AS Biology, Cell membranes and Transport1 Transport through cell membranes.

AS Biology, Cell membranes and AS Biology, Cell membranes and TransportTransport 11

Transport through cell Transport through cell membranesmembranes

Cell videoCell video

http://www.youtube.com/watch?http://www.youtube.com/watch?v=moPJkCbKjBs v=moPJkCbKjBs cell membrane and transport (3)cell membrane and transport (3)

http://www.youtube.com/watch?v=-http://www.youtube.com/watch?v=-aSfoB8Cmic aSfoB8Cmic cell membrane – limits of life 3 minutes (2)cell membrane – limits of life 3 minutes (2)

http://www.youtube.com/watch?http://www.youtube.com/watch?v=ULR79TiUj80 v=ULR79TiUj80 fluid mosaic model (1)fluid mosaic model (1)


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For a cell to survive materials must For a cell to survive materials must enter and leave the cellenter and leave the cell

Cell membranes are selectively Cell membranes are selectively permeablepermeable

4 basic mechanisms:4 basic mechanisms:

1.1. DIFFUSION and FACILITATED DIFFUSION and FACILITATED DIFFUSIONDIFFUSION

2.2. OSMOSISOSMOSIS

3.3. ACTIVE TRANSPORTACTIVE TRANSPORT

4.4. BULK TRANSPORTBULK TRANSPORT44

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DiffusionDiffusion

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Diffusion is:Diffusion is:

movement of a substance from a high movement of a substance from a high concentration to a lower concentration.concentration to a lower concentration.

Diffusion across a membrane:Diffusion across a membrane:

Molecules move down a Molecules move down a concentration concentration gradient.gradient.

Molecules have Molecules have kinetic energykinetic energy, which , which makes them move about randomly. makes them move about randomly.

End result, molecules reach End result, molecules reach equilibrium - equilibrium - are even on both sides – no net movement are even on both sides – no net movement of molecules of molecules

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DIFFUSIONDIFFUSION

Diffusion is PASSIVE Diffusion is PASSIVE no energy is usedno energy is used


Diffusion through a membraneDiffusion through a membrane

Cell membrane

Inside cell Outside cell



Cell membrane


diffusion



Cell membrane


EQUILIBRIUM

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Rate of diffusion determined byRate of diffusion determined by4 factors:4 factors:

1.1. The steepness of the concentration gradient. The steepness of the concentration gradient. • The bigger the difference between the two sides of the The bigger the difference between the two sides of the

membrane the quicker the rate of diffusion. membrane the quicker the rate of diffusion.

2.2. Temperature. Temperature. • Higher temperatures give molecules or ions more kinetic Higher temperatures give molecules or ions more kinetic

energy. Molecules move around faster, so diffusion is faster.energy. Molecules move around faster, so diffusion is faster.

3.3. The surface area. The surface area. • The greater the surface area the faster the diffusion can take The greater the surface area the faster the diffusion can take

place. This is because the more molecules or ions can cross place. This is because the more molecules or ions can cross the membrane at any one moment.the membrane at any one moment.

The type of molecule diffusingThe type of molecule diffusing. . 1.1. Large molecules need more energy to get them to move so Large molecules need more energy to get them to move so

they tend to diffuse more slowly. Non-polar molecules diffuse they tend to diffuse more slowly. Non-polar molecules diffuse more easily than polar molecules because they are soluble in more easily than polar molecules because they are soluble in the non polar phospholipid tails.the non polar phospholipid tails.

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Molecules that diffuseMolecules that diffuse

1.1. Oxygen – Oxygen – Non-polar Non-polar so diffuses very so diffuses very quickly.quickly.

1.1. Lipid Soluble Lipid Soluble moleculesmolecules

1.1. Carbon dioxide – Carbon dioxide – Polar but very small Polar but very small so diffuses quickly.so diffuses quickly.

2.2. Water – Water – Polar but Polar but also very small so also very small so diffuses quickly.diffuses quickly.

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Facilitated diffusionFacilitated diffusion Molecules pass Molecules pass

through through protein protein channelschannels

Movement is Movement is still PASSIVEstill PASSIVE

Types of Types of molecules :molecules :

Large polar Large polar molecules molecules (glucose and (glucose and amino acids) and amino acids) and ions (Naions (Na++ and Cl and Cl -)-)


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Facilitated Diffusion through a Facilitated Diffusion through a membranemembrane

Cell membrane


Protein channel



Cell membrane


Protein channel

diffusion



Cell membrane


Protein channel

diffusion

EQUILIBRIUM


OsmosisOsmosis is is

The diffusion of water across The diffusion of water across a semipermeable membranea semipermeable membrane

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OsmosisOsmosis

Cell membrane partially permeable.

Inside cell Outside cellVERY High conc. of water molecules. High water potential.

VERY Low conc. of water molecules. High water potential.

Sugar molecule

DILUTE SOLUTIONCONCENTRATED SOLUTION

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OsmosisOsmosis


Inside cell Outside cellHigh conc. of water molecules. High water potential.

Low conc. of water molecules. High water potential.OSMOSIS

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OsmosisOsmosis



OSMOSIS

EQUILIBRIUM. Equal water concentration on each side. Equal water potential has been reached. There is no net movement of water

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Active TransportActive Transport

Active TransportActive Transport

Moves material up the concentration Moves material up the concentration gradientgradient Low to HighLow to High

Movement is not spontaneousMovement is not spontaneous Requires ATP and a protein carrierRequires ATP and a protein carrier

ATP causes conformational changes in ATP causes conformational changes in membrane protein to move molecules against membrane protein to move molecules against their concentration gradient. their concentration gradient.


Types of active transportTypes of active transport

SimpleSimple Coupled (movement dependant on protein Coupled (movement dependant on protein

binding to trigger moleucle)binding to trigger moleucle) Symports (both molecules moved in same Symports (both molecules moved in same

directiondirection

and and Antiports (moleules move in opposite Antiports (moleules move in opposite

directions)directions)

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Make the following chart:Make the following chart:

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Example disorder related to Example disorder related to transport proteinstransport proteins

BULK TRANSPORTBULK TRANSPORT http://www.youtube.com/watch?v=kfy92hdaAH0&feature=relmfu review and bulkhttp://www.youtube.com/watch?v=kfy92hdaAH0&feature=relmfu review and bulk http://www.youtube.com/watch?v=1w10R9lv7eQ&feature=relatedhttp://www.youtube.com/watch?v=1w10R9lv7eQ&feature=related

USE YOUR TEXT BOOK TO DESCRIBE USE YOUR TEXT BOOK TO DESCRIBE ENDO AND EXO CYTOSISENDO AND EXO CYTOSIS

DEFINE PHAGOCYTOSIS, DEFINE PHAGOCYTOSIS, PINOCYTOSISPINOCYTOSIS



ExocytosisExocytosis The opposite of endocytosis is exocytosis. Large molecules that are The opposite of endocytosis is exocytosis. Large molecules that are

manufactured in the cell are released through the cell membrane.manufactured in the cell are released through the cell membrane.



Endocytosis is the case when a molecule causes the cell membrane to Endocytosis is the case when a molecule causes the cell membrane to bulge inward, forming a vesicle. Phagocytosis is the type of bulge inward, forming a vesicle. Phagocytosis is the type of

endocytosis where an entire cell is engulfed. Pinocytosis is when the endocytosis where an entire cell is engulfed. Pinocytosis is when the external fluid is engulfed. Receptor-mediated endocytosis occurs when external fluid is engulfed. Receptor-mediated endocytosis occurs when the material to be transported binds to certain specific molecules in the the material to be transported binds to certain specific molecules in the membrane. Examples include the transport of insulin and cholesterol membrane. Examples include the transport of insulin and cholesterol

into animal cells.into animal cells.




Cotransport also uses the process of diffusion. In this case a molecule Cotransport also uses the process of diffusion. In this case a molecule that is moving naturally into the cell through diffusion is used to drag that is moving naturally into the cell through diffusion is used to drag another molecule into the cell. In this example glucose hitches a ride another molecule into the cell. In this example glucose hitches a ride

with sodium.with sodium.


Receptor ProteinsReceptor Proteins These proteins are used in intercellular communication. In this These proteins are used in intercellular communication. In this

animation you can see the a hormone binding to the receptor. This animation you can see the a hormone binding to the receptor. This

causes the receptor protein release a signal to perform some action.causes the receptor protein release a signal to perform some action.


Cotransport also uses the process of diffusion. In this case a molecule Cotransport also uses the process of diffusion. In this case a molecule that is moving naturally into the cell through diffusion is used to drag that is moving naturally into the cell through diffusion is used to drag another molecule into the cell. In this example glucose hitches a ride another molecule into the cell. In this example glucose hitches a ride

with sodium.with sodium.


These are carrier proteins. They do not extend through the membrane. These are carrier proteins. They do not extend through the membrane. They bond and drag molecules through the bilipid layer and release They bond and drag molecules through the bilipid layer and release

them on the opposite side. them on the opposite side.


Vesicle-mediated transport Vesicle-mediated transport Vesicles and vacuoles that fuse with the cell membrane may be utilized Vesicles and vacuoles that fuse with the cell membrane may be utilized

to release or transport chemicals out of the cell or to allow them to to release or transport chemicals out of the cell or to allow them to enter a cell. Exocytosis is the term applied when transport is out of the enter a cell. Exocytosis is the term applied when transport is out of the

cell.cell.


Cell Membrane - Function - EndocytosisCell Membrane - Function - Endocytosis The cell membrane can also engulf structures that are much too large to fit through the The cell membrane can also engulf structures that are much too large to fit through the

pores in the membrane proteins this process is known as endocytosis. In this process the pores in the membrane proteins this process is known as endocytosis. In this process the membrane itself wraps around the particle and pinches off a vesicle inside the cell. In this membrane itself wraps around the particle and pinches off a vesicle inside the cell. In this

animation an ameba engulfs a food particle.animation an ameba engulfs a food particle.

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AS Biology, Cell membranes and Transport1 Transport through cell membranes.

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