CP 2

Question 1

What is the difference between channel and carrier mediated transport?

Answer 1

• Channel: no binding/direct interaction, fast

- Carrier: binds, slower

Question 2

What is the difference between primary and secondary active transport?

Answer 2

• PAT: Uses ATP for transport to establish gradient

- SAT: Uses gradient from PAT for transport

Question 3

What is non-mediated transport?

What molecules can do this?

Answer 3

• Can diffuse through membrane without transport protein

- Nonpolar hydrophobic molecules (O2, CO2, N, fatty acids, small molecules, fat-soluble vitamins, etc.)

Question 4

What is active transport?

Answer 4

• Uses energy to drive substances AGAINST conc/electrochemical gradient
• Primary/secondary

Question 5

What is passive transport?

Answer 5

Moves substances DOWN conc/electrochemical gradient (using only their kinetic energy)

Question 6

What are the properties of ion channels? (5)

Answer 6

• Channel forms water filled pore that shields ions from hydrophobic core
• Ions do not bind to pore (so transport is RAPID)
• Amino acids lining pore determine selectivity
• Channel can harness energy STORED IN ION GRADIENTS
• Can be gated/non-gated

Question 7

In a gated ion channel, gates control open/close of pore, what stimuli control this?

Answer 7

Voltage, ligand binding, cell volume, pH, phosphorylation

Question 8

How is electrical current generated in ion channels?

How is this measured?

Answer 8

• Diffusion through channel generates current

- Current can be recorded by patch clamp (fluctuations represent opening/closing of channels)

Question 9

How does carrier mediated transport occur?
Why is it slow?
(3)

Answer 9

• Binds to protein, carrier changes shape for molecule to enter and pass
• Slow due to specificity, competition, saturation
• Can be passive or active

Question 10

What is primary active transport? (3)

Answer 10

• Energy directly derived from ATP hydrolysis to create gradient
• A typical cell uses 30% of its ATP energy on primary active transport
• Eg. Na/K ATPase

Question 11

What is secondary active transport?

Answer 11

• Energy stored in ionic conc gradient (from PAT) is used to drive the active transport of a molecule AGAINST its gradient
• Usually use Na gradient from Na/K ATPase in PAT

Question 12

What does the Sodium pump do?

Why is it important?

Answer 12

• Maintains low conc of Na and high conc of K in cytosol

- Difference in conc important for cell volume, RMP, contraction, SAT