Mass Transfer Lecture 9/28/22

Question 1

Define mass transfer?

Answer 1

Is a net movement of “mass” from one location to another in response to applied driving forces

Question 2

What is ADME?

Answer 2

Absorption, distribution, metabolism, and excretion

Question 3

What is dissolution?

Answer 3

Individual particles dissolved in the body

Question 4

After undergoing dissolution, the drug is in gastrointestinal fluids in solution form ready to permeate biological membrane, leading to its (blank)?

Answer 4

Absorption

Question 5

Diffusion step?

Answer 5

The drugs diffusion through the aqueous medium that bathes the membrane

Question 6

Partitioning step?

Answer 6

Passage of the drug molecules from the aqueous medium of the gastrointestinal fluids into the lipid bilayer of the membrane

Question 7

(Blank) is the molecular diffusion of the drug through relatively nonporous media

Answer 7

Drug permeation (transfer)

Question 8

Drug permeation across the biological membrane primarily depends on:

Answer 8

1. Drug partitioning
2. The structural nature of biological membrane (both its biochemical compositions and its thickness)
3. The nature of diffusion layer (the gastrointestinal content)

Question 9

(Blank) is the ability of the drug to distribute in a mixture of aqueous (polar) and lipid (nonpolar) system.

Answer 9

Drug partitioning

Question 10

If the drug is hydrophilic, the majority of the drug remains in what?

Answer 10

Water; but a trace of the drug is in the lipophilic part in order to maintain equilibrium

Question 11

What is the distribution coefficient or partition coefficient of the drug, which is constant to a drug?

Answer 11

Kd

Question 12

The logarithm of the partition coefficient (Log P) measures what

Answer 12

Lipophilicity (lipid solubility) of the drug

Question 13

Lipophilicity is important physiochemical property of drug as it affects:

Answer 13

-aqueous solubility (polarity) decreases with increased Log P value
-permeability increases with increase in Log P value

Question 14

Drug partitioning across biological membrane has been evaluated using the mixture of (blank) and (blank)

Answer 14

Octanol (representing the lipid, nonpolar system )
And
Water (representing the polar system)

Question 15

Most therapeutic agents exist as either weakly (blank) or (blank) in nature

Answer 15

Acidic or basic

Question 16

Aqueous solubility of a weekly acidic or basic drug, depends on the drugs (blank)

Answer 16

Dissociation constant (pKa) and the pH of the solution

Question 17

The (blank) states of a drug exhibit greater aqueous solubility than the (blank) states

Answer 17

Ionized
Unionized

Question 18

Mainly weekly acidic and basic drugs are subjected to ionization in the gastrointestinal tract. Therefore, there solubility dissolution and permeation are influenced by

Answer 18

The pH of the surrounding fluid

Question 19

Basic drugs are dissolved Better in what kind of environment

Answer 19

Acidic environment

Question 20

Acidic drugs are dissolved better in what kind of environment

Answer 20

Basic environment

Question 21

Basic are absorbed better in what kind of environment

Answer 21

Basic environment

Question 22

Acidic are absorbed better in what kind of environment

Answer 22

Acidic environment

Question 23

Most weekly acidic drugs are predominantly present in what

Answer 23

In their unionized or nonpolar forms at lower acidic pH of the gastric fluid, which favors their permeation from the stomach, as well as from the upper part Duodenum of the intestine. But some very weekly acidic drugs who’s PKA values are greater than eight remain in an unionized form at all pH values Which favors their faster passage across biological membrane

Question 24

Most weekly basic drugs are poly absorbed in the stomach because

Answer 24

They exist, largely in the ionized or polar states at pH 1-3. But weekly basic drugs with PKA values less than four remain Unionized through the intestine that favors there permeation

Question 25

Review on biochemical composition of the membrane:

Answer 25

Polar heads and nonpolar tails
Biological membranes act as lipid barriers, and the lipophilic or nonpolar Nature of drug molecules is important.

Question 26

Transfer mechanisms across membrane:

Answer 26

Passive diffusion (MW in range 100-400)
Pore transport (MW less than 100)
Carrier mediated
Ion pair transport (charged) (ionized)
Endocytosis (macromolecules)

Question 27

What is the most common process for passage of drugs through biological membranes?

Answer 27

Passive diffusion

Question 28

Passive diffusion is driven by the concentration gradient of

Answer 28

Drug across a membrane

Question 29

Do drug molecules bound to other structural materials, such as proteins, tissues, participate in diffusion process ?

Answer 29

No
Governed by Ficks Law

Question 30

When bound concentration decreases, unbound

Answer 30

Unbound is available for transfer now

Question 31

Increase in thickness of membrane , (blank) absorption

Answer 31

Slower
(Note: all other parts of Ficks Law have a ( increase , increase in absorption relationship)

Question 32

What is transcellular transport

Answer 32

Drugs diffuse through the matrix or core of the membrane. Constant across different tissues membranes. Depends on lipophilicity, polarity, and molecular weight of drug molecule.

Question 33

What is paracellular transport?

Answer 33

Drugs diffuse through the water field gaps between adjacent cells. Very from tissue to tissue. Depends on size of the junction and size of drug molecule. (Has to be small in size to squeeze between cells)

Question 34

Some polar compounds cross biological membrane faster than non-polar compounds through

Answer 34

Specialized carriers / transporters

Question 35

What are the two carrier mediated transport systems?

Answer 35

Facilitated diffusion and active transport

Question 36

What is facilitated diffusion?

Answer 36

It is less important, and is due to specific nature of this transport system, because drugs are specific to the body

Question 37

What is active transport?

Answer 37

More important and goes against a concentration gradient and utilizes ATP and energy drives the movement

Question 38

Transporters are proteins that reside on biological membranes and serve to facilitate the passage of chemicals into or out of a cell.

Question 39

What are the two broad classes of transporters?

Answer 39

Influx, transporters, and efflux transporters

Question 40

What are influx transporters?(uptake)

Answer 40

Transport drugs into the tissue or cell, and is most common. Organic anionic transport proteins are examples.

Question 41

What are Efflux transporters?

Answer 41

Transport drugs out of the cell or tissue. P-glycoprotein and MDR1 are examples.

Question 42

What is pore transport?

Answer 42

The aqueous channels which exist in cell membranes, allow very small, hydrophilic molecules, such as your rear water and low molecular weight sugars to be transported into the cells. However, because of the limited pore size, this pathway is of minor importance for drug absorption.

Question 43

What are the two types of endocytosis?

Answer 43

Pinocytosis and phagocytosis

Question 44

What is pinocytosis?

Answer 44

Cell drinking and occurs when dissolved solute are internalize through binding to nonspecific or specific membrane receptors

Question 45

What is phagocytosis?

Answer 45

Cell eating, and occurs when a particulate matter is taken inside a cell