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Flashcards in Membrane Permeability/Pumps Deck (51):
1

What is a semi permeable membrane?

A layer through which only allowed substances can pass

2

What are examples of hydrophobic molecules? (4) How do they pass through the phospholipid bilayer?

CO2
O2
N2
Benzene

Passive diffusion

3

What are examples of small polar uncharged molecules? How do they pass through the phospholipid bilayer?

Water
Urea
Glycerol

Passive diffusion

4

What are examples of large uncharged polar molecules? Can they passively diffuse through the phospholipid bilayer?

Glucose
Sucrose

No

5

Can ions passively diffuse through the phospholipid bilayer?

No

6

Can glucose passively diffuse through a phospholipid bilayer?

Yes (but very slowly) so treated as if it cannot

7

What are permeability coefficients used for in calculations? What scale are they measured in?

To show how long it takes for a molecule to move a certain distance across a bilayer

Logarithmic

8

What two factors is passive transport across a membrane dependent on?

Permeability
Concentration gradient

9

Why are models that show membrane transport proteins as 'rotating' or 'flip-flop' thought to be wrong?

Would require too much energy (thermodynamically unlikely)

10

How do gated pores transport molecules across a membrane?

Molecule binds ---> conformational change ---> molecule released on the other side

(Ping pong transport)

11

What causes voltage gated ion channels to open during membrane depolarisation?

Movement of positive amino acids ---> change in conformation (open channel)

12

An active process will show a ____ value for deltaG

A passive process will show a ____ value for deltaG

+ve (active)

-ve (passive)

13

Where does the energy come from for active transport to take place?

Some cells spend nearly ___% of their ____ on active transport

Hydrolysis of ATP

50% of their ATP

14

By the action of which two types of proteins can molecules be carried across a membrane in facilitated diffusion?

Carrier proteins (gated pore model)
Channel proteins

15

Is facilitated diffusion active or passive? Is the movement of molecules by carrier proteins or channels faster?

Passive

Channel proteins are faster

16

What type of membrane protein does active transport use to transport molecules across a membrane?

Carrier proteins

17

What is the intracellular [K+] in mM

155mM

18

What is the intracellular [Na+] in mM

12mM

19

What is the intracellular [Cl-] in mM?

4.2mM

20

What is the extracellular [K+] in mM?

4mM

21

What is the extracellular [Na+] in mM?

145mM

22

What is the extracellular [Cl-] in mM?

123mM

23

What is uni-transport? What is an example of a uni-transport protein?

Where only one molecule is transported by the protein at a time

H+ pump

24

What is co-transport? What two types of co-transport exist? Give an example of a co-transporter protein?

When more than 1 type of ion/molecule are transported per reaction cycle

Anti port (moves two molecules in opposite directions)
Symport (moves two molecules in the same direction)

Na/K ATPase pump

25

What ions does the Na/K ATPase pump move?

3 Na+ out
2 K+ in

26

What type of ATPase is the Na/K ATPase pump? What does this mean?

P type ATPase

ATP phosphorylates aspartame and produces a phosphoenzyme intermediate

27

What is the structure of a Na/K ATPase pump?

Has an alpha and a beta sub unit

Alpha subunit = where phosphorylation and transport occurs
Beta sub unit = is gylosylated and directs/anchors the pump to the cell surface

28

What is responsible for the resting membrane potential? What allows this to occur?

The diffusion of K+ out of the cell through channels

Occurs due to high intracellular [K+] created by the Na/K ATPase pump

29

What is an example of a symport co-transporter protein?

Na+/glucose co transport in the small intestine and kidney

(2Na+ and 1 glucose molecule)

30

How does fluoxetine work at synapses?

Blocks the SERT (serotonin re-uptake channel)
Increasing the action of serotonin
Causes sticky blood as serotonin is taken up by platelets

31

The Na/K ATPase pump provides the Na+ for...

Absorption of Na+ in epithelia
Action of the NCX (control of calcium levels)
Action of the NHE (pH control)

32

High intracellular [Ca] is...

Toxic!

33

What is the difference between the intracellular and extracellular Calcium ion concentrations?

10,000 fold

34

What molecules are moved by the PMCA? How is it powered?

1 H+ in
1 Ca2+ out

Using ATP

35

Which molecules are moved by the NCX? How is it powered?

3Na in
1Ca out

Secondary active transport

36

What molecules are moved by the SERCA? How is it powered?

Ca in
H+ out

Using ATP

37

Why is the SERCA not a pump? What type of transporter is it?

It is not on the plasma membrane

Primary active transporter

38

What is the difference in capacity and affinity of NCX and PMCA?

The NCX has a low affinity, high capacity
The PMCA has a high affinity, low capacity

39

What does depolarisation do to the NCX?

Reverses it

40

What 2 transporters are acid extruders and help to control cell pH?

NHE
NBC (sodium bicarbonate cotransporter)

41

What transporter is a base extruder and helps control cell pH? Which ions are moved at this protein?

AE (anion exchanger)

HCO3- out
Cl- in

acidifies the cell

42

Which ions are moved at the NHE and NBC respectively?

H+ out, Na+ in

HCO3- in, Na+ in
H+ out, Cl- out

Alkalinises the cell

43

Which drug inhibits the NHE?

Amiloride

44

The exchangers/transporters that help control cell pH are also important in regulating...

Cell volume

45

Cell volume is regulated by the movement of osmotically active ions such as...

How many water molecules does each ion bring with it?

Na+, K+, Cl-

6

46

A shrinking cell will ___________ ions

Influx

47

A swelling cell will ________ ions

Extrude

48

Where are bicarbonate ions reabsorbed in the kidney?
What is it important in the body for?

The proximal tubule

Ph buffering

49

Where is Na+ reabsorbed in the kidneys?

Cortical collecting duct
Distal convoluted tubule
Thick ascending limb

50

Which transporter helps in the reabsorption of Na+ in the thick ascending limb?

NKCC2
Na/K dichloride cotransporter

51

What drugs can be used for people with mild hypertension? What transporter do they work on?

Loop diuretics (e.g furosemide)

Block NKCC2

Less sodium and therefore water reabsorbed