Lecture 8 - Membrane Protein Function Minus a level basics

Question 1

What do carrier proteins do

Answer 1

transport small solutes (ie glucose, amino acids) across membranes

Contain specific solute binding sites that cause conformations in the protein - gated

Question 2

What is symport

Answer 2

Transport of 2 different molecules in the same direction (eg a co-transported ion) (slide 6)

Question 3

What is antiport

Answer 3

Transport of 2 different molecules in the opposite direction (slide 6)

Question 4

What is an example of a symporter

Answer 4

Lactose permease (can transport a molecule against a concentration gradient with an ion with its concentration gradient)

Question 5

What is an example if an active transport symporter

Answer 5

Glucose sodium symporter

Question 6

Wha is an example of an antiporter

Answer 6

Na/K ATPase

Question 7

What are some sources of energy that drive pumps

Answer 7

eg. light

Question 8

What is a Patch Clamp

Answer 8

Small area of membrane (hopefully containing channel proteins is removed from a membrane and seals the end of a glass capillary to observe the channel protein

Question 9

Describe propogation in voltage gated cells

Answer 9

A stimulus that causes sufficient depolarisation of the plasma membrane causes voltage gated Na+ channels to open
Na+ enters the cell depolarises the membrane further causing more Na+ channels to open. This is self perpetuating
Channels then become inactivated or else the membrane would permanently be depolarised

Question 10

What happens at nerve terminals

Answer 10

When the action potential reaches nerve terminal voltage gated Ca2+ channels open

Ca2+ enters the cell

This causes fusion of vesicles with the plasma membrane and the release of neurotransmitters

Question 11

What heritable diseases can come from defects in ion channels

Answer 11

Cystic fibrosis caused by defects in a chloride channel

Leads to lung congestion and infections

Unclear why a defect in the channel leads to disease

Question 12

What are the types of cell surface receptors

Answer 12

Ion channel linked
G-protein linked
Enzyme linked

Question 13

Describe G-protein coupled receptors

Answer 13

7 transmembrane spanning receptors
C-elegans (worm) genome appears to have >1000 GPCR genes (5% of genome)
Estimates are that we (humans) have approx. 800 GPCRs
Huge potential as drug targets
More than a quarter of all prescription drugs bind to GPCRs