cell membranes general

Question 1

1. What is the difference between the outer and inner surface of the plasma membrane?

Answer 1

1. The outer surface of the membrane has chains of sugar, carbs that are part of the glycolipids and glycoproteins

Question 2

2. Explain under what circumstances CO2 might diffuse into a palisade cell, how the process takes place?

Answer 2

2. -Photosynthesis in the palisade cell uses CO2 maintaining a low concentration inside the cell
   
   • The concentration of CO2 outside and in air spaces is higher than inside the cell
   • CO2 diffuses into cell down CG,

Cell wall and plasm and membrane are both permeable to CO2

Question 3

3. Suggest what might be moved out of a cells in the pancreas by exocytosis?

Answer 3

Digestive enzymes, insulin and glucagon

Question 4

4. Approximate width of membrane

Answer 4

7nm

Question 5

5. Function of the intrinsic channel protein

Answer 5

Create a water filled channel in which polar ions can pass through

Question 6

6. 5 roles of a glycoprotein

Answer 6

6. Cell adhesion to hold cells together
   
   • attach to water molecules to stabalise membrane
   • act as antigens
   • cell recognition, precise structure means they can distinguish self from non-self
   • transport substances up CG, using ATP (active transport)
   • create a water filled channel in which polar substances pass through

Question 7

7. How do small substances enter the PM

Answer 7

7. Simple diffusion, pass through temporary gaps formed by vibrating phospholipids, move down using their own motion of energy

Question 8

8. How do Charged, large substances enter the PM

Answer 8

8. Facilitated diffusion, channel/ carrier protein
   
   • if it’s a gated ion they bind with the protein to open it
   • or pass through water filled channel protein down CG
   • NO ATP

Question 9

How do substances enter via active transport

Answer 9

Transporter proteins required
Requires ATP energy
Atp changes the shape of the transporter proteins, 3 Na ions out, 2 K in