S2

Question 1

Structure of aquaporin channel

Answer 1

They are made up of 4 units (tetrameric). Have 6 transmembrane alpha helix proteins. The inner cavity is narrow and lined with hydrophilic amino acids. At the centre of the channel are +ly charged residues to prevent movement of charged oons e.g protons.

Question 2

What is the driving force for net diffusion?

Answer 2

The concentration gradient across the membrane

Question 3

Intracellular and extracellular concentrations for
Sodium ions
Chloride ions
Calcium ions
Potassium ions

Answer 3

Na: intra- 12mM and extra-145mM
Cl: intra- 4.2mM and extra- 123mM
Ca: intra- 10-7mM (0.1microM) and extra- 1.5mM
K: intra-155mM and extra 4mM

Question 4

Intracellular and extracellular concentrations for

Sodium ions

Answer 4

Na: intra- 12mM and extra-145mM

Question 5

Intracellular and extracellular concentrations for

Chloride ions

Answer 5

Cl: intra- 4.2mM and extra- 123mM

Question 6

Intracellular and extracellular concentrations for

Calcium ions

Answer 6

Ca: intra- 10-7mM (0.1microM) and extra- 1.5mM

Question 7

Intracellular and extracellular concentrations for

Potassium ions

Answer 7

K: intra-155mM and extra 4mM

Question 8

Example of primary active transporter

Answer 8

PMCA- plasma membrane Ca2+ ATPase which transports Ca2+ out.

Question 9

What is PCMA also referred to as? And why?

Answer 9

Ca2+-Mg2+-ATPase because magnesium is needed for hydrolysis of ATP.