Cell Biology Flashcards
What are the 4 main protein targets for drug action
Ion channels
enzymes
receptors
transporter
2 types of ion channels and how they work
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
Describe the ‘central dogma’
the route from DNA to protein,
DNA is transcribed into mRNA
mRNA is translated into protein
Localisation of common drug targets within the cell
Receptors, Ion channels and transporters are in the membrane
Enzymes are in the cytosol
Describe an off target drug affect
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
what are the components and properties of the cell membrane
properties:
Asymmetrical and dynamic, selectively permeable, structural support, communication
Components: Phospholipids, proteins (ion channels, transporter), other lipids ( cholesterol)
Different ways that molecules travel across the membrane
Passive Diffusion: Ion channels, pores, transporters, across the membrane.
active transport:
use of atp to move against concentration gradient
How does synaptic communication work.
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
What are the 3 types of chemical signalling (communication)
Synaptic, paracrine, endocrine
How does endocrine signalling work
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
How does paracrine signalling work
Most drugs interfere, mimic or modulate communication either between cell or within cells which results in a change in biological outcome
a drug can mimic, modulate or interfere with a receptor on with the chain of intracellular signalling
define intracellular signalling
the mechanism by which the binding of a drug (signal molecule) can cause a change in biological function within a cell
what is are protein kinases
a group of proteins which phosphorylate other proteins
What are the 4 main types of receptors
Nuclear receptors
G protein coupled receptors
ligand gated ion channels
kinase linked receptors
What is the structure of Ligand- gated ion channels, what does the down stream signalling start with and what’s the timescale
Typically 5 subunits in pentameric pore some open the pore and some bind to agonist. downstream signalling starts with ions and timescale is milliseconds
What is the structure of G protein coupled receptors, what does the down stream signalling start with and what’s the timescale
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
What is the structure of kinase linked receptors, what does the down stream signalling start with and what’s the timescale
What is the structure of nuclear receptors, what does the down stream signalling start with and what’s the timescale
Name one signal molecule can bind different receptors have different responses
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
Signal molecules that bind to receptors will be either activators….
modulators or inhibitors
G proteins which bind to the GPCR and their targets
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+)
Describe the cascade which a stimulatory subunits bind to the GCPR
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)
How does Gq(alpha) subunit work
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)
