Module 4c: Membrane Transport

Question 1

Must be high enough to produce desired effect, but not too high to cause negative effects.

Answer 1

Drug concentration

Question 2

The concentration of a drug at its site of action is called ____.

Answer 2

drug efficacy

Must get the drug to the receptor it will work on.

Question 3

What does ADME stand for?

Answer 3

A. Absorption (enters into blood stream)
D. Distribution (contact with receptor)
M. Metabolism (leave receptor and journey to metab site)
E. Excretion (removal)

Question 4

What are biological membranes made up of?

Answer 4

Phospholipids! :)

Question 5

The head of the phospholipid is ____?

Answer 5

Polar and hydrophilic.

*makes up the extracellular & intracellular walls

Question 6

The tails of the phospholipids are ____?

Answer 6

Non-polar & Hydrophobic

*makes up the inner layer of the PLB

Question 7

How do we get drugs into the cell?

Answer 7

Via transporters, passive diffusion, channels

Question 8

Are transporter’s proteins?

Answer 8

YES!

*so are channels

Question 9

What are the types of transport?

Answer 9

Passive & Active

Question 10

This transport type requires no energy and follows its [ ] gradient.

Answer 10

Passive transport

*LMW drugs have an easier time crossing

Question 11

This type of transport requires ATP and involves influx & efflux.

Answer 11

Active transport

*requires transport proteins

Question 12

What does it mean when you have hit a transport plateau?

Answer 12

At higher drug concentrations that require Active transport, you have a limited number of transporters that can deliver the drug across the membrane.

This can lead to competition with structurally similiar compounds.

*Methotrexate (similiar to folic acid); they may compete :O

Question 13

What two things (about the drug) affect transport & distribution?

Answer 13

1. Drug Size
2. Drug Charge

Question 14

Is <50 Da considered small for drug size?

Answer 14

YES!
* Can be referred to as “Bulk Flow” (passive diffusion)
* Easy to move across
* works in ionized or unionized

4 carbons = 48 Da

Question 15

What is the main way drugs move across membranes?

Answer 15

Passive diffusion

Question 16

What is a Da (Dalton)?

Answer 16

1 gram/mol

*used for proteins (very large molecules)

Question 17

If a drug is ionized, will it be easy to move across the membrane?

Answer 17

No. It will be harder.

*It is also dependent on the pH and pKa.

Question 18

Lipophilic drugs (>50Da) use passive transport but what is also special about these drugs in order for them to move throughout the body?

Answer 18

Need to be balanced lipophilic and hydrophilic.

Question 19

If a drug is unionized, will it be easier for it to cross the membrane?

Answer 19

Yes. This means it is uncharged.