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Chapter 3hapter 3
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The movement ofsubstances across
the plasma membrane
PassiveTransport
ActiveTransport
SimpleDiffusion
Osmosis FacilitateDiffusion
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Learning outcomesLearning outcomes
At the end of this lesson, student willAt the end of this lesson, student will
be able to:be able to:
State orally 2 over 3 types ofState orally 2 over 3 types ofpassive transport correctly.passive transport correctly.
List down in written form at least 3List down in written form at least 3
out of 5 the comparison of passiveout of 5 the comparison of passive
transport and active transport intransport and active transport in
correct and precise way.correct and precise way.
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Passive TransportPassive Transport
The movement of particles (moleculesThe movement of particles (molecules
or ions) within gas or liquid from aor ions) within gas or liquid from a
region of higher concentration to aregion of higher concentration to a
region of lower concentration.region of lower concentration.The processThe process does not requiredoes not require
expenditure of energy from ATP.expenditure of energy from ATP.
Examples are simple diffusion, osmosisExamples are simple diffusion, osmosisand facilitated diffusion.and facilitated diffusion.
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Simple DiffusionSimple Diffusion
Define as net movement ofDefine as net movement ofmolecules or ions from a region ofmolecules or ions from a region of
higher concentration to a region ofhigher concentration to a region of
lower concentration, that is, to movelower concentration, that is, to movedown a concentration gradient untildown a concentration gradient until
an equilibrium is reached.an equilibrium is reached.
Physically can be observed in liquidsPhysically can be observed in liquids
or gases.or gases.
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Modelling diffusionModelling diffusion
The diffusion state continues until the system hasThe diffusion state continues until the system hasreached a dyanamic equilibrium where thereached a dyanamic equilibrium where theconcentration gradient no longer exist.concentration gradient no longer exist.
before diffusion after diffusionafter diffusion
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Osmosis: the diffusion ofOsmosis: the diffusion of
waterwater It define as theIt define as the diffusion of waterdiffusion of water
molecules from amolecules from a region higherregion higherwater concentration to awater concentration to a region ofregion of
lowerlower water concentration throughwater concentration throughsemi-permeable membrane.semi-permeable membrane.
The semi-permeable membrane isThe semi-permeable membrane is
permeable to water BUT impermeablepermeable to water BUT impermeableto certain solutes such as sucroseto certain solutes such as sucrose
molecules.molecules.
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Examples:Examples:Absorption of water from soil solution byAbsorption of water from soil solution by
plant root hairsplant root hairsReabsorption of water by kidney tubuledReabsorption of water by kidney tubuled
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The process of osmosis:The process of osmosis:
Semi-permeable membraneprevents the movement of
larger solute molecules
Only watermolecules can passthrough the poresin the semi-permeable
membrane.
Watermolecules
Solutemolecules
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The movement of molecules or ionsThe movement of molecules or ions
down their concentration gradientdown their concentration gradient
assisted by transport proteins, namelyassisted by transport proteins, namely
thethe carrier proteinscarrier proteins oror porepore(channel) proteins(channel) proteins..
The process isThe process is passivepassiveand does notand does not
require expenditure of energy by therequire expenditure of energy by thecell.cell.
Facilitate diffusionFacilitate diffusion
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Pores proteins form pores orPores proteins form pores or
channels through which smallchannels through which small
dissolved particles, esp. ions candissolved particles, esp. ions candiffuse across plasma membrane.diffuse across plasma membrane.
Pores have specific interiorPores have specific interior
characteristics that only allowcharacteristics that only allowspecific ions to pass through them.specific ions to pass through them.
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Activity 1Activity 1
True or FalseTrue or False
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1.1. Passive transport across the plasma membranePassive transport across the plasma membrane
ensures the cell get its supply of oxygen, glucoseensures the cell get its supply of oxygen, glucose
and amino acids.and amino acids. (T/F)(T/F)2.2. Substances that are required by cells and those toSubstances that are required by cells and those to
be eliminated from cells can move across thebe eliminated from cells can move across the
plasma membrane.plasma membrane. (T/F)(T/F)
3.3.
The plasma membrane is semi-permeable.The plasma membrane is semi-permeable.
(T/F)(T/F)4.4. The fluid mosaic model is made up of a lipidThe fluid mosaic model is made up of a lipid
bilayer with amino acids scattered in it.bilayer with amino acids scattered in it. (T/F)(T/F)
5.5. The lipid bilayer and protein molecules in theThe lipid bilayer and protein molecules in the
plasma membrane are static.plasma membrane are static. (T/F)(T/F)
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6.6. Passive transport is simple diffusion andPassive transport is simple diffusion and
facilitated diffusion across a membrane.facilitated diffusion across a membrane.
(T/F)(T/F)7.7. Passive transport occurs down thePassive transport occurs down the
concentration gradient.concentration gradient. (T/F)(T/F)
8.8. Specific proteins facilitate diffusion acrossSpecific proteins facilitate diffusion across
the plasma membrane.the plasma membrane. (T/F)(T/F)
9.9. Digested food diffuses from the ileum intoDigested food diffuses from the ileum into
the capillaries in the villus by simplethe capillaries in the villus by simple
diffusion.diffusion. (T/F)(T/F)
10.10. Passive transport is the pumping of mineralPassive transport is the pumping of mineral
salts into the root hairs down thesalts into the root hairs down the
concentration gradient.concentration gradient. (T/F)(T/F)
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Active TransportActive Transport
Define as the movement of molecules orDefine as the movement of molecules or
ions across the plasma membrane againstions across the plasma membrane against
their concentration gradient.their concentration gradient.
The process requires carrier proteins withThe process requires carrier proteins withspecific binding sites.specific binding sites.
Use energy in the form of ATP (generatedUse energy in the form of ATP (generated
during respiration in mitochondria).during respiration in mitochondria).
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Active transport results in theActive transport results in the
accumulation of or elimination ofaccumulation of or elimination of
molecules and ions from the cells.molecules and ions from the cells. In animal cells, the concentration ofIn animal cells, the concentration of
potassium ions inside the cell is alwayspotassium ions inside the cell is always
higher than the concentration outsidehigher than the concentration outsidethe cells. These carrier proteins, alsothe cells. These carrier proteins, also
called sodium-potassium pumps.called sodium-potassium pumps.
Help to maintain the concentrationHelp to maintain the concentration
gradients by pumping sodium ions out ofgradients by pumping sodium ions out of
the cell and potassium ions into the cell.the cell and potassium ions into the cell.
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Activity 2Activity 2
ComparisonComparison
between passivebetween passive
and activeand activetransport.transport.