Membrane potentials

Question 1

is the inside of the cell more positive or negative than the extracellular fluid?

Answer 1

inside of the cell is more negatively charged than outside of the cell -

Question 2

what pump maintains the resting membrane potential of a cell?

Answer 2

the sodium potassium pump maintains the resting membrane potential - pumping sodiuma dn potassium against their natural concentration scales

Question 3

what is the resting membrane potential voltage

Answer 3

-70mV

Question 4

describe the extracellular and intracellular composition of ions

Answer 4

SOKI

• sodium is greater outside of the cell than inside, K+ is greater inside of cell than outside
• there is a greater concentration of free Ca2+ outside of the cell b/c intracellular Ca2+ is bound to mitochondria
• greater concentration of free Mg2+ intracellularly than extracellular

Question 5

is the concentration of proteins greater outside or inside of the cell?

Answer 5

greater intracellularly

Question 6

is the concentration of glucose higher inside or outside of the cell?

Answer 6

it is much greater outside of the cell, because inside of the cell the concentration is very low

Question 7

is there a difference in osmolarity intracellulary/extracellulary?

Answer 7

no difference- both 290mosm

Question 8

what molecules freely diffuse across membrane?

Answer 8

O2, CO2, and lipid soluble moelcules

Question 9

describe the selective permeability (leakiness) of the plasma membrane?

Answer 9

• semi-permeable nature of biological membranes
• high permeability for K+ and low permeability for Na+ and Cl-

Question 10

describe votage gated ion channels

Answer 10

voltage sensor in ion channel protein - conformational change in response to changes in membrane potential opens or closes the channel

Question 11

what drugs act on voltage- gated ion channesl?

Answer 11

• local anaesthetics- inhibit voltage-gated Na+ channels
• antihypertensive agents -
• antiarrhythic drugs - inhibit voltage gated K+ or Na+ channels

Question 12

describe active transport

Answer 12

• requires ATP
• carrier-mediated transport

only open to one side at a time and can move cargo against the gradient

Question 13

describe the Na+ Ka+ and ATPase pump

Answer 13

establishes Na+ and K+ concentration gradients across plasma membrane using ATP - transports 3 Na+ out for 2K+ in (SOKI)

Question 14

what is the ‘rule of thumb’ for the ‘NERNST EQUATION’?

Answer 14

a 10 fold concentration gradient of a monovalent is balanced by a 60mV electrical potential difference