rea7do6! offatty acidsand possess the enzymes to
produce i!ter-ediate products fro- te fats for te sy!tesis of sugarsy
gluco!eoge!esisseedling uses these sugars synthesized from fats until it is mature
enough to produce them byphotosynthesisand to generate new cell walls during growth
$. *)plain the basics of AT' formation according to the binding
change mechanism + 'aul ,oyer and -itchel'e asics of A'P for-atio! accordi!g to te i!di!g ca!ge -eca!is- Paul Boyer# )A
.19C90
1* (!ergy released y proto! -ove-e!t ca!ges active site i!di!g activity for sustrate &
producto 5nergy released by proton movement does not directly phosphorylate AD% to A$%, but it
principally changes the active site binding affinity for the A$% product
o (n an aueous environment where reactants & products are dissolved in medium, energy
is needed to drive the formation of the covalent bond lin0ing AD% with inorganic
phosphate to form A$%
o =ut when AD% & %i bind to A$% synthase catalytic site, they condense to form a tightly
bound A$% molecule without the input of additional energy
o *onsiderable energy F" 0calImole under standard conditions is needed to form A$%
when reaction occurs in water solution when AD%, %( & A$% are soluble
2* (ac active site goes successively troug 3 disti!ct co!for-atio!s tat ave differe!t
sustrate & product affi!ities te /1 co-plex as 3 catalytic sites# o!e o! eac of te 3
=suu!itso %roperties of the " ? catalytic sites in a static enzyme one not engaged in enzymatic
turnover, the different sites exhibited different chemical properties
o =oyer proposed that at any one time, each of the " sites is present in different
conformations that have differing affinities for nucleotides one in J, one in $, one in +
Joose J conformation ) AD% & %i are loosely bound
$ight $ conformation ) AD% / %( substrates or A$% product are tightly bound
+pen + conformation 7 it has a very low affinity for nucleotides allowing
release of tightly bound A$%. thus, it is considered empty
http://en.wikipedia.org/wiki/Peroxisomeshttp://en.wikipedia.org/wiki/Peroxisomeshttp://en.wikipedia.org/wiki/Plantshttp://en.wikipedia.org/wiki/Fathttp://en.wikipedia.org/wiki/Fathttp://en.wikipedia.org/wiki/Germinationhttp://en.wikipedia.org/wiki/Germinationhttp://en.wikipedia.org/wiki/Enzymeshttp://en.wikipedia.org/wiki/Fatty_acidhttp://en.wikipedia.org/wiki/Fatty_acidhttp://en.wikipedia.org/wiki/Sugarshttp://en.wikipedia.org/wiki/Sugarshttp://en.wikipedia.org/wiki/Gluconeogenesishttp://en.wikipedia.org/wiki/Photosynthesishttp://en.wikipedia.org/wiki/Peroxisomeshttp://en.wikipedia.org/wiki/Plantshttp://en.wikipedia.org/wiki/Fathttp://en.wikipedia.org/wiki/Germinationhttp://en.wikipedia.org/wiki/Enzymeshttp://en.wikipedia.org/wiki/Fatty_acidhttp://en.wikipedia.org/wiki/Sugarshttp://en.wikipedia.org/wiki/Gluconeogenesishttp://en.wikipedia.org/wiki/Photosynthesis8/10/2019 Study Exercise Biology 13-15
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3* A'P is produced y rotatio!al catalysis = o!e part of A'P sy!tase rotates relative to
a!oter parto =oyer proposedthat the > & ? subunits, which form a hexagonal ring of subunits within
the 6: head, rotate relative to the central stal0 rotational catalysis
o otation is driven by proton movement through membrane into matrix via the channel
in6# base
o $hus, electrical energy stored in proton gradient is transduced into the mechanical energy
of a rotating stal0, which is transduced into chemical energy stored in A$%