Question 1

Which membrane proteins use the electrochemical gradient to move ions across the membrane? Choose all that apply.
A) Symporters
B) Pumps
C) Antiporters
D) Ion channels

Accepted Answer

AND D.
 All these types of transport use electrochemical gradients to move ions across the membrane. For symporters the electrochemical gradient of one ion is used to drive another ion in the same direction, up its electrochemical gradient. For antiporters, the electrochemical gradient of one ion is used to drive another ion in the opposite direction, up its electrochemical gradient.

Question 2

In transportation within neurons, which direction is retrograde? Which direction is anterograde?

Accepted Answer

Retrograde refers to movement toward the cell body. Anterograde refers to movement down an axon, away from the cell body.

Question 3

List in order of size: neurofilaments, microtubules, microfilaments.

Accepted Answer

Microfilaments < neurofilaments < microtubules

Question 4

Changes in ion conductance or ion concentration can alter the resting membrane potential of a cell. For each of the following, write in the letter indicating whether each condition would cause hyperpolarization (H), depolarization (D), or very little change (LC) in the resting membrane potential, and the reason for this change. $\begin{array}{lll}
\text { Condition } & \begin{array}{l}
\text { Membrane } \
\text { potential } \
\text { change }
\end{array} & \text { Reason } \
\text { ncrease in }\left[\mathrm{K}^{+}\right]_{0} &\text{ ----------- }  &\text{ ----------- } \
\text { increase in }\left[\mathrm{Na}^{+}\right]_{0} & \text{ ----------- }& \text{ ----------- }\
\text { increase in } \mathrm{K}^{+} \text {permeability } & \text{ ----------- } & \text{ ----------- }\
\text { increase in } \mathrm{Na}^{+} \text {permeability } & \text{ ----------- } & \text{ ----------- }\
\end{array}$

Accepted Answer

The answer of Changes in ion conductance or ion concentration...

Question 5

What is the function of exocytosis? Choose all that are correct.
A) To take proteins to the plasma membrane
B) To take proteins away from the plasma membrane
C) Potential degradation of proteins
D) To secrete proteins from the cell

Accepted Answer

Exocytosis does not take proteins to the plasma membrane, as that is a form of transportation.

Question 6

Proteins that are destined for export from the cell or that are inserted into the lipid bilayer are synthesized in/on which organelle?
A) Free ribosomes
B) Endoplasmic reticulum
C) Golgi apparatus
D) Nucleus

Accepted Answer

Proteins that are destined for export from the cell or that are inserted into the lipid bilayer are synthesized on the endoplasmic reticulum, which is responsible for protein synthesis and modification before export or insertion into the membrane. Free ribosomes synthesize proteins that will remain inside the cytoplasm of the cell. The Golgi apparatus is responsible for further modification and sorting of proteins before they are shipped out of the cell. The nucleus is responsible for DNA replication and transcription.

Question 7

The brains of patients with Alzheimer's disease show degradation of microtubule function, in part from over-phosphorylation of the microtubule-associated protein, tau. What might happen to neurons when microtubule function is disrupted?

Accepted Answer

The answer of The brains of patients with Alzheimer's disease...

Question 8

Which membrane proteins require ATP to move ions across the membrane? Choose all that apply.
A) Symporters
B) Pumps
C) Antiporters
D) Ion channels

Accepted Answer

Pumps require ATP. The other choices use electrochemical gradients as the energy to move ions across the membrane.

Question 9

What is the transcription unit?
A) The part of the gene that serves as a template for RNA synthesis
B) The part of RNA that serves as a template for protein synthesis
C) The part of the gene that serves as a template for protein synthesis
D) The unit of RNA that is made from a particular gene

Accepted Answer

The transcription unit is the part of the gene that serves as a template for RNA synthesis. It includes the DNA sequence that is transcribed by RNA polymerase, the promoter region that signals the start of transcription, and any regulatory elements that control gene expression.

Question 10

What helps maintain the ion concentration across the membrane of neurons? A) The driving force for any ion B) Na⁺/K⁺ ATPase C) Leak K⁺ channels D) Leak Na⁺ channels

Accepted Answer

Na+ and K+ leak into and out of the cell down their concentration gradient. This slow leak is countered, in part, by the Na+/K+ ATPase that uses ATP to move K+ into the cell and Na+ out of the cell, against their concentration gradient. Answer (a) is incorrect as the driving force is simply the difference in concentration gradient and equilibrium potential.

Question 11

According to the Goldman-Hodgkin-Katz equation, if the membrane were more permeable to Na⁺ at rest, instead of K⁺, what would the approximate resting membrane potential be? A) -70 mV B) +50mV C) -79 mV D) +100mV

Accepted Answer

If we assume that the permeabilities to Na⁺ and K⁺ were reversed then the voltage across the membrane would be close to E_Na (which is about +50 to +55mV). In the Goldman-Hodgkin-Katz equation, the contributions of K⁺ and Cl^- (and other ions) would be relatively small and there would be a large contribution from Na⁺, so the voltage across the membrane would be close to E_Na.

Question 12

Label depolarization, repolarization, and hyperpolarization in Figure Q2-14.  Figure Q2-14

Accepted Answer

The answer of Label depolarization, repolarization, and hyperpolarization in Figure...

Question 13

What kinds of organelles have been localized to dendrites?
A) Polyribosomes
B) ER
C) Golgi
D) All of the above
E) None of these are located in dendrites.

Accepted Answer

All of the listed organelles have been localized to dendrites through various experimental methods such as live-cell imaging and electron microscopy. Polyribosomes are important for protein synthesis, the ER is important for protein folding and lipid synthesis, and the Golgi is important for protein modification and sorting.

Question 14

What is the function of endocytosis? Choose all that are correct.
A) To take proteins to the plasma membrane
B) To take proteins away from the plasma membrane
C) Potential degradation of proteins
D) To secrete proteins from the cell

Accepted Answer

Endocytosis takes proteins from the extracellular space and the membrane into the cell.

Question 15

Figure Q2-10 shows an interpretive drawing of a microtubule moving rightward on a glass slide to which a substance purified from squid axoplasm had been immobilized, in the presence of ATP.  Figure Q2-10
A. What is the substance that was purified that allows movement of the microtubule?
B. What would happen if a non-hydrolyzable form of ATP was added to the solution?

Accepted Answer

The answer of Figure Q2-10 shows an interpretive drawing of...

Question 16

Which equation is used to determine the equilibrium potential of any ion?
A) Ohm's law
B) The driving force
C) The Nernst potential
D) The Goldman-Hodgkin-Katz equation

Accepted Answer

The answer of Which equation is used to determine the...

Question 17

The equilibrium potential for any ion is the point at which two forces/gradients balance each other. What are the two forces/gradients?

Accepted Answer

The answer of The equilibrium potential for any ion is...

Question 18

What does 'local protein translation' mean in neurons?
A) Proteins are synthesized only in the nucleus.
B) Proteins are synthesized only in the cell body.
C) Proteins can be synthesized in dendrites.
D) Proteins can be synthesized by a neighboring neuron.

Accepted Answer

In neurons proteins can be synthesized in dendrites because the molecular machinery to make proteins is located there.

Question 19

Proteins that function in the cytoplasm and nucleus are synthesized in/on which organelle?
A) Free ribosomes
B) Endoplasmic reticulum
C) Golgi apparatus
D) Nucleus

Accepted Answer

Proteins that function in the cytoplasm and nucleus are synthesized on free ribosomes located in the cytoplasm.

Question 20

In the cochlea of the ear sounds waves are turned into electrical signals through special cells called hair cells. When a wave travels through the cochlea it moves the 'hairs' and opens ion channels that are permeable to K⁺ and Ca²⁺. These 'hairs' are in a fluid that has a very high K⁺ concentration compared to the inside of the cell. A. When the ion channels open, in what direction do K⁺ ions flow and why? B. Based on this relative concentration difference of K⁺, what do you predict the equilibrium potential for K⁺ will be: positive, negative or zero?

Accepted Answer

The answer of In the cochlea of the ear sounds...

Quiz 2: Signaling Within Neurons

Which membrane proteins use the electrochemical gradient to move ions across the membrane? Choose all that apply.

In transportation within neurons, which direction is retrograde? Which direction is anterograde?

List in order of size: neurofilaments, microtubules, microfilaments.

What is the function of exocytosis? Choose all that are correct.

Proteins that are destined for export from the cell or that are inserted into the lipid bilayer are synthesized in/on which organelle?

The brains of patients with Alzheimer's disease show degradation of microtubule function, in part from over-phosphorylation of the microtubule-associated protein, tau. What might happen to neurons when microtubule function is disrupted?

Which membrane proteins require ATP to move ions across the membrane? Choose all that apply.

What is the transcription unit?

What helps maintain the ion concentration across the membrane of neurons?

According to the Goldman-Hodgkin-Katz equation, if the membrane were more permeable to Na+ at rest, instead of K+, what would the approximate resting membrane potential be?

Label depolarization, repolarization, and hyperpolarization in Figure Q2-14. Figure Q2-14

What kinds of organelles have been localized to dendrites?

What is the function of endocytosis? Choose all that are correct.

Which equation is used to determine the equilibrium potential of any ion?

The equilibrium potential for any ion is the point at which two forces/gradients balance each other. What are the two forces/gradients?

What does 'local protein translation' mean in neurons?

Proteins that function in the cytoplasm and nucleus are synthesized in/on which organelle?

According to the Goldman-Hodgkin-Katz equation, if the membrane were more permeable to Na⁺ at rest, instead of K⁺, what would the approximate resting membrane potential be?