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BMS242 Core Phys Pharm > L3 - Control of intracellular pH > Flashcards

L3 - Control of intracellular pH Flashcards

1
Q

What scale is pH measure on

A

Logarithmic

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2
Q

Decrease in pH means

A

An increase in acidity

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3
Q

High pH

A

Low acidity

High alkalinity

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4
Q

Low pH

A

High acidity

Low alkalinity

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5
Q

pH =

A

-log[H+]

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6
Q

Why should we worry about a change in pH

A

Can have profound physiological effects

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7
Q

What compensation must be made when pH increase

A

Remove H+

Alkalinisation

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8
Q

What compensation must be made when pH decreases

A

Increase H+

Acidify

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9
Q

How can pH IC be measure

A

Two electrodes inserted containing a H+ sensitive resin

and difference measures

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10
Q

Graph of pH vs voltage

A

Linear with a negative gradient

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11
Q

Equation to calculate V

A

= (slope x pH) + offset

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12
Q

Equation to calculate pH from graph

A

(V - offset) / slope

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13
Q

How may flourescent indicators be used to measure intracellular pH

A

Cells loaded with a lipid soluble, inactive form of the indicator
Indicator converted to active form inside of the cell
Indicator is excited with light of a specific wavelength and ammount of light emitted at the second wavelength is measured
FLOURESCENCE IS PROPORTIONAL TO THE INTRACELLULAR PH
Indicator is calibrated inside of the cell
Membrane permeablised with proton ionophore, pH of bath = ph IC

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14
Q

3 factors involved in pH IC regualtion

A

Buffering
Acid extrusion
Acid loading

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15
Q

What is a pH buffer

A

Any system which moderates the effect of an acid/alkali load by reversibly consuming or relaseing protons

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16
Q

Buffer systems act to

A

Minimise pH changes

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17
Q

What is buffering power

A

The ammount of a strong base that must be added to raise the pH by given ammount

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18
Q

What do buffers NOT prevent

A

Changes in pH

Merely acts to minimise the magnitude of the change

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19
Q

Can buffers reverse pH changes

A

No

20
Q

COOH is a

A

Proton donor

21
Q

NH2 (amino group) is a

A

Proton reciever

22
Q

What does acid extrusion mean

A

Getting acid out of a cell

23
Q

What transport protein is needed for acid extrusion

A

NHE

Sodium proton exchanger

24
Q

What does acid extrusion rely on

A

The inward Na gradient created by the Na/K ATPase

25
Q

Acid extrusion mechanism has a __________

A

Setpoint

26
Q

Describe the acid extrusion set point

A

When pH is more alkaline than the set point - mechanism is inactive
Activation is at an acidic pH

27
Q

NHE can be _________ __________

A

Allosterically modified

28
Q

Describe the allosteric modification of NHE

A

Protons other than the ones which are being transported bind to NHE causing a confromational change which increases the activity

29
Q

Properties of NHE

A

Has a housekeeping function
Found on the basolateral membrane of epithelial cells
12 TM domains

30
Q

What drug inhibits NHE

A

Amiloride

31
Q

What is acid loading

A

Taking acid into the cell - increasing ammount of acid in the cell

32
Q

What protein does acid loading rely on

A

Cl/Bicarbonate exchanger

33
Q

Describe the mechanism by which the Cl/Bicarbonate exchanger works

A

1 Cl in

1 bicarbonate out

34
Q

Describe the relationship between CO2 and bicarbonate

A

H2O + CO2 H2CO3 HCO3- + H+

35
Q

Why does removal of HCO3- lower the Ph

A

H+ left behind

36
Q

Is Cl/Bicarb exchanger sensitive to pH

A

Yes

37
Q

At what pH does Cl/Bicarb exchanger have a high activity

A

Alkaline (high) pH

38
Q

At what pH does Cl/Bicarb exchanger have a low activity

A

Acidic pH

39
Q

What subscript denotes acid extrusion

A

J_e

40
Q

What letters denote acid loading

A

J_l

41
Q

How many subtypes of AE protein

A

4

42
Q

What are all of the isoforms of AE inhibited by

A

Stilbene derivative drug (DIDS)

43
Q

What type of exchanger is the Cl/Bicarb exchanger

A

AE family of exchangers (anion exchanger)

44
Q

Does exchange of Cl and bicarbonate depend on Na

A

No it is independent of Na

45
Q

Where is AE1 found most

A

In the red blood cells and the kidney

46
Q

Describe the state of the cell when it is at its resting pH

A

JL = JE
Extrusion = loading
No net proton flux
Steady pH

BMS242 Core Phys Pharm (9 decks)

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