Membrane Transporters (Wright)

Question 1

Three types of facilitated transport

Answer 1

1) Uniporter (GLUT1)
2) Co-transporter/Symporter (Na/glucose SLC5A1)
3) Exchanger (Cl/HCO₃ SLC4A3)

Question 2

Three classes of membrane transporters

Answer 2

1) Channels (Aquaporins)
2) Carriers
3) Pumps (Na/K; H/K)

Question 3

GLUT1, 2, 3, 4 locations

Answer 3

GLUT1 = BBB

GLUT2 = liver, intestine, kidney

GLUT3 = neurons

GLUT4 = muscle, fat

Question 4

Transcellular

Answer 4

Ion or molecule enters cell through plasma membrane, diffuses through cell, and exits on the other side

Question 5

Paracellular

Answer 5

Ion or molecule passes between cells through tight junctions

Question 6

“Leaky epithelia”

Answer 6

The tight junctions in leaky epithelia allow some ions to go through (but can be selective about which ones)

Note: water does NOT use paracellular pathway, it uses transcellular and aquaporins

Question 7

How is ATP generated in the mitochondria?

Answer 7

ATP synthetase/F0F1/ComplexV of electron transport chain

1) Complexes I, III, IV of electron transport chain generate H+ gradient from NADH and FADH2 from citric acid cycle
2) F0 subunit: H+ goes into one C subunit then hops 12 times, turning protein (including F1 alpha and beta subunits)
3) ATP binds to alpha/beta site and P+ADP binds to another empty site
4) Rotation of protein causes ADP+P to turn into ATP and causes initial ATP to come off into mitochondrial matrix