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Drug Delivery II > Exam 2 Diffusion > Flashcards

Exam 2 Diffusion Flashcards

1
Q

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

A

Uncombined

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2
Q

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

A

Combined

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3
Q

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

A

True

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4
Q

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

A

Passive diffusion

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5
Q

Fick’s Law equation

A

(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
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6
Q

Permeability constant equation

A

P = D/x, cm/sec

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7
Q

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

A

Patchy

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8
Q

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

A

Mean values

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9
Q

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

A

exponential (first order) mode

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10
Q

When is equilibrium established in the concentration gradient?

A

When c1 = c2

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11
Q

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

A

Blood

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12
Q

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

A

Uncharged

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13
Q

What does Brownian Motion measure?

A

Distance traveled by the molecule

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14
Q

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

A

Spherical particles

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15
Q

What is the radius in angstroms of sucrose?

A

4.4 A

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16
Q

What is the radius in angstroms of albumin?

A

35 A

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17
Q

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

A
  1. Concentration (chemical) gradient

2. Potential difference (electrical gradient) across the membrane

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18
Q

A biological membrane has which charge on the intracellular portion?

A

Negative

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19
Q

A biological membrane has which charge on the outside?

A

Positive

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20
Q

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

A

High kinetic energy

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21
Q

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

A

negative; positive

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22
Q

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

A

concentration difference

“downhill” means moving from higher to lower concentration

23
Q

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

A

with the electrochemical gradient

24
Q

Why might a polyvalent cation never penetrate the membrane?

A

It will be greatly repelled by the outside of the membrane

25
Q

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

A

Facilitated diffusion

26
Q

In facilitated diffusion, particles move (uphill/downhill)

A

Downhill

27
Q

Facilitated diffusion relies on what type of molecule?

A

Carrier molecules

28
Q

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

A

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

29
Q

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

A

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

30
Q

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

A

Active transport

31
Q

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

A

Active transport bitches

32
Q

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

A

phagocytosis; energy dependent; slow; inefficient

33
Q

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

A

Invagination

34
Q

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

A

Adrenal gluccocorticoids

35
Q

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

A

Partitioning

36
Q

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

A

Sol

37
Q

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

A

Diameter

38
Q

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

A

Pores…. rarely pinocytosis

39
Q

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

A

True

40
Q

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

A

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

41
Q

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

A

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

42
Q

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

A

lipid/water partition coefficient

43
Q

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

A

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

44
Q

What two factors determine the partition coefficient of a drug?

A
  1. Polarity

2. Size of the molecule

45
Q

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

A

High

46
Q

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

A

Sulfisoxazole

47
Q

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

A

Sulfadiazine

48
Q

Ions of (large/small) diameter penetrate membranes

A

small diameter

49
Q

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

A

True

50
Q

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

A

decreases; decreases

51
Q

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

A

Unionized form

52
Q

Which molecules use passive diffusion to move through the membrane?

A

O2, CO2, fatty acids

53
Q

Which molecule uses facilitated diffusion to pass through the membrane?

A

Vitamin b12

54
Q

Which molecules use active transport to pass through the membrane?

A

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

Drug Delivery II (10 decks)

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