Cell Biology

Question 1

What are the 4 main protein targets for drug action

Answer 1

Ion channels
enzymes
receptors
transporter

Question 2

2 types of ion channels and how they work

Answer 2

Ligand- gated channels: open only when one or more agonist molecules are bound, and are properly classified as receptors
Voltage gated Channels: gated by changes in the transmembrane potential

Question 3

Describe the ‘central dogma’

Answer 3

the route from DNA to protein,
DNA is transcribed into mRNA
mRNA is translated into protein

Question 4

Localisation of common drug targets within the cell

Answer 4

Receptors, Ion channels and transporters are in the membrane
Enzymes are in the cytosol

Question 5

Describe an off target drug affect

Answer 5

Off-target drug affect is when the drug has an affect an different area of the organism then intended, this can be due to the same target being in use is a different part of the organism with a different function but can still be affected by the drug

Question 6

what are the components and properties of the cell membrane

Answer 6

properties:
Asymmetrical and dynamic, selectively permeable, structural support, communication

Components: Phospholipids, proteins (ion channels, transporter), other lipids ( cholesterol)

Question 7

Different ways that molecules travel across the membrane

Answer 7

Passive Diffusion: Ion channels, pores, transporters, across the membrane.

active transport:
use of atp to move against concentration gradient

Question 8

How does synaptic communication work.

Answer 8

Synaptic - a presynaptic cell releases a neurotransmitter into the synaptic cleft which binds to a receptor on the postsynaptic cell which cause the release of an effector molecule within the post synaptic cell e.g. acetylcholine, serotonin

Close contact, short diffusion distance. quick

Question 9

What are the 3 types of chemical signalling (communication)

Answer 9

Synaptic, paracrine, endocrine

Question 10

How does endocrine signalling work

Answer 10

Normally a hormone is released by a tissue/organ in to the blood stream, reaching everywhere and only having the desired affect is some places.
e.g. testosterone

cells can be very far from each other

Question 11

How does paracrine signalling work

Question 12

Most drugs interfere, mimic or modulate communication either between cell or within cells which results in a change in biological outcome

Answer 12

a drug can mimic, modulate or interfere with a receptor on with the chain of intracellular signalling

Question 13

define intracellular signalling

Answer 13

the mechanism by which the binding of a drug (signal molecule) can cause a change in biological function within a cell

Question 14

what is are protein kinases

Answer 14

a group of proteins which phosphorylate other proteins

Question 15

What are the 4 main types of receptors

Answer 15

Nuclear receptors
G protein coupled receptors
ligand gated ion channels
kinase linked receptors

Question 16

What is the structure of Ligand- gated ion channels, what does the down stream signalling start with and what’s the timescale

Answer 16

Typically 5 subunits in pentameric pore some open the pore and some bind to agonist. downstream signalling starts with ions and timescale is milliseconds

Question 17

What is the structure of G protein coupled receptors, what does the down stream signalling start with and what’s the timescale

Answer 17

7 Transmembrane regions with an N terminus on the outside and a C terminus on the inside.
The ligand binding site is either on the N-terminus or inside the transmembrane structure
the G protein coupling domain is on the inside of the cell

Question 18

What is the structure of kinase linked receptors, what does the down stream signalling start with and what’s the timescale

Question 19

What is the structure of nuclear receptors, what does the down stream signalling start with and what’s the timescale

Question 20

Name one signal molecule can bind different receptors have different responses

Answer 20

Acetylcholine can bind to a cardiac muscle which results in a reduced rate and force of contraction
when it binds to skeletal and smooth muscles causes contraction
in salivary glands in causes secretion

adrenaline stimulates the heart (more blood pumps around the body) and also relaxes the airways

Question 21

Signal molecules that bind to receptors will be either activators….

Answer 21

modulators or inhibitors

Question 22

G proteins which bind to the GPCR and their targets

Answer 22

Gs(alpha): activation of adenylyl cyclase
Gi(alpha): inhibition of adenylyl cyclase
Gq(alpha): activation of phospholipase C
Gi(beta/gamma): opening ion channels(k+)

Question 23

Describe the cascade which a stimulatory subunits bind to the GCPR

Answer 23

the subunit binds to the GCPR then Gs(alpha) binds to the C terminus, this activates the first effector, adenylyl cyclase (AC) which turn ATP into cAMP(2nd messenger). cAMP will activate the second effector called protein kinase A(PKA)

Question 24

How does Gq(alpha) subunit work

Answer 24

it activates a phospholipase C protein, this takes lipid component of the membrane called PIP2 and turns it into 2 secondary messengers DAG and IP3. this increases the concentration of Ca2+ in the cell which activates protein kinase C (PKC)