Q: Which of the following equations describes the relationship between substrate concentration $$[S]$$ and reaction velocity $$V in $$Michaelis-Menten enzyme kinetics?

$$V = V_{max} \times \frac{[S]}{K_m + [S]}$$

Question 1

Which of the following best describes the role of the myelin sheath in neuronal signal transmission?

Accepted Answer

It decreases the ability of the membrane to retain electrical charge, allowing nerve impulses to spread farther and faster.

Question 2

During an action potential, which sequence of ion movements occurs across the axonal membrane?

Accepted Answer

Inward movement of Na$$^+$$ followed by outward movement of K$$^+$$

Question 3

What is the primary function of voltage-gated sodium channels during the initiation of an action potential?

Accepted Answer

To allow Na$$^+$$ ions to enter the cell, causing depolarization

Question 4

Which of the following statements about channel gating is correct?

Accepted Answer

Channel gating is an all-or-none process; channels are either fully open or fully closed.

Question 5

What is the role of the S4 helix in voltage-gated ion channels?

Accepted Answer

It serves as a voltage sensor, responding to changes in membrane potential.

Question 6

Which process is responsible for the rapid renewal of action potentials along myelinated axons?

Accepted Answer

Saltatory propagation at the nodes of Ranvier

Question 7

A neuron receives an excitatory signal at its dendrites. Where is the action potential most likely to be initiated?

Accepted Answer

At the axon hillock

Question 8

Which of the following best explains the specificity of ion channels for particular ions?

Accepted Answer

The presence of oxygen atoms in amino acids at the center of the channel, forming a selectivity filter

Question 9

What is the effect of acetylcholine binding to its receptor at a neuromuscular junction?

Accepted Answer

It causes depolarization of the postsynaptic cell, leading to muscle contraction.

Question 10

Which of the following equations describes the relationship between substrate concentration $$[S]$$ and reaction velocity $$V in $$Michaelis-Menten enzyme kinetics?

Accepted Answer

$$V = V_{max} 	imes \frac{[S]}{K_m + [S]}$$

Question 11

Which of the following is a direct effect of elevated Ca$$^{2+}$$ concentration in the presynaptic bouton?

Accepted Answer

Mobilization and fusion of neurosecretory vesicles with the plasma membrane

Question 12

Which protein is directly responsible for mediating vesicle docking and fusion during neurotransmitter release?

Accepted Answer

SNARE proteins

Question 13

What is the consequence of cleaving SNARE proteins by botulinum toxin in neurons?

Accepted Answer

Inhibition of vesicle fusion, leading to paralysis

Question 14

Which of the following statements about neurotransmitter receptors is correct?

Accepted Answer

Ionotropic receptors are ligand-gated ion channels that directly mediate ion flow.

Question 15

Which neurotransmitter is most commonly found at vertebrate neuromuscular junctions and is classified as excitatory?

Accepted Answer

Acetylcholine

Question 16

What is the main effect of endocannabinoids in the brain?

Accepted Answer

They inhibit the activity of presynaptic neurons.

Question 17

Which of the following best describes the propagation of an action potential along a myelinated axon?

Accepted Answer

The action potential jumps from one node of Ranvier to the next, a process called saltatory conduction.

Question 18

Which of the following is true regarding the inactivation of voltage-gated ion channels?

Accepted Answer

Inactivation is caused by a particle that inserts into the channel opening, preventing ion flow.

Question 19

Which of the following neurotransmitters is classified as inhibitory and acts at synapses in the central nervous system?

Accepted Answer

GABA ($$\gamma-$$aminobutyric acid)

Cell Biology Study Notes: Membrane Potential, Action Potentials, Synaptic Transmission, and Neurotransmitters

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