What Happens at Cell Membranes

Question 1

Phospholipids are amphipathic - what does this mean?

Answer 1

They have a dual affinity, given they possess a hydrophillic polar head group and hydrophobic non polar tail

Question 2

What can and can’t pass through a phospholipid bilayer?

Answer 2

Lipid soluble / small molecules can pass through by diffusion

Ions and large polar molecules, water soluble drugs and hormones cannot pass through and hence would have to by transport proteins

Question 3

Describe simple passive diffusion

Answer 3

No transport proteins or ATP is utilised. Movement is down a concentration gradient, and is proportional to the extent of the gradient and hydrophobicity

Question 4

Facilitated passive diffusion is carried by two types of transporters. What are they called? Does it require energy?

Answer 4

Channel mediated
Carrier mediated

Does not need energy

Question 5

What does a uniporter do?

Answer 5

Moves one molecule at a time down a concentration gradient

Question 6

What does a symporter / antiporter do?

Answer 6

Couple movement of one or more ions down their concentration gradient with movement of another ion against its concentration gradient

Question 7

The intestinal cells uptake glucose in a special way. Describe it

Answer 7

Intestinal cells have a special glucose carrier SGLT1 which is driven by Na+ to move glucose into intestinal cells at low glucose concentrations

Question 8

The Na+/K+ ATPase moves what ions?

Answer 8

3 Na+ out

2 K+ in