Movement across membranes 1- Diffusion How to molecules move across phospholipid bilayer membranes? Starter: Explain how a fish in a sealed packet cannot be smelt, but open it and the room quickly smells like fish.

Success Criteria What is meant by passive transport ( diffusion and facilitated diffusion including the role of membrane proteins), active transport, endocytosis and exocytosis.

What is meant by passive transport ( diffusion and facilitated diffusion including the role of membrane proteins)

What do you know about diffusion?

Kinetic energy Goes both ways across a membrane. Equilibrium reached Down a concentration gradient It is passive Molecules never stop moving.

sWY

Diffusion The passive movement of molecules down a concentration gradient. Equilibrium A point reached where the concentration of a molecule is the same on both sides of a ppm.

Simple Diffusion

There are different types of carrier proteins in the membrane: ATP Channel proteinGated-channel proteinCarrier protein (passive) Carrier protein (active)

Fat-soluble diffuse down a concentration gradient. SOME water molecules can passively move – they are very small. Extracellular space Cytosoplasm (aqueous) Polar molecules Fat-soluble molecules diffuse down a concentration gradient. SOME water molecules can passively move – they are very small. Other small, non-charged molecules can diffuse through e.g. O 2 and CO 2

Facilitated diffusion – channel proteins Extracellular space Cytosoplasm (aqueous) Fat-soluble molecules and small molecules/ions diffuse through e.g. O 2 and CO 2 Polar molecules Large or charged molecules have to move through proteins. Some move through carrier proteins. These carrier proteins are channels that allow 1 shape through. Some are gated so can be closed/opened. This is still diffusion and passive. E.g. Na+ gates in nerve cells

What about charged or large molecules?

Facilitated Diffusion – a gated channel protein

There are different types of carrier proteins in the membrane: ATP Channel proteinGated-channel proteinCarrier protein (passive) Carrier protein (active) Carrier proteins have a specific shape that bind to a specific molecule. E.g. glucose/Aa The protein changed shape to allow the molecule through to the other side.. O 2 and CO 2

Task – complete this table Substance moved byExamples Simple diffusion Sodium and calcium ions Facilitated diffusion using carrier proteins.

What can affect the rate of diffusion? Use the text book page 23 to find out what affects the rate of diffusion and why.

Success criteria active transport, endocytosis and exocytosis.

Active transport Watch the animation on the next slide and explain how active transport works.

Active Transport Inside of cell Outside of cell ATP P ADP

Describe the role of active transport in across a cell membrane. Protein carrier Complementary Charged/large ATP Energy Faster Concentration gradient.

Where is active transport used? Active transport includes: Ca 2+ pumps in muscles Active reabsorption in nephrons Absorption of the products of digestion Sugar loading into phloem

One way

The protein involved in active transport has a specific shape. This shape changes as the protein moves through it, using ATP. This change in shape means the protein cannot travel the other way through the protein.

Endocytosis vs Exocytosis The clue is in the name! Other words parts – Phago – solid Pino – liquid. What would you call the movement of a liquid into a cell? What would you call the movement of a solid out of a cell?

Movement of bulk materials using ATP. E.g. Hormones WBC