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ICPP > Membrane Permeability/Pumps > Flashcards

Membrane Permeability/Pumps Flashcards

1
Q

What is a semi permeable membrane?

A

A layer through which only allowed substances can pass

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2
Q

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

A

CO2
O2
N2
Benzene

Passive diffusion

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3
Q

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

A

Water
Urea
Glycerol

Passive diffusion

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4
Q

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

A

Glucose
Sucrose

No

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5
Q

Can ions passively diffuse through the phospholipid bilayer?

A

No

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6
Q

Can glucose passively diffuse through a phospholipid bilayer?

A

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

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7
Q

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

A

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

Logarithmic

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8
Q

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

A

Permeability

Concentration gradient

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9
Q

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

A

Would require too much energy (thermodynamically unlikely)

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10
Q

How do gated pores transport molecules across a membrane?

A

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

(Ping pong transport)

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11
Q

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

A

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

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12
Q

An active process will show a ____ value for deltaG

A passive process will show a ____ value for deltaG

A

+ve (active)

-ve (passive)

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13
Q

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

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

A

Hydrolysis of ATP

50% of their ATP

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14
Q

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

A 
Carrier proteins (gated pore model)
Channel proteins
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15
Q

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

A

Passive

Channel proteins are faster

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16
Q

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

A

Carrier proteins

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17
Q

What is the intracellular [K+] in mM

A

155mM

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18
Q

What is the intracellular [Na+] in mM

A

12mM

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19
Q

What is the intracellular [Cl-] in mM?

A

4.2mM

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20
Q

What is the extracellular [K+] in mM?

A

4mM

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21
Q

What is the extracellular [Na+] in mM?

A

145mM

22
Q

What is the extracellular [Cl-] in mM?

A

123mM

23
Q

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

A

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

H+ pump

24
Q

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

A

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
Q

What ions does the Na/K ATPase pump move?

A

3 Na+ out

2 K+ in

26
Q

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

A

P type ATPase

ATP phosphorylates aspartame and produces a phosphoenzyme intermediate

27
Q

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

A

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
Q

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

A

The diffusion of K+ out of the cell through channels

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

29
Q

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

A

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

2Na+ and 1 glucose molecule

30
Q

How does fluoxetine work at synapses?

A

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

31
Q

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

A

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

32
Q

High intracellular [Ca] is…

A

Toxic!

33
Q

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

A

10,000 fold

34
Q

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

A

1 H+ in
1 Ca2+ out

Using ATP

35
Q

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

A

3Na in
1Ca out

Secondary active transport

36
Q

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

A

Ca in
H+ out

Using ATP

37
Q

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

A

It is not on the plasma membrane

Primary active transporter

38
Q

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

A

The NCX has a low affinity, high capacity

The PMCA has a high affinity, low capacity

39
Q

What does depolarisation do to the NCX?

A

Reverses it

40
Q

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

A

NHE

NBC (sodium bicarbonate cotransporter)

41
Q

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

A

AE (anion exchanger)

HCO3- out
Cl- in

acidifies the cell

42
Q

Which ions are moved at the NHE and NBC respectively?

A

H+ out, Na+ in

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

Alkalinises the cell

43
Q

Which drug inhibits the NHE?

A

Amiloride

44
Q

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

A

Cell volume

45
Q

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

How many water molecules does each ion bring with it?

A

Na+, K+, Cl-

6

46
Q

A shrinking cell will ___________ ions

A

Influx

47
Q

A swelling cell will ________ ions

A

Extrude

48
Q

Where are bicarbonate ions reabsorbed in the kidney?

What is it important in the body for?

A

The proximal tubule

Ph buffering

49
Q

Where is Na+ reabsorbed in the kidneys?

A

Cortical collecting duct
Distal convoluted tubule
Thick ascending limb

50
Q

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

A

NKCC2

Na/K dichloride cotransporter

51
Q

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

A

Loop diuretics (e.g furosemide)

Block NKCC2

Less sodium and therefore water reabsorbed

ICPP (8 decks)

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