Cell membrane

Question 0

Forces that drive diffusion

Answer 0

osmotic pressure, partial pressures, concentration, charge

Question 1

Reflection Coeff.

Answer 1

1=impermeable, 0= totally permeable

Question 2

tonicity

Answer 2

indicates effect of osmolarity of a solution on cell volume

Question 3

hypertonic solution

Answer 3

causes contracted cell volume

Question 4

hypotonic solution

Answer 4

causes expansion of cell volume

Question 5

normal plasma osmolarity

Answer 5

280 mOsmol/L water

Question 6

3 types of gated channels

Answer 6

ligand, ion, stretch

Question 7

3 types of carrier-mediated transport

Answer 7

facilitated diffusion, coupled carrier transport (secondary active, co- & counter), active transport

Question 8

example of ion channel mechanism important for cardiac muscle contraction?

Answer 8

Ca-Na exchanger allows Na influx which triggers Ca-dependent Ca release from SR in cardiac cell -> contraction

Question 9

Hyperkalemia

Answer 9

high potassium=acidosis

Question 10

the 4 mechanisms of transport

Answer 10

channel (passive), active transport, coupled carrier, facilitated diffusion (gated)

Question 11

example of facilitated diffusion

Answer 11

GLUT-4 transporter for glucose: it must bind glucose outside the cell before it opens (but only if conc. gradient drives!)

Question 12

What ion is commonly used to drive coupled carrier counter-transporters?

Answer 12

Na+

Question 13

How does one tell a facilitated diffusion transporter from a coupled carrier transporter?

Answer 13

the coupled carrier transporter will reach a saturation maximum rate (flux)

Question 14

3 characteristics of binding specificity in receptors

Answer 14

their ligands may be agonists/antagonists, they may bind more than one ligand, they are differentially expressed in individuals

Question 15

first messenger

Answer 15

extracellular signal

-fat or water-soluble classifications

Question 16

Kd

Answer 16

the ligand concentration where 50% of all receptors are bound.
higher Kd= lower receptor affinity for that ligand

Question 17

what determines effectiveness of competitive inhibition

Answer 17

ligand concentration

Question 18

competitive inhibitors act to…

Answer 18

reduce or increase (competitive excitation) the response of a ligand

Question 19

are competitive inhibitors more or less potent drugs

Answer 19

they are less potent than non-competitive inhibitors- because they disallow the original binding partner from interacting with the receptor regardless of the ligand concentration increase by the body

Question 20

describe equilibrium potential of a membrane

Answer 20

the net movement of ions is zero. If the gradient is bidirectional, the number of ions moving by concentration gradient equals the number moving by electrical/ voltage gradient

Question 21

Nernst potential meaning

Answer 21

the equilibrium potential of a certain ion; what the resting potential would be if only that ion existed; based on outside over inside concentration of CATIONS

Question 22

which 3 ions most significantly affect the resting membrane potential

Answer 22

Na, K, Cl

Question 23

Goldman-Hodgkin-Katz (GHK) Equation

Answer 23

predicts the resting membrane potential (based on relative permeability * outside/inside concentration for CATIONS, reverse for anions)

Question 24

Why is the resting membrane potential closer to that of K than Na

Answer 24

because the membrane is significantly more permeable to K (3 K in, 2 Na out via ATPase, and leak K channels)

Question 25

Why should we never worry about our membrane potential getting disrupted

Answer 25

because ATPase is in excess in all cells of the body

Question 26

what are the two ways by which the membrane capacitor does work

Answer 26

graded potentials and action potentials

Question 27

why does Na channel opening lead to depolarizations

Answer 27

because ENa (equilib potential) is more positive than Vm (voltage potential)

Question 28

Steady state potentials vs. equilibrium potentials

Answer 28

steady state pot.-when the current through the membrane is 0, the voltage is the constant (resting membrane potential) equilibrium pot. -the electrical potential that balances concentration gradient energy

Question 29

what does it mean that graded potentials are conducted DECREMENTALLY

Answer 29

the degree of polarization is dependent on how close one takes the potential measurement relative to the stimulus site

Question 30

in what type of inhibitor can the ligand concentration overcome the inhibition

Answer 30

competitive

Question 31

do inhibitors affect affinity of a ligand for its receptor

Answer 31

yes

Question 32

what type of inhibitor binds at a site other than the ligand-binding site

Answer 32

non-competitive inhibitor

Question 33

two cellular locations for steroid hormone receptors

Answer 33

cytoplasm, intra-nuclear

Question 34

the 4 mechanisms for receiving water-soluble first messengers

Answer 34

ion channels, tyrosine kinase, g-protein, janus kinase

Question 35

JAK kinase examples

Answer 35

cytokines (interleukins, interferons)

Question 36

adenylyl cyclase cascade

Answer 36

effector plasma membrane receptor downstream of a G-protein-coupled receptor. response requires [Ca ++ ] intracellular via intracellular release or IP3, activates PKA (ex: beta-adrenergic receptor for ephinephrine)

Question 37

IP3 cascade

Answer 37

G-protein-coupled receptor activates phospholipase C, makes IP3, activates PKC with diacylglycerol (DAG), Ca++ ER release

Question 38

absolute refractory potential

Answer 38

The time it takes for the action potential to exclude a subsequent action potential - no matter the stimulus strength

Question 39

relative refractory period

Answer 39

about 2 times the absolute refractory period (~0- -10 V) can elicit another action potential if stimulus is great enough. Outward K must be overcome by inward Na of new stimulus.