Membranes III Flashcards
What is Nexium and what does it do?
1 of biggest selling prescription drugs
- heartburn/stomach ulcers
Inhibits the stomach’s H+/K+ ATPase
What method can be used to measure ion channels?
Patch clamp
Describe patch clamp recording
Small area of membrane hopefully containing channel proteins is removed from a membrane + seals the end of a glass capillary
Current flows when ion channels are open
What are the different types of gating on ion channels?
Voltage gated
Ligand gated
e.g. ACh receptor
Mechanically gated
e.g. in auditory cells
Describe how ion channels are involved in nerve cells
1.Stimulus causes sufficient depolarisation of plasma membrane (exceeds threshold potential) causes voltage-gated Na+ channels to open
- Na+ enters the cell
-> depolarises membrane further
-> causes more Na+ to open
= propagation of action potential - Channels inactivated and then closed (when re-polarised) so membrane isn’t permanently depolarised
Describe the pathway of signals in nerve cells
Neurone receives signal at dendrites
- > Axon conducts signal
- > Terminal branches transmit signal
How does action potential propagate?
Wave of depolarisation
Unidirectional
- away from channels that have been inactivated
What happens at nerve terminals?
Action potential reaches nerve terminals
- > voltage gated Ca2+ channels open
- > Ca2+ enters
- > fusion of vesicles with plasma membrane + release of neurotransmitters
Give an example of a disease caused by defects in ion channels
Cystic fibrosis
- defects in ion channels
-> lung congestion + infections
What are the 3 types of cell surface receptors?
Ion channel linked
G-protein linked
Enzyme linked
Give an example of an enzyme receptor
Insulin receptor
- insulin binds + activates an enzyme (tyrosine kinase)
= phosphorylates proteins
