Question 1

Which type of cell signaling involves the release of hormones into the bloodstream to reach distant target cells?

Accepted Answer

Endocrine signaling

Question 2

A neuron releases a neurotransmitter that crosses a synapse to stimulate a target cell. Which signaling mechanism is this an example of?

Accepted Answer

Synaptic signaling

Question 3

Which of the following molecules would most easily diffuse across a synthetic lipid bilayer?

Accepted Answer

CO$$_2$$

Question 4

A cell receives multiple signals: one for survival, one for division, and one for differentiation. If the cell only receives the survival signal, what is the most likely outcome?

Accepted Answer

The cell will survive but not divide or differentiate.

Question 5

Which of the following best describes the function of a GEF (guanine nucleotide exchange factor) in the regulation of monomeric GTPases?

Accepted Answer

It promotes the exchange of GDP for GTP, activating the GTPase.

Question 6

Which of the following is true regarding the speed of cellular responses to extracellular signals?

Accepted Answer

Responses that alter protein function are generally faster than those that alter gene expression.

Question 7

A cell's response to a signaling molecule follows a sigmoidal curve. What does this indicate about the response?

Accepted Answer

The response is cooperative, with a threshold before a rapid increase.

Question 8

Which of the following statements about GPCR (G-protein coupled receptor) activation is correct?

Accepted Answer

The activated receptor promotes exchange of GDP for GTP on the G-protein.

Question 9

Which type of membrane transport protein can move solutes against their concentration gradient using energy from ATP hydrolysis?

Accepted Answer

Transporter protein (active transport)

Question 10

Which of the following best explains why ions such as Na$$^{+}$$ and K$$^{+}$$ have low permeability across a synthetic lipid bilayer?

Accepted Answer

They are charged and interact unfavorably with the hydrophobic core.

Question 11

A transporter protein moves glucose into a cell along with Na$$^{+}$$ ions, both in the same direction. What type of transport is this?

Accepted Answer

Symport

Question 12

Which of the following is a key difference between channel proteins and transporter proteins?

Accepted Answer

Channel proteins allow rapid movement of specific ions or water, while transporters bind and move solutes more slowly.

Question 13

The rate of transporter-mediated diffusion reaches a maximum (V$$_{max}) at $$high substrate concentrations. What is the main reason for this?

Accepted Answer

The transporter becomes saturated with substrate.

Question 14

Which of the following best describes the function of the Na$$^{+}/K$^{+}$$ pump in animal cells?

Accepted Answer

It uses ATP to move Na$$^{+}$$ out and K$$^{+} in$$, maintaining ion gradients.

Question 15

A cell is placed in a solution with a high concentration of K$$^{+}$$ outside and low K$$^{+}$$ inside. If K$$^{+}$$ channels open, what will happen to the membrane potential?

Accepted Answer

The membrane potential will become more positive inside.

Question 16

Which of the following is an example of active transport?

Accepted Answer

Na$$^{+}/K$^{+}$$ ATPase pump

Question 17

Which of the following best describes the role of ABC transporters?

Accepted Answer

They use ATP to transport a variety of small molecules across membranes.

Question 18

A patient is given a drug that inhibits GAP (GTPase-activating protein) activity. What is the most likely effect on monomeric GTPase signaling?

Accepted Answer

GTPase will be constitutively active in the GTP-bound state.

Question 19

Which of the following best explains why steroid hormones can cross the plasma membrane while ions cannot?

Accepted Answer

Steroid hormones are small and hydrophobic, allowing them to dissolve in the lipid bilayer.

Cell Signaling and Membrane Transport: Biochemistry Study Guide

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