What is a quantal response? (1)
All or nothing response
What are some factors that affect response? (5)
- Previous Exposure
- Enzyme Activity
- Body Composition
How can Affinity be represented in chemical equation? (2)
Association contant/Dissociation constant
What are the differences between competitive Antagonist and non-competitive Antagonist? (4)
Competitive antagonist - Competes with agonist for same receptor. This slows than effect of agonist but eventually agonist out-competes to produce maximum response.
Non-competitive antagonist - Binds irreversibly with receptor (at active site or different site) so agonist cannot bind. This is allosteric effect to inactivate receptor. Therefore maximum response is NOT obtained.
What is a constitutively-active receptor? What are some examples? (3)
A receptor that produces background activity even without agonist.
The receptor has a slightly more active state than other receptors.
e.g some GABA receptors, histamine receptors.
At what state do agonists have more affinity on receptors? (2)
Agonists have more affinity for receptors when they are in their active state, and less affinity in resting state.
Therefore in active state, the receptor produces increased response.
What is an inverse Agonist? (2)
Opposite effect of agonist, has increased affinity for receptor in resting state, than in active state.
What effect do neutral Antagonists have on receptors? (2)
They have equal affinity for both resting and active states of receptors, hence slow down or stop effect.
Does not have effect on Resting to Active equilibrium.
What does GABA stand for? What does it do?
How does it prevent Action Potential in Brian Cells?
GABA - Gamma aminobutyric acid. It is the predominant inhibitory neurotransmitter in brain.
It binds to GABAa (Ion Channel (Type 1 Recptor)) Receptor in brain and allows Cl- to enter cell to make depolarisation difficult.
This stabilises tissue and produces sedation.
What agonists bind to G-coupled proteins with Beta2 Receptors (Type 2 receptors)?
How does this work and what effect does it produce? (5)
Noradrenaline and Adrenaline.
They bind to Beta 2 receptor, causing activation of G protein.
G Protein activates Adenylyl cyclase.
Adenylyl cyclase activates cAMP (second messenger), which activates Protein Kinase
This leads to Smooth muscle relaxation and Bronchodilation.
How does Asthma lead to Bronchoconstriction?
What drug reverses this? (3)
In Asthma the beta 2 receptor and the intracellular pathway is unresponsive to agonists.
This leads to less smooth muscle relaxation hence bronchoconstriction.
Salbutamol acts as a synthetic agonist to stimulate receptor and leads to Bronchodilation.
What receptors are Type 3 receptors?
How do they work? (3)
When agonist binds to receptor, this triggers a cascade of phosphorylation intracellularly leading to cellular effect.
What receptors are type 4 receptors?
How do they work? (3)
Nuclear (intracellularly) Receptors. Also called Steroid Hormone receptors.
They normally inactive in cytosol but when activated by agonist, they move into nucleus to control gene expression and protein synthesis.
What is the time difference between all the receptor types? (2)
Type 1 receptor (Ion channel linked) acts in milliseconds
Type 2 receptor (G coupled protein) acts in seconds
Type 3 receptor (Enzyme linked) acts in minutes
Type 4 receptors (Nuclear) acts in hours.