ICPP 3

Question 1

What is a semi-permeable membrane?

Answer 1

A layer through which only allowed substances can pass

Question 2

What does passive transport rely on?

Answer 2

permeability and concentration gradient

Question 3

What important roles do transport processes play?

Answer 3

Maintaining ionic composition
Maintaining pH
Regulating cell volume
Ion gradients for excitability of nerve and muscle

Question 4

What are 2 examples of ligand gated ion channels, and the benefit of this transport?

Answer 4

1. nACh receptors, Na+ influx
2. ATP sensitive K+ channels , close when ATP binds.
   This mechanism is FAST.

Question 5

What does the movement of charged molecules (ion) depend on?

Answer 5

Concentration gradient AND electrochemical gradient.
Will follow concentration gradient first but if equal concentration, a positive ion will want to move to the negative side and vice versa.

Question 6

What is the difference between a primary active transporter and a secondary active transporter?

Answer 6

Both transporters require energy, however primary active transports utilise ATP directly, whereas secondary transporters use existing concentration gradients. E.g NCX uses Na+ gradient to move calcium.
PMCA= primary transporter, uses ATP hydrolysis.

Question 7

What is the free ion distrubution across the membrane of Ca2+,Na+,K+ and Cl-?

Answer 7

Calcium: EC = 1mM, IC= 100nM
Na+: EC = 140mM, IC=14mM
K+: EC=6mM, IC= 160mM
Cl-: EC= 120mM, IC= 4mM

Question 8

Give an example of a unitransporter.

Answer 8

PMCA.

Proton pump.

Question 9

What is the different between a symporter and an antiporter?

Answer 9

Both are mechanisms for cotransport.
Symporter moves both molecules the same way.
Antiporter moves molecules in opposite directions.

Question 10

What are the functions of the Na+K+ ATPase?

Answer 10

1. Forms cellular concentration gradient of Na+ and K+.

2. Drives secondary active transport.

Question 11

Give 2 examples of secondary active transport.

Answer 11

Na+/H+ exchanger

Na+ glucose symporter in SI

Question 12

Which calcium transporter has a high affinity but a low capacity?

Answer 12

PMCA

Question 13

Wich calcium transporter has a low affinity but a high capacity?

Answer 13

NCX

Question 14

Reversal of the NCX has a possible role in ____.

Answer 14

Ischaemia. K+/Na+ ATPase stops functioning due to no ATP, intracellular Na+ rises and reverses the NCX.

Question 15

What are 2 acid extruder transporters?

Answer 15

Na+/H+ exchanger
Cl-/HCo3- transporter
Both alkalinase the cell

Question 16

What is an example of a base extruder?

Answer 16

Cl-/HCO3- exchanger

Question 17

What is amiloride?

Answer 17

A potassium sparing diuretic which inhibits the Na+/H+ exchanger

Question 18

Transport of _______ is key in cell volume regulation.

Answer 18

Osmotically active ions

Question 19

What transporter moves glucose from the gut lumen to the epithelial cells?

Answer 19

SGLT-1-Na+ dependent glucose symport

Question 20

Once in the epithelial cell, how does glucose then move into the blood?

Answer 20

GLUT transporters (GLUT 2 here). Facilitated transport down its concentration gradient

Question 21

What ensures that there is always a low concentration of glucose?

Answer 21

Rapid conversion to Glucose - 6-phosphate on entering the cell by hexokinase in liver and glucokinase in other cells.

Question 22

How does insulin stimulate the rate of uptake of glucose into adipose tissue and skeletal muscle?

Answer 22

Recruits Glut-4 transporters from the internal vesicular membranes to the plasma membrane to increase the transport capacity.

Question 23

What is the MOA of fluoxetine?

Answer 23

Outward flow of K+ leads to uptake of serotonin through SERT in synaptic cleft.
Fluoxetine inhibits SERT.

Question 24

What is the structure of the Na+/K+ ATPase?

Answer 24

Alpha and beta subunit.
Beta subunit directs pump to the surface
Alpha subunit has binding sites

Question 25

Why is the Na+/K+ ATPase ‘p-type’?

Answer 25

It phosphorylates aspartate