Question 1

Which of the following best describes the primary strategy eukaryotic cells use to isolate and organize their chemical reactions compared to prokaryotic cells?

Accepted Answer

Eukaryotes use compartmentalization via membrane-enclosed organelles, while prokaryotes rely mainly on spatial separation within the cytoplasm.

Question 2

Which organelles in eukaryotic cells are surrounded by double membranes?

Accepted Answer

Nucleus, mitochondria, and chloroplasts

Question 3

A typical eukaryotic cell has a much larger surface area of endoplasmic reticulum membrane compared to its plasma membrane. If the ER occupies 50% of the total membrane area and the plasma membrane only 2%, what is the ratio of ER to plasma membrane area?

Accepted Answer

$$ \frac{50}{2} = 25 $$

Question 4

Which of the following best describes the relationship between the endoplasmic reticulum (ER) and the nuclear membrane?

Accepted Answer

The ER membrane is continuous with the outer nuclear membrane.

Question 5

Which cell type would you expect to have an abundance of smooth ER, and why?

Accepted Answer

Liver cells, because they are involved in detoxification and lipid metabolism.

Question 6

Which organelles are part of the endomembrane system and communicate with each other via vesicular transport?

Accepted Answer

ER, Golgi apparatus, lysosomes, endosomes, and plasma membrane

Question 7

Which mechanism allows proteins to enter the nucleus, and how does it differ from protein import into mitochondria?

Accepted Answer

Proteins enter the nucleus in their folded conformation via nuclear pores, whereas proteins enter mitochondria unfolded and are translocated across the membrane.

Question 8

If a protein lacks a sorting signal, what is its fate within the cell?

Accepted Answer

It remains in the cytosol.

Question 9

A protein is engineered to have both an ER sorting signal and a nuclear localization signal. Where is it most likely to end up?

Accepted Answer

It will be directed to the ER, as the ER signal sequence is recognized first during translation.

Question 10

Which of the following best describes the function of the signal-recognition particle (SRP) during protein synthesis?

Accepted Answer

SRP binds to the ER signal sequence and pauses translation, then guides the ribosome to the ER membrane.

Question 11

Which of the following is the source of energy for the transport of proteins into the ER?

Accepted Answer

The hydrolysis of GTP and ATP

Question 12

Which pathway describes the directionality and purpose of the endocytic pathway?

Accepted Answer

It moves material from the plasma membrane into the cell, allowing uptake of nutrients and removal of cell surface receptors.

Question 13

Clathrin-coated vesicles select their cargo molecules for transport by:

Accepted Answer

Cargo receptors bind specific molecules, which are then recruited into budding vesicles by adaptor proteins and clathrin.

Question 14

Which covalent modification occurs in the ER and is essential for proper protein folding and stability?

Accepted Answer

N-linked glycosylation

Question 15

What is the fate of misfolded proteins in the ER?

Accepted Answer

They are retained in the ER and eventually targeted for degradation.

Question 16

Which process describes autophagy, and when might a cell use this pathway?

Accepted Answer

Autophagy is the degradation of cellular components in lysosomes, used during starvation or to remove damaged organelles.

Question 17

Which of the following best explains why pinocytosis does not decrease the surface area or volume of a cell?

Accepted Answer

The membrane used to form vesicles during pinocytosis is later returned to the plasma membrane via exocytosis.

Question 18

Cholesterol is transported into the cell cytosol by receptor-mediated endocytosis. Which step is crucial for cholesterol release from its carrier in the endosome?

Accepted Answer

The acidic pH of the endosome causes the LDL receptor to release cholesterol.

Question 19

Which enzyme class is most abundant in lysosomes, and how are these enzymes transported into lysosomes?

Accepted Answer

Hydrolases, transported via mannose-6-phosphate tagging in the Golgi apparatus

Chapter 15: Intracellular Compartments and Protein Sorting: Study Guide for Cell Biology

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