01 | Introduction Flashcards
What can be used as a measure of neuron activity?
Rate of ATP synthesis by mitochondria in neuron
What are STORAGE GRANULES?
Holds vesicles at the presynaptic membrane
RMP for normal human neurons is around…(value)
-70 mV
How thick is the cell membrane? (value)
6 nm
When ions pass through passively, they use __. When actively, they use __.
- Ion channels
2. Transport molecules (pumps, transporters)
3 components of an ion channel
- Pore
- Selectivity filter
- Channel gate
__ channel has increased probability of being open. ___ channel has decreased probability of being open.
- Activated
2. Deactivated
Define: inactivation
(@ electrical synapses) conformational change prevents channel from opening, even if there is a stimulus
Define: desensitization
(@ chemical synapses) conformational change prevents channel from opening, even if there is a stimulus
Define: open channel block
something is physically occluding the pore
Explain voltage clamp
The voltage clamp is an experimental method to measure the ion currents while holding the membrane voltage at a set level.
Whole cell patch clamp
- Mimic real cell
- Change intracellular concentrations
Outside out patch clamp
- isolate channels
- change extracellular conc.
Inside-out patch clamp
- Isolate channels
- Change intracellular concentrations
- Example receptors activated by intracellular ligands
How many subunits does nAChR have? List them. What are the requirements?
5 subunits (α, β, γ, δ) that come together – any combination, but has to have at least 2 α (this becomes the ligand binding site)
How many times does each subunit in nAChR cross the membrane? Which segment forms the pore?
4 times (M1-4) M2 forms pore
How does pore open on nAChR?
M helices rotate toward channel wall
What are the 3 voltage-gated channels with similar morphologies? What is that morphology?
- Na, Ca, K
- 4 α subunits with 5 TM regions in each subunit (S1-6)
- 3rd residue of S4 is positive
What does the positive residue in voltage-gated channels do?
- Voltage sensor
- Couples voltage changes in the membrane to channel opening mechanisms
What are the additional subunits on Na channels? What are they used for?
2 TM β
- Activation and gating
Subunits of v-gated Ca channel
4 α1 subunits
What are the additional subunits on v-gated Ca channels? What are they used for?
Intracellular β, TM δ, extracellular α2
- Activation and gating
How does the AA sequence of v-gated K channels compare to other v-gated ion channels?
v-gated K channels have shorter AA sequence
What are the additional subunits on v-gated K channels? What are they used for?
Intracellular β + first few residues from N-terminal form the ball-and-chain inactivation gate
Which TM segments on v-gated K channels form the pore (P-loop)?
S5-6
