Topic 2: Cells

Question 1

Suggest how APs become positioned across the membrane and make a channel through which ions can pass
- amino acids on one side of AP helix have hydrophobic properties
- the amino acids on the opposite of each helix have hydrophilic properties (2 marks)

Answer 1

1. hydrophobic side of AP next to fatty acids
2. as hydrophobic side of AP next to hydrophobic part pf phospholipid bilayer
3. hydrophilic sides allow ion movement through membrane
4. hydrophilic side form a channel

Question 2

Scientists observed these APs on prokaryotes using a TEM. they stained the APs using a monoclonal antibody with gold attached to it. suggest how these techniques allowed observation of APs on prokaryotes (3 marks)

Answer 2

1. antibody binds to AP
2. gold only present where AP located
3. antibody tertiary structure complemntary to AP
4. gold interacts with electrons
5. TEM used as high resolution

Question 3

Why did the students soak root tips in hydrochloric acid to observe mitosis

Answer 3

To breakdown cell walls and inhibit mitosis occurring

Question 4

Pressing the coverslip downwards enabled the student to observe the stages of mitosis clearly

Answer 4

To create a thin layer of cells so light can pass through

Question 5

Suggest and explain one reason why bacteria might not be able to produce every human protein

Answer 5

Do not have Golgi apparatus so can’t process package and modify proteins