2.2 - Transport Mechanisms

Question 1

– How drugs move across cell membrane

– Drug must be in aqueous solution EXCEPT Pinocytosis

Answer 1

Transport Mechanisms

Question 2

Transport Mechanisms

Answer 2

• Passive Diffusion
• Carrier-Mediated Transport
• Convective Transport
• Ion-Pair Transport
• Vesicular Transport

Question 3

– Dominant
– Slowest; NON ENERGY requiring
– ALONG the concentration gradient (DOWNHILL)
– Passage across cell membrane

Answer 3

Passive Diffusion

Question 4

Governing Principle of Passive Diffusion

Answer 4

Fick’d Law of Diffusion

Question 5

dQ/dt

Answer 5

Rate of diffusion

Question 6

D

Answer 6

Diffusion coefficient

Question 7

A

Answer 7

Surface area

Question 8

K

Answer 8

Partition coefficient

Question 9

(CGi - Cp)

Answer 9

– Concentration Gradient

– Difference in concentration between 2 immiscible phases

Question 10

h or l

Answer 10

– Length of the membrane

– Membrane thickness

Question 11

D x A x K. (Cgi - Cp)

Answer 11

DIRECTLY Proportional

Question 12

h

Answer 12

INVERSELY Proportional

Question 13

Factors Affectig Rate of Diffusion

Answer 13

• Surface Area (A)
• Concentration Gradient (Cgi - Cp)
• Membrane thickness (h or l)
• Diffusion Coefficient (D)

Question 14

Surface Area

Answer 14

⬆️A = ⬆️dQ/dt

Question 15

Concentration Gradient (Cgi - Cp)

Answer 15

⬆️(CGi - Cp) = ⬆️dQ/dt

Question 16

Membrane Thickness (h or l)

Answer 16

⬆️h = ⬇️dQ/dt

Question 17

– Propert of a drug in relation to property of the mebrane

– 2 determinants

Answer 17

Diffusion Coefficient

Question 18

2 determinants

Answer 18

• Particle Size

* Lipophilicity

Question 19

Particle Size

Answer 19

⬇️PS = ⬆️ A = ⬆️dQ/dt

Question 20

Lipophilicity

Answer 20

⬆️Lipophilicity = ⬆️dQ/dt

Question 21

2 Factors

Answer 21

• Degree of Dissociation/ Ionization

* Partition Coefficient (K)

Question 22

[HA] — LUNA

Answer 22

• Non-ionized
• Non-polar
• Lipophilic
A B S O R B E D

Question 23

H + A — WIPE

Answer 23

• Ionized
• Polar
• Hydrophilic
E X C R E T E D

Question 24

Ka — DossociatiobnRate Constant

Answer 24

⬆️Ka = ⬇️Lipo = ⬇️dQ/dt

Question 25

pKa — -log Ka

Answer 25

⬆️pKa = ⬇️Ka = ⬆️lipo = ⬆️dQ/dt

Question 26

Partition Coefficient | — Lipid-H2O coefficient

Answer 26

⬆️K = ⬆️Lipo = ⬆️dQ/dt

Question 27

Carrier-Mediated Transport

Answer 27

* Features/ Characteristics | * Examples

Question 28

Features/ Characteristics

Answer 28

* Specificity/ Selectivity * Subject to Inhibition, Competition, Antagonism * Saturable

Question 29

Carriers recognize specific molecules

Answer 29

Selectivity/ Specificty | - Ex: Amino Acid transportrers — Recognized L-dopa but not dopamine

Question 30

- Ex: A.A Transporters — A.A in food can compete with L-dopa for CNS Transport

Answer 30

Subject to Inhibition, Competition, Antagonism

Question 31

– Based on the presence of limited # of carriers | – Displays MICHAELIS-MENTEN Kinetics/ Saturation Kinetics/ Nonlinear Kinetics

Answer 31

Subject to Saturability

Question 32

Examples

Answer 32

* Active Transport | * Facilitated Diffusion

Question 33

– Energy requiring – AGAINST concentration gradient (UPHILL) – Fastest

Answer 33

Active Transport

Question 34

– Non-enwrgy requiring | – ALONG concentration gradient

Answer 34

Facilitated transport

Question 35

– Linear – Concentration INDEPENDENT – Rate of Accumulation = Rate of Elimination

Answer 35

First Order Kinetics

Question 36

– Non-linear – Concentration DEPENDENT – Saturable Kinetics – Michaelis-Menten Kinetics

Answer 36

Zero Order Kinetics

Question 37

– Movemement through water-filled PORES/GAP JUNCTIONS | – Only PARACELLULAR transport mechanisms

Answer 37

Convective Transport

Question 38

Properties of Convectie Transport

Answer 38

* Pore Size/ Diameter * Change of the Pore Lining * Movement is by SOLVENT drug * Movement is ALONG concentration gradient

Question 39

– 7-10 angstrom | – Allows movement of ions/ molecules with MW 150-400

Answer 39

Pore Size/ Diameter

Question 40

– Pure (+) or Pure (-) | – Allows movement of ions with charge OPPOSITE of the pure lining

Answer 40

Charge of the Pure Lining

Question 41

– Mesh of transport for large ions — large exogenous ions form a neutral complex with an endogenous oppositely charged ion – Ex: Quaternary Amines

Answer 41

Ion-Pair Transport

Question 42

Vesicular Transport

Answer 42

* Pinocytosis | * Phagocytosis

Question 43

``` – Cell EATING – Small molecules; liquids – Requirement: Micelle form – Surfactant: Bile Salts/ Bile Acids – Vesicle-Mediated – Requires energy – Ex: Griseofulvin, ADEL Vitamins ```

Answer 43

Pinocytosis

Question 44

– Cell DRINKING | – Large molecules

Answer 44

Phagocytosis