Week 5 - Membrane Transport - Drewes

Question 1

Key facts about Glut transporters 1-5:

Go!

Answer 1

Glut1 – everywhere – glucose/galactose
Glut 2 – Liver, intestine, kidney - used for uptake and efflux – Gluocse/Gal/Fruc
Glut3 – Neurons – gluc/galac
Glut 4 – fat and muscle – regulated by insulin – ONLY glucose
Glut5 – intestine and sperm – fructose metabolizing tissues – fructose!

Question 2

Compare primary versus secondary active transport.

Answer 2

Primary – uses ATP to move ion in or out

Secondary – uses ATP to establish a gradient that can then be used to power bringing in or putting out molecules/ions

Question 3

Postulate the mechanism for opening voltage-sensitive channels.

Answer 3

There are positively charged alpha helices that move toward the negatively charged side of the membrane when the membrane become depolarized. As they move up, they also move outward a little causing the channel to open

Question 4

15. Compare in molecular terms a Na+, K+, and Ca2+ channels.

Answer 4

Na and Ca : Very similar have, 4 distinct subunits that span the membrane 6 times each.

K : 4 separate proteins that each span the membrane 6 times come together to make the channel

Question 5

What mutation results in cycstic fibrosis?

Answer 5

Cystic fibrosis is caused by F508 deletion in one of the chloride channel’s Nucleotide Binding Domains.

Problems with Cl- channels don’t allow Cl to be reabsorbed from the sweat and Na follows it out making for very salty sweat. IT causes problems like very viscous mucus which causes respiratory problems and trouble with infections.

Question 6

How is Tangier’s Disease caused?

What problems are associated?

Answer 6

ABC transport defect in ABCA-1 results in Tangier’s Disease

Causes problems with cholesterol resulting in heart attacks early in life

Question 7

What does tetrodotoxin cause?

What about the molecular structure allows it to function this way?

Answer 7

tetrodotoxin is a compound that specifically blocks Na+ channels in nerve cell membranes

Its business end has a NH2+, which can bind like Na+ to make it a good inhibitor

Question 8

Define an ABC transporter (by its features) and the role of specific ABC transporters in drug resistance.

Answer 8

ATP-Binding Cassette (ABC) Transporters
Use ATP to push stuff against thier conc. gradient

Increased efflux in cancer cells can prevent drugs from affecting them.