MB - Membrane Potentials

Question 1

function of plasma membrane

Answer 1

structural barrier
maintain different mixtures of substances in and out of cell 
fluidity of cell
communicate between cells
respond to external stimuli

Question 2

2 types of membrane proteins

Answer 2

integral/transmembrane

peripheral/extrinsic

Question 3

types of transport across membrane

Answer 3

diffusion
protein mediated membrane transport - channel or carrier proteins
endocytosis - phagocytosis, pinocytosis
exocytosis

Question 4

what kind of molecules are able to freely diffuse across cell membrane

Answer 4

lipid soluble
and small uncharged molecules
driven by concentration gradient

Question 5

what kind of molecules are NOT able to freely diffuse across cell membrane

Answer 5

charged ions
water soluble
hydrophobic interior

Question 6

what causes a membrane potential to appear

Answer 6

separation of opposite charges blocked by cell membrane because opposite charges attract

Question 7

positively charged ions

Answer 7

cations

Question 8

negatively charged ions

Answer 8

anions

Question 9

why is membrane potential of cells important?

Answer 9

electrical difference across membrane
excitable cells actively induce changes
basis for electrical excitability of nerve and muscle
harnessed for transporting substances

Question 10

how does the plasma membrane barrier establish membrane potential

Answer 10

acts as a barrier and establish differences in concentrations of key charged ions across PM

Question 11

Is the intracellular fluid more positive or negative than the extracellular fluid

Answer 11

Cell membrane is more negative inside than outside

Question 12

what causes the inside of the cell membrane to be more negative inside than outside

Answer 12

unequal distribution of K+, Na+ and A- between inside and outside of cell
selective leakiness of PM to K+
Electrical gradient: ATPase Na+/K+ - 3Na+ out and 2K+ in (makes inside more -ive)
negative charge on inside of cell drives K+ inside cell
Concentration gradient: Diffusion of K+ leaks out of cell down concentration gradient by pump - main reason why inside more -ive

Question 13

resting membrane potential

Answer 13

-70mV

Question 14

2 other membrane constituents responsible for making inner membrane potential negative

Answer 14

Phosphatidylinositol (PIP2)

Phosphatidylserine (PS)

Question 15

where is Na+ ions concentrated and why?

Answer 15

concentrated outside of the cell

would be driven to the inside of the cell but plasma membrane is not very permeable to Na+ - few leak channels

Question 16

why is K+ equilibrium potential important

Answer 16

resting membrane potential always close to K+ equilibrium potential If the membrane becomes permeable to another ion, it will ‘move toward’ its equilibrium potential
changing the membrane potential

Question 17

depolarisation

Answer 17

membrane potential becomes more positive

Question 18

hyperpolarisation

Answer 18

membrane potential becomes more negative

Question 19

repolarisation

Answer 19

restores the potential

Question 20

types of ion channels

Answer 20

leak channels - always stay opened
voltage -gated channel - usually closed but open when voltage changes
ligand gated channel - need to bind to neurotransmitter to be opened

Question 21

features of ion channels

Answer 21

integral membrane proteins
selectivity filter
gates
rectification

Question 22

different structure of pore in ion channels

Answer 22

tetra - K+ channel
pentamers with a common pore- ligand gated cation and anion
intracellular pore in each subunit - Cl- channels

Question 23

how does local anaesthetics work and name 2 examples

Answer 23

(inhibit voltage-gated sodium (Na+ channels, i.e. Xylocaine/Lidocaine)