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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.