Topic 2B - Cell membranes

What are cell membranes and what do they do?

Fluid mosaic structure

Phospholipid’s role in the fluid mosaic

Cholestrol’s role in fluid mosaic

Membrane permeability

The permeability of a membrane can be influenced by various factors, such as temperature and solvent concentration. This affects how much is allowed in/out the membrane.

Experiment: How temperature affects beetroot membrane permeability

Temperature’s affect on membrane permeability generally

Simple diffusion

Concentration gradient

The path from an area of high concentration to low concentration, the particles move down a concentration gradient.

Facilitated diffusion

Facilitated diffusion through carrier proteins

Facilitated diffusion through channel proteins

Factors affecting rate of simple diffusion

Factors affecting rate of facilitated diffusion

Osmosis

Water potential

Factors affecting rate of osmosis

How to make serial dilutions

How to make solutions at different concentrations using scaling factor

Scale factor = known concentration/desired concentration. E.g. if the answer is 2.5, we know it needs to be 2.5x weaker, so we would calculate desired volume/scale factor

Experiment: Using solutions to find out the water potential of potatoes

Active transport

from low to high concentration*

Carrier proteins in active transport

Distinctions between active transport and diffusion

Co-transporters

Factors affecting rate of active transport

Glucose absorption into the bloodstream via co-transport