Week 6 Bollough Lecture 10

Question 1

why are channels not suitable for active transport?

Answer 1

Channels are not specific enough for certain molecules, wastes energy

Question 2

why is energy required to transport substances against their electrochemical gradient?

Answer 2

It is unfavourable to push molecules against their electrochemical gradient because molecules want to be in an equilibrium (not concentrated in cell, in this case), so to avoid this, we use energy to avoid this equilibrium state.

Question 3

What are the different transport processes?

Answer 3

2 types

a) Passive transport
i) Facilitated diffusion
b) Active transport
i) Primary active transporters: use direct source of energy e.g. a uniporter
ii) Secondary active transporters: couple the movement of one molecule to another e.g. symporter and antiporter

Question 4

Which is faster, pumps or channels?

Answer 4

Channels are usually faster with 10^7 ions per sec while pumps are at 10^3 ions per sec

Question 5

What is the structure of membrane pumps?

Answer 5

Requirements;

a) An interior cavity through the membrane
b) Protein needs to assume 2 configurations; for alternating access
i) Binding site as different affinities need to have different affinities

Question 6

why is active transport usually slower than passive transport?

Answer 6

Because…

a) Needs more than 1 molecule to transport
i) Takes more time to find molecules
b) More specific molecules
c) Needs energy