Pharmacology

Question 1

Define Pharmacology?

Answer 1

The component of medicine that explains the use, mechanisms and effects of drugs

Question 2

Define ‘drug’?

Answer 2

A drug is a chemical substance of know structure (other than a nutrient or dietary factor) which, when administered produces a measurable biological effect

Question 3

What are drugs called that work by blocking a receptor on or within a cell called?

Answer 3

Antagonists

Question 4

What is Pharmodynamics?

Answer 4

This refers to how the drug works and how effective it is on body function

Question 5

What is pharmacokinetics?

Answer 5

This is what the body does to medication and how it does it. It refers to each of the separate components including Absorption, Distribution, Metabolism and Excretion

Question 6

What is meant by bioavailiability?

Answer 6

The percentage of active drug that is administered into a patient that actually makes it into circulation.

Question 7

What are the 2 main ways for excretion of a drug?

Answer 7

Renal excretion- through urine
Hepatobiliary excretion- Lost in faeces

Question 8

What is meant by a single blinded trial?

Answer 8

The volunteers do not know whether they are given the drug or placebo to avoid bias.

Question 9

What is meant by a teratogen?

Answer 9

A substance that can cause abnormalities or birth defects in a developing foetus if the mother takes it.

Question 10

What is an enzyme?

Answer 10

Proteins.
Biocatalysts.
Often modified with lipid, carbohydrates vitamins and metal ions.

Question 11

How do enzymes contribute to metabolism?

Answer 11

Enable control of biochemical reactions.
Enable control of biochemical pathways- One enzyme can act as the rate limiting enzyme which can therefore control the rate of the whole pathway,

Question 12

How do enzymes work?

Answer 12

They lower the activation energy between substrate and product.
Induced fit model. Active site on enzyme changes shape slightly to fit around substrate.

Question 13

How do hydrophobic signalling molecules work?

Answer 13

They repel water so move around the extracellular space bound to a carrier protein. They then get delivered to the target cell where they are then offloaded and can diffuse freely across the cell surface membrane.

Question 14

How do hydrophilic signalling molecules work?

Answer 14

They stay in water but can’t cross the cell membrane so instead bind to transmembrane protein receptors in the cell surface membrane to trigger a response. This is the more common type.

Question 15

What are the 3 stages of cell signalling?

Answer 15

Reception- Receptors bind to ligand
Transduction- Receptor protein changes and activates intracellular molecules (2nd messengers)
Cell Response- The response to the signal.

Question 16

How do G protein coupled receptors work?

Answer 16

They are on the cell surface membrane and cross over the membrane 7 times before ending inside the cell. On this end they are attached to a G protein (made up of 3 subunits- alpha, beta and gamma).
Alpha and gamma subunits are anchored to the cell membrane and keep the G protein right next to the receptor.

Question 17

What do G proteins bind to when they are inactive?

Answer 17

GDP. This is attached to the alpha subunit and cause the 3 subunits to stay together so that the flower is closed.

Question 18

What happens when a ligand binds to a G protein coupled receptor?

Answer 18

This causes a change in shape of the G protein coupled receptor and this allows the G protein to dissociate with GDP and instead bind to GTP which activates the G-protein. This causes the alpha subunit to separate from the others which opens up the G protein so the alpha subunit is free to interact with other molecules.

Question 19

What are the 3 types of G protein? Which ones are stimulatory and which are inhibitory?

Answer 19

Gq- DAG
Gs- adenylate cyclase enzyme- cAMP
Gi- adenylate cyclase (inhibits it- negative feedback on Gs so it inactivates cells)

Gq and Gs are stimulatory and Gi is inhibitory

Question 20

What is an enzyme coupled receptor?

Answer 20

This is where a transmembrane protein has a receptor on the extracellular side and a enzyme on the intracellular side.

Question 21

How do tyrosine kinase receptors work?

Answer 21

Type of enzyme coupled receptor:
2 ligands bind which draws 2 tyrosine chains together forms a dimer.
They then cross phosphorylate each other.
This triggers the signalling pathway.

Question 22

How are tyrosine kinase associated receptors different to tyrosine kinase receptors?

Answer 22

No intrinsic enzyme activity.
Associated with cytoplasmic tyrosine kinase which phosphorylates target proteins to relay signal.

Question 23

How do ion channel receptors work?

Answer 23

They open up once they bind to a specific ligand.
This is how ions such as Na+ and K+ move across the membrane.
A ligand binds to the channel receptor which opens the channel so the ions flow down the concentration gradient.
This results in a shift in electric charge distribution inside the cell causing a cellular response.

Question 24

What is the effect of Km on enzyme affinity?

Answer 24

If Km is high then the enzyme will have lower affinity for its substrate as lots of substrate is required to achieve a fast rate.

If Km is low then the enzyme will have a high affinity.

Question 25

What factors decrease Vmax?

Answer 25

Less expression of genes (so less enzyme formed)
Down regulation of receptors or transporters for an enzyme
Non competitive inhibition of enzymes so substrate can’t bind.

Question 26

What factor increases Km?

Answer 26

Competitive inhibitors- as more enzymes are needed to outcompete the inhibitor which increases Km and therefore a decrease in the affinity of the enzyme.

Question 27

What factors decrease Km?

Answer 27

Enzyme activators which bind to the enzyme and increase the enzyme’s affinity for substrate

Question 28

What is Km?

Answer 28

The affinity of an enzyme for its substrate.

It is determined on a Michaelis Menton graph by half the Vmax and then find the concentration of substrate where v1/2 is.

Question 29

What are the 2 phases of drug metabolism?

Answer 29

Phase 1- Carried out by a class of enzymes where a drug is converted from a non-polar, lipid soluble metabolite to a more polar, water soluble one.

Phase 2- Conjugation reaction- medications are joined with another compound (e.g. methylation). They are highly polar and water soluble so they can’t be absorbed into cells so are eliminated in the urine.

Both phases take place in the liver. Both are affected by Genes, age, liver disease, other medications, foods and supplements

Question 30

What 2 enzymes phosphorylate glucose in humans?

Answer 30

Hexokinase and Glucokinase

Question 31

What is the importance of hexokinase having a lower Km than Glucokinase?

Answer 31

This means that hexokinase can work when blood glucose concentration is lower. However, hexokinase would be fully saturated at lower glucose concentrations so glucokinase is important in order to operate efficiently when blood glucose concentration is higher.

Question 32

What effect does a competitive inhibitor have on Km and Vmax?

Answer 32

No effect on Vmax but Km would increase as more substrate needed to overcome the effect of the inhibitor.

Question 33

What effect does a non-competitive inhibitor have on Vmax and Km?

Answer 33

No effect on Km as inhibitor binds to allosteric site so not outcompeted for active site so the substrate can still bind. However, a successful reaction will not occur so the Vmax will therefore be lower.