L1 - Physiology and Pharmacology

Question 1

Composition of the cell membrane

Answer 1

Lipids - 42%
Proteins – 55%
Carbohydrates – 3%

Question 2

Ions with higher concentrations outside the cell

Answer 2

Na, Ca, Cl

Question 3

Ions with higher concentrations inside the cell

Answer 3

K, PO4, protein

Question 4

What travels across cell membranes via diffusion?

Answer 4

Lipid soluble molecules

Oxygen and Carbon dioxide

Question 5

What travels across cell membranes via transport proteins?

Answer 5

Small molecules and ions

Either by carriers, pumps, channels

Question 6

What travels across cell membranes via endocytosis?

Answer 6

Large molecules

Question 7

Active transport

Answer 7

Used in absence or against electrochemical gradient
Low turnover of around <100 a second
Requires ATP hydrolysis

Question 8

Na/K ATPase

Answer 8

Ubiquitous
Tetramer – 2 alpha and 2 beta subunits
3Na out and 2K in - electrogenic
Maintains low intracellular Na (intracellular negative charge)

Question 9

Passive transport

Answer 9

Follows the electrochemical gradient

Can be through carriers or channels

Question 10

Carriers - Na/glucose cotransporter

Answer 10

Diffusion and electrodiffusion 
Can be secondary active 
Highly selective 
Saturation – rate of carrier mediated uptake plateaus as substrate concentration increases 
Turnover 102-103 ions/s

Question 11

Classification of carriers

Answer 11

Uniporter - glucose
Symporter – Na/glucose
Antiporter – Na/halogen

Question 12

Channels

Answer 12

Conductive – ions flow creating a current
Non-conductive – no ions flow so no current
High turnover of 106 to 108 ions per second

Question 13

Patch clamp technique

Answer 13

Used to measure ion flow through a channel on a membrane patch
Reference electrode and electrode which sits in solution in patch pipette
Each time a K channel opens around 3 pA produced
Allowed identification, regulation and physiological function

Question 14

3 ways ion channels can change

Answer 14

Membrane potential
Number of ion channels
Open probability

Question 15

I = N.PO.g.(Vm-Ei)

Answer 15

I – total current carried by population channels
N – number of channels
PO – open probability
G – constant
Vm-Ei – membrane and equilibrium potential

Question 16

K channel crystal structure

Answer 16

KcsA (bacterial K channel) - homologous to Kir mammalian family
Grew channel protein crystals
X-ray diffraction analysis

Question 17

Kir channel

Answer 17

2 transmembrane domains

Question 18

Ky channel

Answer 18

4 groups of 6 transmembrane domains

4th domain is active

Question 19

Ach receptor

Answer 19

4 transmembrane domains

Question 20

CFTR Cl- channel

Answer 20

12 transmembrane domains
R groups
2 nuclear binding domains