Membrane Transport II (Lecture 10)

Question 1

True or False: GLUT receptors undergo conformational changes while aquaporins do not.

Answer 1

True

Question 2

Protein-mediated transport is faster than simple diffusion, highly specific, and the transport rate is limited by the number of transporters (____) and transporter affinity (____) for the molecule/ion

Answer 2

Vmax, Km

Question 3

True or False: In ATP powered pumps, One or more bindings sites for ATP located on regions facing the inner lumen.

Answer 3

False, facing the cytosol

Question 4

What are the four classes of ATP-powered pumps

Answer 4

P-class
V-class
F-class
ABC superfamily

Question 5

______ and ______ class pumps mostly transport H+ only, no phosphoprotein intermediate

Answer 5

V and F

Question 6

______ pumps transport a wide array of substrates, including toxins, drugs, phospholipids, peptides, and proteins, into or out of the cell

Answer 6

ABC superfsmily

Question 7

______ pumps are found in vacuolar membranes in plants, yeast and other fungi.

Answer 7

V-class

Question 8

______ pumps are found in the inner mitochondrial membrane, bacterial plasma membrane and thylakoid membrane.

Answer 8

F-class

Question 9

______ pumps transfer amino acids, sugars and peptides.

Answer 9

ABC superfamily

Question 10

P-class pumps have ______ α subunits and ______ β subunits.

Answer 10

2,2

Question 11

True or False: P-class pumps are often involved with generating ion gradients across membranes (ie. Na+, K+, Ca2+)

Answer 11

True

Question 12

______ generally function to generate the low pH of plant vacuoles and of lysosomes and other acidic vesicles in animal cells by pumping protons from the cytosolic to the exoplasmic face of the membrane against a proton electrochemical gradient.

Answer 12

V-class pumps

Question 13

______ are reverse proton pumps, also called ATP synthases

Answer 13

F-class

Question 14

What does ABC stand for in pumps?

Answer 14

ATP-binding cassette

Question 15

ABC pumps have two transmembrane ______ domains; form passageway
for cargo to pass through the membrane and Two cytosolic ATP-binding ______ domains; bind and hydrolyze ATP

Answer 15

T, A

Question 16

True or False: Up to 50% of ATP produced by red blood cells is used for ion transport!

Answer 16

True

Question 17

What pump is the most expensive?

Answer 17

Na/K

Question 18

True or False: Ions spontaneously move through channels in the plasma membrane down their electrochemical gradients

Answer 18

True

Question 19

In skeletal muscle cells, Ca2+ ions are concentrated and stored in the ______.

Answer 19

Sarcoplasmic reticulum

Question 20

Ca2+ from the SR lumen into to the cytosol causes?

Answer 20

Muscle contraction

Question 21

______ pumps in the SR membrane pumps Ca2+ from the cytosol back into the lumen of the SR, thereby inducing muscle ______.

Answer 21

P-class, relaxation

Question 22

______ is a high-affinity Ca2+ binding protein bind large amounts of Ca2+, thus reducing the ‘free’ concentration

Answer 22

Calsequestrin

Question 23

______ Makes up more than 80% of integral membrane

protein in muscle SR membranes

Answer 23

P-class Ca2+ ATPase

Question 24

In the P-class Ca2+ ATPase, E1 states have the binding sites facing the \_\_\_\_\_\_
and E2 states have the binding sites facing the \_\_\_\_\_\_.

Answer 24

cytosol, exoplasmic face

Question 25

Phosphorylation of ______ causes a E1 to E2 conformational change in P-class Ca2+ ATPase.

Answer 25

Aspartate

Question 26

______ state has a high affinity for Ca2+ and ______ state has a low affinity for Ca2+.

Answer 26

E1, E2

Question 27

E1 high affinity state: ______ oxygen atoms surround Ca2+ ions in two high affinity sites between helices ______, ______, ______, and ______ inside the membrane.

Answer 27

7

4, 5, 6, 8

Question 28

P-class Na+/K+ ATPase moves ______ Na+ ions ______ of and ______ K+ ions ______ the cell per ATP molecule hydrolyzed

Answer 28

3 out, 2 into

Question 29

If Km < free concentration (in the cytoplasm or external environment, depending on
direction pump is facing), then ions will ______.

Answer 29

Bind

Question 30

All V-class only transport H+ ions to?

Answer 30

Acidify the

lumen of particular organelles

Question 31

WHat are the two ways V-Class H+ ATPases can address positive charge build up?

Answer 31

Let in an equal number of anions to balance the charge

Move an equal number of a different cation out of the
organelle lumen

Question 32

In ABC proteins, each transmembrane T domain has ______ membrane spanning alpha helices.

Answer 32

10

Question 33

In ABC proteins, the two cytosolic ATP (A) binding domains are involved in?

Answer 33

Binding and hydrolysis drive change in conformation of the T domains

Question 34

______ flips phosphatidylcholine from cytosolic to exoplasmic leaflet

Answer 34

ABCB4

Question 35

True or False: Greater fluorescence (less quenching) in the presence of ATP than in its absence – indicates ABCB4 has flipped some of the labeled phospholipid to the inside leaflet

Answer 35

True

Question 36

______ in the exocrine tissue transports Cl ions and cystic fibrosis occurs when protein is defective.

Answer 36

CFTR

Question 37

Is CFTR a pump? why or why not?

Answer 37

Its not, its a Cl channel but uses T and A domains, and uses ATP.

Question 38

True or False in ABC CFTR, channel opening is triggered by protein phosphorylation and by binding of ATP to the two A domains

Answer 38

True