Cell/Membrane

Question 1

Partition Coefficient

Answer 1

Measure of substances lipophilicity
= 1: substance equally able to exist as solute in water and oil
> 1: substance is lipophilic and can pass easily through membrane

Question 2

Permeability Coefficient

Answer 2

Degree to which a substance can pass through the membrane (directly through bilayer or through channel/transporter)
= 1: means max permeability
= 0: means no permeability

Question 3

Reflection Coefficient (σ)

Answer 3

How easily a substance can cross the membrane based on its reflection
1 - if substance is reflected by the barrier (doesn’t pass through) completely impermeable
0 - if substance is not reflected by the barrier (passes through) it is permeant

Question 4

Pore

Answer 4

“Non-gated” transmembrane protein channel that is always open

Question 5

Channel

Answer 5

“Gated” transmembrane protein that can open and close

Question 6

Transporter

Answer 6

Transmembrane protein that undergoes a conformational change and facilitates the transport of a ‘packet’ of substrate across the membrane

Question 7

Ligand-gated channel

Answer 7

Binding of a specific molecule to a binding site on the channel causes a conformational change that opens the channel; selectivity is conferred by charged aa’s (cations vs. anions) and size

E.g. P2X receptor

Question 8

Voltage-gated channels

Answer 8

A change in membrane potential moves charged molecules within the channel i.e. charged aa’s causing a conformational change in the channel opening it

E.g. Voltage gated Na+ channel

Question 9

Mechanosensitive channels

Answer 9

Stretch of the membrane may affect the channel conformation either opening or closing the channel

Question 10

Factors determining rate of transport

Answer 10

1. Saturation of transporters
2. Number of transporters
3. Conformational change
4. Gradient

Question 11

Facilitated Diffusion

Answer 11

Solute is moved across a membrane down its electrochemical gradient (no ATP req), carrier proteins required w/ specificity for substrate
- increase transporters = increased flux

Question 12

Active Transport

Answer 12

Carrier protein req ATP to move solute against its electrochemical gradient, and in turn can generate a voltage across the membrane

Question 13

Primary Active Transport

Answer 13

Protein is usually ATPase enzyme, hydrolysis of ATP by this protein (due to binding of solute) is driving force for moving the solute against its concentration gradient)

Question 14

Na+/K ATPase

Answer 14

3: 2 electrogenic - both Na+ and K+ are being pumped against their concentration gradient across the membrane
* always on basolateral side of a cell

Question 15

H+ ATPase

Answer 15

Generates voltage as it transports positive ions in one direction, movement of H+ ions into the stomach lumen

Question 16

Ca2+ ATPase

Answer 16

Movement of Ca2+ from the sarcophagi into the sarcoplasmic reticulum

Question 17

Secondary Active Transport

Answer 17

Na+ is used as the driving force to move another solute against its electrochemical gradient
E.g. - Na+/Glucose co-transporter

Question 18

Secondary Active Exchangers

Answer 18

Utilize the electrochemical gradient of one substrate to drive another substrate in the opposite direction and generally against its electrochemical gradient
E.g. - Na+/Ca2+ exchanger: uses energy from the inwardly directed Na+ electrochemical gradient to drive the movement of Ca2+ out of the cell against its electrochemical gradient

Question 19

Henry’s Law

Answer 19

Amount of gas that will dissolve into liquid is determined by the partial pressure and the solubility of the gas

Question 20

Dalton’s Law

Answer 20

Percentage of a gas within a gas mixtures is used to measure it’s contribution to the total pressure

Question 21

Osmolarity

Answer 21

Total concentration of ALL particles in a soln.

Question 22

Tonicity

Answer 22

Concentration of only the osmotically active particles, only impermeable particles contribute to tonicity and cause changes in cell volume
- tonicity of a soln. Describes the volume change of a cell at equilibrium

Question 23

Penetrating Solutes

Answer 23

Glucose, urea, glycerol

- Solutes will distribute to equilibrium

Question 24

Non-penetrating Solutes

Answer 24

Sucrose, NaCl, KCl

• water will move to dilute solutes
• ultimately non-penetrating solutes determine the tonicity of a soln.

Question 25

Isotonic

Answer 25

If, at equilibrium, it causes the cell to neither swell nor shrink
- non-penetrating solute concentrations on both sides of the cell membrane are equal

Question 26

Hypertonic

Answer 26

If solution causes the cell to shrink

- non-penetrating solute concentration outside the cell is higher than on the inside

Question 27

Hypotonic

Answer 27

If solutions causes the cell to swell

- non-penetrating solute concentration on the outside of the cell is lower than on the inside

Question 28

Nernst Potential

Answer 28

Measure of the electrical energy required to balance the chemical energy of anion and keep net flux = 0, depends on the magnitude of the chemical gradient for the ion (bigger gradient = bigger Nernst potential)

Question 29

Agonist

Answer 29

Drug that binds to and activates a receptor in a way that brings about an effect

Question 30

Antagonist

Answer 30

Inhibits the action of an agonist, but has no effect in the absence of the agonist

Question 31

Efficacy

Answer 31

Maximal effect a drug can produce (if low, can’t give enough of the drug to make it worth it)

Question 32

Potency

Answer 32

Measure of the concentration or amount of drug necessary to produce an effect of EC50 (50% effect of the drug)

Question 33

Drug selectivity

Answer 33

Selective if there is at least a 1-fold difference between its binding affinity for its first target (the target which mediates the therapeutic effects) vs the second target (which mediates adverse effects)
*the greater the difference the more selective the drug

Question 34

Drug Absorption

Answer 34

Transfer of a drug from its site of administration to the blood stream, for IV delivery absorption is complete

Question 35

Weak acid drug

Answer 35

Protonated form is more liposoluble form

Question 36

Weak base drug

Answer 36

Unprotonated form is the more liposoluble form

Question 37

CYP3A4

Answer 37

Isoform of p450 that accounts for 30% of CYP450 enzymes in the liver, metabolizes approx 50% of all drugs

Question 38

Local Anesthetics

Answer 38

Block voltage-gates Na+ channels, preventing action potential propagation and pain perception

Question 39

Benzodiazepines

Answer 39

Bind GABAa receptor, enhances the ability of GABA to open the Cl- channel, thereby hyperpolarizing the neuron

Question 40

ENa+ (equilibrium potential)

Answer 40

+65mV

Question 41

ECa2+ (equilibrium potential)

Answer 41

+120mV

Question 42

EK+ (equilibrium potential)

Answer 42

-85mV

Question 43

ECl- (equilibrium potential)

Answer 43

-85mV