Cell Membranes

Question 1

What are all biological membranes composed out of

Answer 1

Proteins and lipids

Question 2

What do phospholipids do in the cell membrane (3 things)

Answer 2

1. Dictate the fluidity of the membrane
2. Allow lipid-soluble substances to enter and leave the cell
3. Prevent water-soluble substances entering and leaving the cell

Question 3

What is the job of protein channels in the cell membrane

Answer 3

Protein channels form water filled tubes which allow water-soluble ions to diffuse across the cell membrane

Question 4

What is the function of carrier proteins in the cell membrane

Answer 4

Carrier proteins bond to ions (like amino acids and glucose) and then change shape to allow the ions to move across the membrane

Question 5

What other two functions is there within cell membranes (other than protein channels and carrier proteins)

Answer 5

1. Act as receptors - for things like hormones

2. Form antigens for recognising cells

Question 6

What are the three functions of cholesterol in cell membranes

Answer 6

1. Reduce lateral movement of other structures like phospholipids
2. Make the membrane less fluid at high temperatures
3. Very hydrophobic so stops leakage of water from the cell

Question 7

What are glycolipids

Answer 7

Glycoproteins are made up of carbohydrate covalently bonded with a lipid

Question 8

What are the three functions of glycolipids in cell membranes

Answer 8

1. Act as recognition sites
2. Help mentain the stability of the membrane
3. Help cells to attach to each other to form tissue

Question 9

What are glycoproteins

Answer 9

Glycoproteins are carbohydrate chains that are attached to many extrinsic proteins on the outer surface of the cell membrane

Question 10

What are the two functions of glycoproteins

Answer 10

1. Act as recognition sites for hormones and neurotransmitters
2. Help cells to attach to each other and form tissue