Exam 2 Diffusion

Question 1

A type of diffusion that is considered “free” (uncombined/combined)

Answer 1

Uncombined

Question 2

A type of diffusion with extracellular or cellular constituents (uncombined/combined)

Answer 2

Combined

Question 3

T or F: Diffusion occurs in a purely random fashion if the molecules are not charged and moving in an electrical gradient

Answer 3

True

Question 4

Transfer of most drugs across a biological membrane occurs by ______ diffusion from a region of higher activity to a region of lower activity

Answer 4

Passive diffusion

Question 5

Fick’s Law equation

Answer 5

(dM/dt) = (DA(c1 - c2)) / x

dM/dt = rate of diffusion
A = area of membrane
D = diffusion coefficient
c1 = concentration of donor side
c2 = concentration of receptor side
x = membrane thickness

Question 6

Permeability constant equation

Answer 6

P = D/x, cm/sec

Question 7

Unlike synthetic membranes, biological membranes are ____ (uniform/patchy)

Answer 7

Patchy

Question 8

P, D, and x are (absolute/mean) values of the whole membrane?

Answer 8

Mean values

Question 9

With time, c1 approaches c2 in a(n) (linear/exponential) mode

Answer 9

exponential (first order) mode

Question 10

When is equilibrium established in the concentration gradient?

Answer 10

When c1 = c2

Question 11

In almost all cases of oral drug administration, the (blood/GI) compartment functions as a “sink”

Answer 11

Blood

Question 12

Diffusion of (charged/uncharged) molecules is known as nonionic diffusion

Answer 12

Uncharged

Question 13

What does Brownian Motion measure?

Answer 13

Distance traveled by the molecule

Question 14

What type of particle is the Stokes-Einstein equation used for?

Answer 14

Spherical particles

Question 15

What is the radius in angstroms of sucrose?

Answer 15

4.4 A

Question 16

What is the radius in angstroms of albumin?

Answer 16

35 A

Question 17

What two factors determine the probability of an ionized drug penetrating a membrane?

Answer 17

1. Concentration (chemical) gradient

2. Potential difference (electrical gradient) across the membrane

Question 18

A biological membrane has which charge on the intracellular portion?

Answer 18

Negative

Question 19

A biological membrane has which charge on the outside?

Answer 19

Positive

Question 20

A cationic drug molecule is repelled by the positive charge on the outside of the membrane. Only molecules with (low/high) kinetic energy pass through the barrier

Answer 20

High kinetic energy

Question 21

Once a cation is inside the membrane, it is attracted by the (positive/negative) charged intracellular surface, and repelled by the (positive/negative) outer surface

Answer 21

negative; positive

Question 22

Since there is also a _____ difference across the membrane, the cation is also moving “downhill”

Answer 22

concentration difference

“downhill” means moving from higher to lower concentration

Question 23

If a molecule is moving downhill, then it is moving (with/against) the electrochemical gradient?

Answer 23

with the electrochemical gradient

Question 24

Why might a polyvalent cation never penetrate the membrane?

Answer 24

It will be greatly repelled by the outside of the membrane

Question 25

The type of movement of a substance through a biological membrane at rates much greater than would be anticipated based on the polarity of the solute and its molecular size

Answer 25

Facilitated diffusion

Question 26

In facilitated diffusion, particles move (uphill/downhill)

Answer 26

Downhill

Question 27

Facilitated diffusion relies on what type of molecule?

Answer 27

Carrier molecules

Question 28

T or F: Facilitated diffusion uses a drug-carrier complex that has a lower permeability than the drug alone

Answer 28

False: the drug-carrier complex has a greater permeability than the drug alone

Question 29

What can happen to the carrier complex after it crosses through the membrane?

Answer 29

The carrier is returned to the original side of the membrane to be reused or to be constantly produced and eliminated

Question 30

Transport of a substance through a biological membrane uphill against its electrochemical gradient; energy dependent

Answer 30

Active transport

Question 31

What type of transport involves the movement of some drugs across neuronal membranes?

Answer 31

Active transport bitches

Question 32

Pinocytosis is a type of ______ that is energy (independent/dependent) relatively (fast/slow) and (efficient/inefficient)

Answer 32

phagocytosis; energy dependent; slow; inefficient

Question 33

The creation of a pouch into a saccular structure in which extracellular material is trapped

Answer 33

Invagination

Question 34

Anti-inflammatory agents that significantly inhibit pinocytosis in macrophages and other cells involved in inflammation

Answer 34

Adrenal gluccocorticoids

Question 35

What is the diffusion route that involves dissolution in the membrane lipids, followed by diffusion to the far side of the membrane into the cytosol

Answer 35

Partitioning

Question 36

The presence of macromolecules (proteins) in the cytoplasm results in a colloidal preparation known as

Answer 36

Sol

Question 37

When traveling through pores, the ____ of the molecule must be smaller than the pore

Answer 37

Diameter

Question 38

How do water-soluble, lipid insoluble molecules pass through the membrane?

Answer 38

Pores.... rarely pinocytosis

Question 39

T or F: A drug with a low lipid solubility in the presence of a membrane carrier or active transport system can still penetrate through the membrane

Answer 39

True

Question 40

What is the major barrier for drugs with low lipid solubility when trying to pass through the membrane?

Answer 40

The interaction between the polar solute and water - it is difficult for the solute to leave water and enter the lipid

Question 41

T or F: Drugs with a high lipid solubility do not pass easily through the membrane

Answer 41

False; drugs with a high lipid solubility pass easily through the membrane

Question 42

The _____/_____ partition coefficient is more important than lipid solubility itself when determine which molecules will pass through the membrane

Answer 42

lipid/water partition coefficient

Question 43

T or F: A favorable partition coefficient sufficient for absorption to occur

Answer 43

False; there must be a significant concentration of the drug in water or extracellular fluid as well

Question 44

What two factors determine the partition coefficient of a drug?

Answer 44

1. Polarity | 2. Size of the molecule

Question 45

Drugs with a (high/low) dipole moment have low lipid solubility

Answer 45

High

Question 46

A highly dipolar molecule with a low partition coefficient that does not penetrate into cells

Answer 46

Sulfisoxazole

Question 47

A less dipolar molecule that has a chloroform-water partition coefficient 10 times that of sulfizoxazole and readily penetrates cells

Answer 47

Sulfadiazine

Question 48

Ions of (large/small) diameter penetrate membranes

Answer 48

small diameter

Question 49

T or F: For weak acids and bases, the unionized form, with a favorable partition coefficient, penetrates biological membranes at a much faster rate than the ionized form

Answer 49

True

Question 50

As ionization increases, lipid solubility (increases/decreases) and passage through charged membranes (increases/decreases)

Answer 50

decreases; decreases

Question 51

For all practical purposes, only the (ionized/unionized) form is said to pass through the membrane

Answer 51

Unionized form

Question 52

Which molecules use passive diffusion to move through the membrane?

Answer 52

O2, CO2, fatty acids

Question 53

Which molecule uses facilitated diffusion to pass through the membrane?

Answer 53

Vitamin b12

Question 54

Which molecules use active transport to pass through the membrane?

Answer 54

Sugars, L-amino acids, sodium, potassium, chloride