Cell Membranes

Question 1

What are the components of a cell surface membrane and their functions?

Answer 1

Phospholipid bilayer- Controls the flow of small molecules in and out of the cell through its permeability

Carrier protein- Binds to large molecules and has its shape changed to transport the molecule across the membrane

Cholesterol- Controls the permeability of the membrane depending on how much there is

Channel protein- To transport polar substances across the membrane via attraction

Glycoprotein- Does cell signalling and helps maintain the structure of the cell

Question 2

What is the structure of a phosopholipid?

Answer 2

It has 2 hydrophobic tails that form the inside of a membrane and a hydrophilic head that forms the outside of a membrane

Question 3

What 3 factors affect membrane permeability and why?

Answer 3

1. Temperature-High temperatures will cause proteins to denature and lose shape allowing more molecules in, lower temperatures will freeze and break the phospholipids. E.g. upwards of 80˚C or downwards of 0˚C
2. Solvents-Will dissolve the lipids which causes more space for molecules to pass through and damages cell integrity. E.g. Organic ethanol
3. Detergents-Similar to solvents. E.g. Washing up liquid

Question 4

What is an integral protein?
Give an example of one and it’s function

Answer 4

A protein that spans the whole width of a cell.

Carrier/channel protein-Transport ions, sugars and amino acids across the cell membrane

Question 5

What is a peripheral protein?
Give and example of one and it’s function

Answer 5

A protein that is confined to either the inner or outer surface of a cell

Glycoprotein-Act as receptors on the extra cellular side(outside) and signallers on the cytosolic side(inside)