Lecture 1 +2 Biological Signal Molecules

Question 1

Define Homeostasis

Answer 1

A system that is same standing,

a dynamic equilibrium maintained at a certain point, by a physiological process, needed to sustain life

Question 2

Define Pharmacodynamics

and Pharmacokinetics

Answer 2

• a drugs action on the body

- the bodys action on a drug

Question 3

Define the Paracrine signalling system

Answer 3

when a signalling molecule is released into the intracelluar space to signal adjacent cells.
molecules are known as local mediators
ie within a tissue

Question 4

Define the Endocrine signalling system

Answer 4

when a signalling molecule enters the blood stream
a hormone
it needs to be soluble hence hydrophillic

Question 5

Define nervous system signalling

Answer 5

neurotransmission - a signalling molecule is released into the a junction between a nerve cell and a nerve/muscle cell.
the molecule is a neurotransmitter

Question 6

How does intracellular signalling work?

Answer 6

a hydrophobic molecule that binds to a carrier protein to be carried through the blood, then once it is released as it is hydrophobic it can cross the cell membrane and bind to a receptor within the cell.
this binding can cause a conformational change within the protein, exposing a DNA binding domain, which can then go on to regulate gene expression

Question 7

Define receptor

Answer 7

a molecule that can recognise a ligand or family of ligands
the binding of a ligand can brings about regulation of a cellular process
when unbound a receptor is silent

Question 8

What is a ligand, what are the types of ligands?

Answer 8

a ligand is any molecule that specifically binds to a receptor site
a ligand activates a change is an agonist
does not activate a change is an antagonist
antagonists directly compete with agonists, by blocking the site, this leads to a reduction in action

Question 9

Name some roles of receptors

Answer 9

cell signalling
neurotransmission
 cellular delivery
cell adhesion
modulate an immune response
control gene expression
sorting of intracellular proteins via organelle membranes 
intracellular siginalling for example to release calcium stores

Question 10

Receptors have a very high binding affinity this means…

Answer 10

they needs a very low concentration of of molecules to bind to the receptor and trigger action

Question 11

Explain how we classify receptors, using acetylcholine as an example

Answer 11

ach is a large family of receptors, we call them ach receptors. They all bind to ach.
we then classify them based on the agonist they have highest affinity for, ie nicotonic receptors for nicotine and muscarinic receptors for muscarine
note that they can bind to either recptor it is just highest affinty
we then subdivide based on the anatagonist which has the highest affinity for that receptor. like M1 M2 M3 for muscarine

Question 12

What is an acceptor?

Answer 12

they will operate in the absence of a ligand

when something joins, it can regulate a proteins activity levels

Question 13

What are the four major classes of receptors?

Answer 13

membrane bound receptors with intergral ion channels
membrane bound receptors with intergral enzyme activity
membrane bound receptors coupled to effectors via transducing proteins
intracellular protiens
this is order of fastest to slowest response

Question 14

give a description of classical ligand gateted ion channels

Are there exceptions?

Answer 14

a gated channel that opens when the singal binds
it has a binding domain then 5 subunits to make the ligand gated pore. this is a classical receptor super family.
there are non classical liganed gated ion channels

Question 15

what is a receptor super family?

Answer 15

a group of receptors that all have a similar strucutre and functional mechanism.

Question 16

why are receptor linked enzymes and ligand gated ion channels less common than other receptors?

Answer 16

they have a higher energetic cost associsated with maintining them.
they need to keep a high affinity receptor and specific enzyme or a specific channel maintianed

Question 17

what is an advantage of tranducing protien receptors?

Answer 17

they provide an intergrated cellular respone
this means one receptor can signal multiple affectors and hence changes within the cell at once
they allow for amplification and cascading within the cell.

Question 18

explain the mechanism for tyrosine kinase (enzyme receptor). an example of this is how insulin works.

Answer 18

the agonist binds to a dimer receptor which causes them to autophosphorylate each other.
this allows the phosphate to activate multiple enzymes within the cell. they themselves can be phosphorylated when activated, activating more enzymes and so on. It can cause a cascade.
alternatively the phospahte can activate a transducer, which may have many different phosphorylation points. This allows for many singalling path ways to be set off within the cell - an integrated response.

Question 19

What is the largest receptor class in the human body?

Answer 19

Receptors linked to transducing protiens (g proteins)

Question 20

What is a Tranducer protien receptor?

give an example

Answer 20

a 7 trans membrane receptor, that is coupled via a g-protien (GTP binding regulatory proteins) to enzymes or channels.
this is how all adrenaline receptors work

Question 21

Explain the mechanism of a transducing protein

Answer 21

a molecule, for example adrenaline will bind to the receptor and activate.
within the cell this will cause gdp to leave the g protien coupling domain, and allow gtp to join, activating the g protien, allowing a sub unit of it to dissociate. This can then go and activate multiple enzymes within the cell.

Question 22

What is an advantage of the g protien system?

Answer 22

it allows for intergration within the cell
cascade responses via amplification
we can have stimulator and inhibitor receptor signals both signal the target enzyme

Question 23

Cellular signalling is useful as it allows for…

Answer 23

Amplification,
one ligand molecule can signal thousands of responses very quickly, through transducer proteins and enzymes
this allows for quick respones

Question 24

what are the molecules that act on glucose levels?

Answer 24

Insulin - Stimulates glycogen synthesis from glucose

glucagon - stimulations glycogen break down into glucose