VC - Molecular Neuroscience II

Question 1

What is the Kinesin Paradigm transport mechanism?

Answer 1

Kinesin is a motor protein that moves cargo or proteins along microtubules

• Uses ATP
• Facilitates cellular transport
• Acts in giant axons

Question 2

What are the steps involved in Kinesin transport? (5)

Answer 2

1) Kinesin binds to Cargo or protein that needs to be transported

2) Binds to Microtubules.

3) Uses ATP activity.

4) Walk along the microtubule .

5) Move protein to extremities of the processes where the major signalling happens.

Question 3

How are opposite movements in microtubules accomplished?

Answer 3

Dyneins (toward - end)

Kinesins (toward + end)

Question 4

What makes the neuron excitable?

Answer 4

Electrical and Chemical potentials

Question 5

How do neurons communicate?

Answer 5

Neurons use electrical and chemical communication to facilitate intercellular communication

Question 6

What are the key components of sodium channels? (4)

Answer 6

• Made up of one protein sequence that contains 4 domains
• 6 helices are present in each domain
• Each domain has a voltage sensor at the 4th helix (charged amino acid)
• Reentrant loop present between 5 and 6

Question 7

What are the key components of potassium channels? (3)

Answer 7

Potassium Channels are made up of one protein sequence that contains 1 domain

• Each domain has a voltage sensor at the 4th helix
• Come together in a tetramer to make a functional channel

Question 8

What is the threshold for activation and inactivation of Na+ and K+ channels?

Answer 8

Na+

• Threshold for activation about -50 mV
• Threshold for inactivation about 0 mv

K+

• Threshold for activation is about 0 mv
• Threshold for inactivation +50 mV

Question 9

What are the 2 ways to bridge the synaptic gap?

Answer 9

ELECTRICAL SYNAPSE

• Signal passed direct electrical flow between two cells
• Gap junctions and connexins present in the presynaptic membrane

CHEMICAL SYNAPSE

• Electrical signal converted to a chemical signal and then back into an electrical signal
• Involves neurotransmitter release for communication

Question 10

How does neurotransmitter termination occur?

Answer 10

Neurotransmitters diffuse away and are removed by reuptake from the synaptic cleft

Question 11

Processes of a chemical synapse (7)

Answer 11

1. Stimulated neuron opens ion channels including those that allow Ca2+ into nerve terminal.
2. Ca2+ is sensed. Recognized by a protein that binds Ca2+ and changes its conformation (Synaptotagmin)
3. Change in conformation allows proteins SNARE proteins to promote fusion via a vesicle/plasma-membrane protein complex.
4. Vesicle fuses with the plasma membrane, NT released and diffuses into the synaptic cleft.
5. Receptors bind NT and these proteins are ion channels.
6. NT binding opens (or is gates) receptor channel, allows ions to flow and change distribution across membrane.

• Excite by depolarizing the membranes {positive signal}.
• Inhibit by hyperpolarizing the membrane {negative signal}.

7. Chemical signal is terminated by diffusion away or reuptake from the synaptic cleft