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Flashcards in Membrane Transport Deck (52):
1

Which membrane components make the plasma and intracellular membranes selectively permeable?

Lipids and proteins

2

What are the three types of molecules that can cross the membrane without assistance?

Lipophilic molecules, certain gases, and small polar uncharged (e.g. water)

3

Based on Flick's Law of Diffusion, what is membrane permeability dependent on?

surface area, concentration gradient, membrane thickness, and membrane permeability

4

Ion movement tends to be in the direction that ___ the electrical gradient.

lowers

5

What are the two main types of membrane proteins?

channel and transporter (carrier)

6

Channels are the main way ____ crosses into the cell.

water

7

Channels are a continuous path from the cytosol to the extracellular region. Are these gated or not?

Gated

8

What kinds of molecules go through channel proteins?

Ions, water, small hydrophilics

9

T/F. Channel proteins use facilitated diffusion to transfer molecules.

True.

10

Transport proteins bind with ____ specificity to their substrate, inducing a conformational change necessary to function.

high

11

Which is faster: channel or transporter?

channel

12

What are the four types of transport protein classes?

uniport, symport, antiport, and ATP powered pump

13

A uniporter transports ___ substrate from high to low concentration.

one

14

Does symport directly require ATP?

No. The movement of molecules does not require ATP. ATP is used to form a gradient.

15

Symport is also called _____ active transport.

secondary

16

In antiport, what direction are substrates being moved?

Can be moved with or against gradient

17

ATP powered pumps have built in _____ activity.

ATPase

18

T/F. Aquaporins can be continuously open or gated.

True

19

Are ion channels always open, gated, or both?

Can be both open always or gated

20

Leak channels are an example of ____ channels. These channels are always open and let ions leak ___.

ion, in

21

What are the three types of gated ion channels that open only with stimulus?

voltage gated, ligand gated (chem signal like hormone), and mechanical gated

22

Charge of ion, size, and amount of water in the selectivity shell all contribute to ___ ____ selectivity.

Ion channel

23

How is the hydration shell removed from ions entering an ion channel?

Carboxylic acid residues line selectivity pore

24

GLUT 3's low Km value makes it extremely valuable for ___ cells.

neural

25

What are two examples of cotransporters in the body?

1. SGLT-1 (Glc, sodium symport. Found in small intestines and kidneys. Secondary active transport)
2. Chloride, bicarbonate exchanger (antiport, increased carbon dioxide carrying capacity of RBC).

26

P class pumps are reversibly phosphorylated during transport. What is an example?

Sodium-Potassium pump.
Explanation: E1 conformation has high sodium affinity. ATP is cleaved and the alpha subunit is phosphorylated. E2 conformation. Low affinity for sodium now but high affinity for potassium. Potassium binds, dephosphorylation occurs, and the E1 conformation is returned.

27

What are two sodium potassium pump inhibitors?

Drogoxin and ouabain

28

V-class proton pumps move hydride ions from the cytosol to ______ ____. This lowers the ___.

intracellular organelle, pH

29

Where are F class proton pumps most commonly found?

plasma membrane of bacteria, mitochondria, and chloroplasts

30

Where do ABC transporters bind ATP?

ABC domain

31

When is ATP cleaved in ABC transporters?

When the substrate binds

32

T/F. ABC transporters can only be used to bring substrates in.

F.
Explanation: ABC transporters (e.g. ABCB1 or MDR1) can be used to remove toxic contents from cell. In MDR1, drug resistant cells in cancer patients remove the lipophilic drug from the cell.

33

Which of these transporters is essential in lowering the acidity of the lysosome?

V Class

34

Protons flow through this pump to form ATP.

ATP synthase (e.g. F class pump)

35

How does energy state affect membrane diffusion?

No effect. Membrane diffusion is passive and does not require energy.

36

How is digoxin used to treat heart failure?
A. Increase extracellular sodium
B. Increase extracellular potassium
C. Increase bicarbonate intracellularly
D. Decrease chloride intracellularly

B.
Explanation: by inhibiting Na+/K+ ATPase, will have increased K+ outside because this pump lets 3 Na+ out and 2K+ in (PUMPKIN, pumps K in!)

37

Which of these pumps do not undergo reversible phosphorylation during transport?
Na+/K+ ATPase
F class ATP synthase
V class
SGLT1

SGLT 1

38

Skeletal muscle and fat cells rely on this insulin sensitive glucose transporter

GLUT 4

39

Patients with Cystic fibrosis involves mutations in which type of channel?

ABC transporters

40

What type of transport mechanism is used to move glucose into intestinal cells from the intestinal lumen?

Secondary active transport via SGLT-1

41

What type of transport mechanism is used to move glucose from the intestinal cell to the interstitial fluid?

Facilitated diffusion via GLUT-2

42

What class of ATP-powered pumps is the Na+/K+-ATPase?

P class

43

What cannot cross the membrane?

Ions, sugars, and amino acids

44

Most channels are ______ and partake in _____ transport.

gated, facilitated

45

What cannot travel through an aquaporin?

charged molecules

46

What do monovalent cation channels allow to pass?

Cation with plus one charge

47

How does insulin control blood glucose levels with GLUT 4?

When insulin binds, GLUT 4 goes to outside of cell membrane, binds glc, transports it in. Without insulin on the surface, GLUT 4 goes back in and is kept in an endosome until needed.

48

Where is each one found:
1. GLUT 1
2. GLUT 2
3. GLUT 3
4. GLUT 4

1. RBCs (second lowest Kt)
2. Pancreatic beta cells and liver cells (fourth lowest)
3. Neurons (lowest Kt)
4. Muscle and fat cells

49

SGLT1 is found in....

small intestines and kidneys

50

How many sodiums transported per glucose in SGLT-1?

Two sodium per one glucose

51

What is phosphorylated in Na/K pump?

Asp

52

Most ABC transporters are ______ in eukaryotes.

exporters