Lecture 6- ATP- dependent pumps and ion exchangers

Question 1

function of sodium pump (Na+/K+ ATPase)

Answer 1

• forms sodium and potassium gradient
• necessary for electrical excitability
• drives secondary active transport

Question 2

secondary ative transport

Answer 2

active transporters powered by the gradient created by another reactive transporter e.g. the Na pump when sodium powers other transporters

e.g. Na/H+ or Na/Ca2+ or Na/glucose or Na/amino acid symports

Question 3

sodium pump (Na+/K+ ATPase) also has roles in

Answer 3

o Control of pH
o Regulation of cell volume and calcium
o Absorption of Na in epithelia
o Nutrient uptake e.g. glucose from SA

Question 4

intracellular calcium is

Answer 4

very low (0.1 um)

Question 5

where is calcium high

Answer 5

in the ER/SR and extracellular environment (2mM)

- 10,000-20,000 fold difference across plasma membrane

Question 6

high intracelliular calcium is

Answer 6

toxic to cells

Question 7

why is high intracellular calcium toxic

Answer 7

preventing calcium phosphate from forming- ossification of tissues

and

can cause ischaemia

Question 8

cells signal by small changes in

Answer 8

intracellular calcium

Question 9

control of intracellular calcium

Answer 9

Na/Ca exchanger, PMCA andSERCA

Question 10

Na+/Ca2+ exchanger

Answer 10

secondary active transport

• powered by the sodium gradient created by the sodium pump (Na+/K+ ATPase)
• pumps calcium out of the cell

Question 11

PMCA stands for

Answer 11

plasma membrane Ca2+ ATPase

- exchanges calcium for H+

Question 12

SERCA stands for

Answer 12

Sarcoplasmic reticulum pump Ca2+ ATPase

- pumps calciums into intracellular stores e.g. the SR

Question 13

calcium uniporters

Answer 13

use electrical gradient to pump calcium into the mitochondria

Question 14

Control of calcium: primary active transport

Answer 14

• PMCA

- SERCA

Question 15

PMCA- affinity and capacity?

Answer 15

high affinity

low capacity- removes residual calcium

Question 16

SERCA - affinity and capacity?

Answer 16

high affinity

low capacity- removes residual calcium

Question 17

Secondary active transport

Answer 17

Na/Ca exchanger (NCX)

Question 18

NCX - affinity and capacity?

Answer 18

low affinity
high capacity
- removes most calcium

Question 19

mitochondrial calcium uniporters

Answer 19

operate at high calcium to buffer damaging calcium

Question 20

more detail on the sodium calcium exchanger (NCX)

Answer 20

• Secondary active transporter
• Exchanges 3 sodium’s for 1 calcium
• Membrane potential dependent

Question 21

when the membrane is polarised

Answer 21

 High calcium inside

 Low sodium inside

Question 22

when the membrane is depolarised

Answer 22

high sodium inside

low calcium inside

Question 23

NXC in ischaemia

Answer 23

• ATP depleted- sodium pump (Na+/K+ ATPase) inhibited
• Na+ accumulates
• Cell depolarised
• Causes sodium calcium exchange to reverse action
• Sodium comes in instead of out and calcium goes out the cell
• High Calcium conc is toxic

Question 24

ion channels can be used to control cell pH using

Answer 24

Acid and base extruders

Question 25

acid extruders - give example

Answer 25

attempt to increase the pH of the cell- alkalinises - Na+/H+ exchanger (NHE) - sodium bicarbonate exchanger (NBC)

Question 26

base extruders- give example

Answer 26

Attempts to decrease the pH of the cell- acidified | - Anion exchanger

Question 27

normal pH of cell

Answer 27

7.35-7.45

Question 28

cell volume regulation

Answer 28

no standard method for cell volume regulation- diff cell types use diff combinations of transporters to achieve the regulation they need

Question 29

water follows

Answer 29

ions

Question 30

high osmolarity

Answer 30

water will flow into cell

Question 31

low osmolarity

Answer 31

water will leave cell

Question 32

cell swelling will

Answer 32

extrude ions | e.g. potassium chloride co-transporter

Question 33

cell shrinking

Answer 33

influx ions | e.g. sodium-chloride co transporters