Cell Biology and Drug Targets

Question 1

Which type of transcription factors are involved in cell differentiation?

Answer 1

Yamanaka factors

Question 2

Give 4 examples of post-translational modification of proteins

Answer 2

• Glycosylation
• Phosphorylation
• Lipidation
• Acetylation

Question 3

Which organelle generates new ribsomes?

Answer 3

Nucleolus

Question 4

What are the 4 major drug targets?

Answer 4

• Receptors
• Enzymes
• Transporters
• Ion Channels

Question 5

Give 4 effects of phosphorylation on proteins

Answer 5

• in enzymes generate binding sites
• increase/decrease acitivity
• mark proteins out for degradation
• binding of proteins together

Question 6

Give an example of an intracellular receptor

Answer 6

Steroid receptors in cytoplasm

Question 7

What are the 4 types of signalling?

Answer 7

• Intercellular signalling
• Paracrine signalling
• Endocrine signalling
• Synaptic signalling

Question 8

How many transmembrane domains do GPCR contain?

Answer 8

7

Question 9

Give 3 examples of drugs which act on GPCRs

Answer 9

• Propanolol
• Salbutamol
• Atropine

Question 10

Give an example of an enzyme coupled receptor

Answer 10

Receptor tyrosine kinase

Question 11

How is an enzyme coupled receptor activated when something binds?

Answer 11

Binding causes cross-linking (which activates the enzyme)

Question 12

What do nuclear receptors generally regulate?

Answer 12

Gene transcription

Question 13

How do steroid hormones cause a change in protein synthesis?

Answer 13

• Hormones bind and cause hydrophobic molecules to diffuse into the cytosol
• These molecules bind to cytoplasmic binding protein which allows the molecule to enter the nucleus
• This alters gene expression
• Which alters protein synthesis

Question 14

What is a full agonist?

Answer 14

A drug which induces a maximum tissure response

Question 15

How are enzyme coupled receptors acitvated?

Answer 15

The binding of a ligand causes cross linking

Question 16

What are receptor tyrosine kinases often receptors for?

Answer 16

Growth factors

Question 17

What is the link between receptor tyrosine kinases and cancer?

Answer 17

RTK pathways are often mutated in cancer cells. Because RTKs are involved in gene regulation and cell growth

Question 18

Why are enzymes important drug targets?

Answer 18

• They are an important part of signalling cascades
• Some drugs are not active so require an enzyme to convert the drug into an active form

Question 19

Give an example of a drug which acts on an enzyme

Answer 19

Aspirin acts on COX -1 and COX-2 enzymes

Question 20

What is the structure of a channel mediated transporter?

Answer 20

A protein with a pore down the centre

Question 21

What is the structure of a transporter-mediated protein?

Answer 21

Contain abinding pocket for a molecule, once bound the transporter can flip 180º to allow the molecule through the membrane

Question 22

Are transporter-mediated proteins faster or slower than pore/channel proteins?

Answer 22

Slower

Question 23

What are the 3 types of transporters?

Answer 23

• Uniport
• Symport
• Antiport

Question 24

What is a uniport transporter?

Answer 24

A transporter which only transports one product in one direction

Question 25

What is a symport transporter?

Answer 25

A transporter which transports two things in the same direction at the same time

Question 26

What is an antiport transporter?

Answer 26

A transporter which transports two substances in opposite directions at the same time

Question 27

Give an example of a passive transporter

Answer 27

The glucose transporter

Question 28

Give an example of an active transporter

Answer 28

Na+/K+ ATPase

Question 29

What class of enzyme do active transporters require?

Answer 29

ATPase

Question 30

Give a mechanism for how some transporters work

Answer 30

* Transporter has a binding site on one side * binding of a ligand causes conformational shape change * this causes the transporter to close on one side and open on the other side

Question 31

What is the ratio of transport for Na+/K+ ATPase?

Answer 31

3 Na+ in for every 2K+ out

Question 32

Give an example of a drug which acts on the Na+/K+ ATPase

Answer 32

Digoxin

Question 33

What effect does digoxin have on: a) Na+/K+ APTase b) Heart rate?

Answer 33

a) Blocks it b) Increases strength of contraction and increases heart rate due to greater depolarisation in muscle cells

Question 34

Are all ion channels passive?

Answer 34

yes

Question 35

What is the specificity of an ion channel determined by?

Answer 35

Size and charge of the molecule

Question 36

In which direction does movement of ions through an ion channel occur?

Answer 36

Down a concentration gradient

Question 37

What is the function of Gs (α) subunit?

Answer 37

Activates adenylyl cyclase

Question 38

What is the function of Gi (α) subunit?

Answer 38

Inhibition of adenylyl cyclase

Question 39

What is the function of Gq(α)?

Answer 39

Activation of phospholipase c

Question 40

What is the function of Gi (βγ)?

Answer 40

Opening K⁺ ion channels

Question 41

Which ligand-gated ion channel is involved in insulin secretion from β-cells?

Answer 41

ATP sensitive K+ channels

Question 42

Outline how glucose stimulates insulin secretion from β cells in the pancreas

Answer 42

* Intracellular glucose levels rise and cause a rise in [ATP] as respiration rate increases * ATP binds to K⁺ channel and prevents movement of K⁺, causing depolarisation * This causes the opening of voltage gated Ca²⁺ channels and increased [Ca²⁺] causes storage granules to release insulin