GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Action Potentials and Synapses

Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology

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All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

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Example Questions

Example Question #4 : Cellular Processes

Which of the following choices corresponds to what is happening in a cell when an action potential reaches its peak?

Possible Answers:

Voltage-gated sodium channels open

The sodium-potassium pump stops

Sodium channels are inactivated

Potassium channels close

Correct answer:

Sodium channels are inactivated

Explanation:

The peak of an action potential signals the inactivation of sodium channels. This effectively prevents more sodium from entering the cell and halts the depolarization that was previously occurring, resulting in a maximum depolarization value. Potassium channels remain open, and are the cause for the membrane potential to start dropping (positive charge is leaving the cell). The sodium-potassium pump does not stop during this process. In fact, its continued function is essential for eventually restoring the resting membrane potential.

Example Question #11 : Cellular Processes

An action potential occurs in an axon that synapses at a muscle; this specific type of synapse is called a neuromuscular junction. During the action potential, the membrane potential of the axon sharply depolarizes as the signal moves towards the terminal. Upon reaching the synaptic terminal, neurotransmitters are released and interact with receptors on the muscle. Which of the following best summarizes the changes that occur in the post-synaptic muscle after a neurotransmission event?

Possible Answers:

Activation of receptors depletes the muscle of intracellular calcium stores and the muscle depolarizes. 

Activation of receptors opens ion channels, but the membrane potential is unchanged. 

Activation of receptors causes closing of ion channels on the muscle, and the muscle hyperpolarizes. 

Activation of receptors causes opening of ion channels on the muscle, and the muscle depolarizes. 

Activation of receptors causes opening of ion channels on the muscle, and the muscle hyperpolarizes. 

Correct answer:

Activation of receptors causes opening of ion channels on the muscle, and the muscle depolarizes. 

Explanation:

Neurotransmitters will bind their respective receptors on the post-synaptic membrane, which is a muscle in this case. This binding causes changes to other proteins on that membrane, which results in an opening of ion channels. The muscle then depolarizes due to the influx of positively charged ions, and this can be measured as a positive change in the muscle membrane potential. 

Example Question #1 : Help With Action Potentials And Synapses

What protein is responsible for maintaining the resting potential across a neuronal plasma membrane? 

Possible Answers:

Sodium-chlorine pump

Ligand-gated sodium channels

Proton pump

Potassium-ATP transporter

Sodium-potassium pump

Correct answer:

Sodium-potassium pump

Explanation:

The sodium-potassium pump maintains the resting membrane potential by utilizing 1 ATP to transport 2 potassium ions into the cell, and pumping 3 sodium ions out, which makes the inside of the cell negative relative to the outside of the cell. 

Example Question #13 : Cellular Processes

Which phase of the action potential begins when there is a rapid and massive influx of sodium ions into the neuron?

Possible Answers:

Repolarization

Hyperpolarization

Overshoot

Depolarization

Undershoot

Correct answer:

Depolarization

Explanation:

Depolarization, also known as the rising phase, occurs when the membrane potential goes from being negative to positive very quickly. This is instigated by the influx of ions through the open voltage gated channels, and the positive ions make the cell more positive relative to the resting potential.

All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

1 Diagnostic Test 201 Practice Tests Question of the Day Flashcards Learn by Concept
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