L3 - Control of intracellular pH Flashcards Preview

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

Flashcards in L3 - Control of intracellular pH Deck (46)
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1

What scale is pH measure on

Logarithmic

2

Decrease in pH means

An increase in acidity

3

High pH

Low acidity
High alkalinity

4

Low pH

High acidity
Low alkalinity

5

pH =

-log[H+]

6

Why should we worry about a change in pH

Can have profound physiological effects

7

What compensation must be made when pH increase

Remove H+
Alkalinisation

8

What compensation must be made when pH decreases

Increase H+
Acidify

9

How can pH IC be measure

Two electrodes inserted containing a H+ sensitive resin
and difference measures

10

Graph of pH vs voltage

Linear with a negative gradient

11

Equation to calculate V

= (slope x pH) + offset

12

Equation to calculate pH from graph

(V - offset) / slope

13

How may flourescent indicators be used to measure intracellular pH

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

14

3 factors involved in pH IC regualtion

Buffering
Acid extrusion
Acid loading

15

What is a pH buffer

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

16

Buffer systems act to

Minimise pH changes

17

What is buffering power

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

18

What do buffers NOT prevent

Changes in pH
Merely acts to minimise the magnitude of the change

19

Can buffers reverse pH changes

No

20

COOH is a

Proton donor

21

NH2 (amino group) is a

Proton reciever

22

What does acid extrusion mean

Getting acid out of a cell

23

What transport protein is needed for acid extrusion

NHE
Sodium proton exchanger

24

What does acid extrusion rely on

The inward Na gradient created by the Na/K ATPase

25

Acid extrusion mechanism has a __________

Setpoint

26

Describe the acid extrusion set point

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

27

NHE can be _________ __________

Allosterically modified

28

Describe the allosteric modification of NHE

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

29

Properties of NHE

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

30

What drug inhibits NHE

Amiloride