MembranesStephen Taylori-Biologynet Photo credit Plasmolysis by MNolf via

httpcommonswikimediaorgwikiFileRhoeo_Discolor_-_Plasmolysisjpg

Pre-assessmentbull What can you label on this diagram bull Can you explain three different methods of transport across a membrane

Plasma Membranebull Label the diagram with components amp functionsbull Identify components that are involved in transport

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Plasma Membranebull Label the diagram with components amp functionsbull Identify components that are involved in transport

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Plasmolysis in Elodea and in onion cells 1 Set up slides of Elodea cells and onion cells with tap water medium2 Find cells under the microscope Draw and label what you see

Include magnification You might need to try different stains 3 Draw salt solution through the slides Observe and draw the effects 4 Explain the effects of changing the salt concentration on the cells

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Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Explain passive transport across membranes by simple diffusion amp facilitated diffusion

Simple amp facilitated diffusion are passive bull No energy input is required

There is a net movement of molecules from one side of the membrane to the other bull The motion of molecules is random (Brownian motion)

bull But there is an overall general movement in one direction

This net movement is down the concentration gradient bull From areas of high concentration to low concentration

Movement is across a selectively or partially permeable membraneDependent on size or properties some molecules can cross and not others

Simple DiffusionOccurs when the moleculersquos properties allow them

pass across the membrane

Facilitated DiffusionSome molecules cannot cross easily for example if they are polar the phospholipids of the bilayer will

repel them

The rate of diffusion is affected by bull magnitude of concentration gradient

bull SAVol ratio (more membranes more transport per unit volume)

bull Length of diffusion pathway (longer journey gives slower diffusion)

Channel proteins are integral membrane proteins that pass through the membrane

Their properties allow molecules to pass through (eg polar molecules or ions)

Activation of these channels might be voltage-gated (eg in neurons) or binding-activated

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Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Active transport uses energy in the form of ATP to move molecules across a selectively permeable membrane against the concentration gradient using protein pumps

Why do this To move molecules against the concentration gradient or to create a large concentration gradient across a membrane

Protein pumps These are integral passing through the membrane They are specific ndash only working with the target molecule

What happens 1 Target molecules bind to the pump 2 ATP also binds to the pump ATP is broken releasing energy and causing a

conformational (shape) change in the protein pump 3 This conformational change pushes the molecules across the membrane4 The molecule unbinds and the pump reverts back to the original shape

Examples bull Sodium-potassium pump is used to re-polarise neurons after an action potential ready to fire again

bull Proton pumps in mitochondria generate a high concentration gradient of H+ ions ready for chemiosmosis through ATP synthase used for generating ATP

Active transport uses energy in the form of ATP to move molecules across a selectively permeable membrane against the concentration gradient using protein pumps

Why do this

Protein pumps

What happens

Examples

Stephen Taylor httpsciencevideoswordpresscom

Active transport uses energy in the form of ATP to move molecules across a selectively permeable membrane against the concentration gradient using protein pumps

Why do this

Protein pumps

What happens

Examples

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Annotate this diagram to explain vesicle transport amp exocytosis

Animated tutorial httpbcswhfreemancomthelifewire8econtentcat_0400504003html

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Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

Stephen Taylor httpsciencevideoswordpresscom

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