Question 1

Which of the following best describes the function of the signal recognition particle (SRP) during cotranslational import of proteins into the endoplasmic reticulum (ER)?

Accepted Answer

SRP binds to the ribosome and halts translation, then directs the ribosome-protein complex to the ER membrane by interacting with the SRP receptor.

Question 2

A mutation causes the hydrophobic region of a protein's signal sequence to be shortened. What is the most likely consequence for the protein's localization?

Accepted Answer

The protein will fail to be imported into the ER and remain in the cytosol.

Question 3

Which coat protein is responsible for vesicle formation from the Golgi apparatus destined for the ER, and what is the direction of this transport?

Accepted Answer

COPI; retrograde transport

Question 4

During receptor-mediated endocytosis, which protein is directly responsible for the scission of the vesicle from the plasma membrane?

Accepted Answer

Dynamin

Question 5

Which of the following best explains the mechanism of SNARE-mediated membrane fusion?

Accepted Answer

v-SNAREs on the vesicle and t-SNAREs on the target membrane interact, bringing the membranes close together to facilitate fusion.

Question 6

Which equation best represents the Nernst equation for calculating the equilibrium potential ($$E_{ion}) $$for a given ion across a membrane?

Accepted Answer

$$E_{ion} = \frac{RT}{zF} \ln \left( \frac{[ion]_{out}}{[ion]_{in}} \right)$$

Question 7

Which of the following best describes the role of oligodendrocytes in the nervous system?

Accepted Answer

They myelinate axons in the central nervous system, increasing the speed of electrical signal transmission.

Question 8

A neurotransmitter binds to a GPCR on the postsynaptic membrane. Which of the following is the most immediate effect?

Accepted Answer

Activation of a G protein, which then triggers downstream signaling cascades.

Question 9

In the GPCR pathway, which sequence correctly describes the activation of adenylyl cyclase and its downstream effects?

Accepted Answer

GPCR activation $$\rightarrow Gs$$α activation $$\rightarrow$$ adenylyl cyclase activation $$\rightarrow$$ cAMP production $$\rightarrow$$ PKA activation

Question 10

Which of the following best describes the process of signal amplification in a signaling cascade?

Accepted Answer

A single ligand binding to a receptor can activate multiple downstream molecules, resulting in a large cellular response.

Question 11

Which of the following is a correct sequence of events in the RTK pathway leading to gene expression?

Accepted Answer

Ligand binding $$\rightarrow$$ receptor dimerization $$\rightarrow$$ autophosphorylation $$\rightarrow$$ adaptor protein recruitment $$\rightarrow$$ Ras activation $$\rightarrow$$ MAP kinase cascade $$\rightarrow$$ gene expression

Question 12

Which cytoskeletal element is responsible for the formation of the mitotic spindle during cell division, and what is its subunit?

Accepted Answer

Microtubules; tubulin

Question 13

Dynamic instability of microtubules is characterized by which two processes?

Accepted Answer

Catastrophe and rescue

Question 14

Which protein complex is responsible for promoting branching of actin filaments in lamellipodia?

Accepted Answer

Arp2/3 complex

Question 15

Which motor protein moves toward the plus end of microtubules and is essential for anterograde transport in neurons?

Accepted Answer

Kinesin

Question 16

In muscle contraction, which equation best represents the relationship between force ($$F$$), cross-bridge number ($$n$$), and average force per cross-bridge ($$f$$)?

Accepted Answer

$$F = n 	imes f$$

Question 17

Which cell-cell junction is primarily responsible for preventing paracellular transport and maintaining the polarity of epithelial cells?

Accepted Answer

Tight junctions

Question 18

Which extracellular matrix protein provides tensile strength to tissues and is the most abundant protein in mammals?

Accepted Answer

Collagen

Question 19

A patient has a genetic defect in laminin. Which structure is most likely to be affected?

Accepted Answer

Basal lamina

Cell Biology Study Guide: Endomembrane System, Signaling, Cytoskeleton, Cell Movement, and Cell Interactions

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