Question 1

Late endosomes are also referred to as _______.

Accepted Answer

Late endosomes are commonly referred to as multivesicular bodies (MVBs). Therefore, both the choices "multivesicular bodies" and "MVBs" are correct. "Lateosomes" is not a commonly used term for late endosomes. "Multivertiginous bodies" is a wrong term and is not used to describe late endosomes.

Question 2

Drugs that lower blood LDL levels are referred to as _______.

Accepted Answer

The drugs that lower blood LDL levels are referred to as statins. The other options do not relate to this particular concept.

Question 3

The targeting sequence of mitochondrial-matrix proteins is found at the molecule's N-terminus and includes a number of positively charged residues.What is this targeting sequence called?

Accepted Answer

The targeting sequence found at the N-terminus of mitochondrial-matrix proteins is called the presequence. This presequence typically contains a number of positively charged residues that facilitate the protein's import into the mitochondrial matrix.

Question 4

What leads to the degradation of the contents of late endosomes by lysosomal enzymes?

Accepted Answer

Late endosomes containing intralumenal vesicles can fuse with lysosomes, allowing for the degradation of the contents by lysosomal enzymes. This is the primary way that late endosomes are degraded.

Question 5

How many subcompartments do peroxisomes have into which an imported protein can be placed?

Accepted Answer

Peroxisomes have two subcompartments, the matrix and the peroxisomal membrane, into which an imported protein can be placed.

Question 6

Which phosphoinositide is localized at the late endosome boundary membrane?

Accepted Answer

PI(3,5)P is the phosphoinositide localized at the late endosome boundary membrane. PI(3,5)P is involved in regulating membrane trafficking and endocytic pathways.

Question 7

Typically,receptors for hormones or growth factors are destroyed during endocytosis,leading to a reduction in the cell's sensitivity to further stimulation by that particular hormone or growth factor.This is a mechanism by which cells regulate their ability to respond to extracellular messengers.What is it called?

Accepted Answer

The process described in the question is known as receptor down-regulation.

Question 8

Which of the following is a mitochondrial subcompartment into which proteins can be delivered?

Accepted Answer

Proteins can be delivered to all the mentioned mitochondrial subcompartments: the outer mitochondrial membrane, inner mitochondrial membrane, intermembrane space, and matrix.

Question 9

Which endosomes are typically located in the more interior part of the cell,near the nucleus?

Accepted Answer

Late endosomes are typically located in the more interior part of the cell, near the nucleus, where they play a role in sorting and delivering cargo to lysosomes for degradation.

Question 10

The drugs that lower LDL concentration in the blood function by ________.

Accepted Answer

Drugs that lower LDL concentration in the blood function by blocking a key cholesterol synthesis enzyme, HMG CoA reductase. This class of drugs is commonly known as statins. By inhibiting this enzyme, the liver cells produce less cholesterol, resulting in lower levels of LDL in the bloodstream.

Question 11

Which of the following organelles imports proteins in their native,folded conformation?

Accepted Answer

Peroxisomes are unique among organelles in their ability to import proteins that are already folded in their native conformation. Other organelles typically import proteins in an unfolded state.

Question 12

Which endosomes are typically located near the peripheral region of the cell?

Accepted Answer

Early endosomes are typically found in the periphery of the cell, as they are involved in sorting and recycling of material entering the cell via endocytosis. Late endosomes, in contrast, are located closer to the nucleus and are involved in degradation of material. Medial lysosomes and medial endosomes are not commonly used terms in cell biology, and intellosomes are not a known organelle.

Question 13

What are the differences between early and late endosomes?

Accepted Answer

Early endosomes mature into late endosomes by exchanging Rab5 for Rab7, have a lower pH, and develop internal vesicles.

Question 14

What recognizes ubiquitinated signaling receptors and sorts them into the membranes that give rise to the internal vesicles of the late endosomes?

Accepted Answer

ESCRT complexes recognize and sort ubiquitinated signaling receptors into the membranes that give rise to the internal vesicles of the late endosomes.

Question 15

People with Niemann-Pick type C disease suffer from what defect?

Accepted Answer

Niemann-Pick type C disease is caused by a defect in the proteins needed to transport cholesterol out of lysosomes, leading to an accumulation of cholesterol in various tissues. It is an autosomal recessive disorder, and symptoms may include progressive neurological deterioration, hepatosplenomegaly, and pulmonary involvement. A and B are incorrect because they do not relate to the specific defect seen in Niemann-Pick type C disease. C and E are incorrect because they describe defects in the receptors or enzymes involved in cholesterol metabolism, which are not directly related to lysosomal transport.

Question 16

How many mitochondrial subcompartments exist into which proteins can be delivered?

Accepted Answer

Mitochondria have four main subcompartments: the outer membrane, the intermembrane space, the inner membrane, and the matrix. Proteins can be delivered to any of these subcompartments depending on their function and targeting signals.

Question 17

Where does the PTS receptor bind to peroxisome-destined proteins?

Accepted Answer

The PTS receptor (peroxisome targeting signal receptor) binds to peroxisome-destined proteins in the cytoplasm (cytosol), before they are translocated to the peroxisome membrane.

Question 18

Signaling receptors are usually marked for endocytosis and subsequent destruction by the covalent attachment of a "tag" to the cytoplasmic tail of the receptor while it resides at the cell surface.What is the name of the "tag"?

Accepted Answer

The "tag" that is covalently attached to the cytoplasmic tail of signaling receptors to mark them for endocytosis and subsequent destruction is called ubiquitin.

Question 19

What protein is associated with HDL particles?

Accepted Answer

Apolipoprotein A-1 is the protein most commonly associated with HDL particles.

Question 20

Which of the following organelles imports proteins through one or more outer boundary membranes?

Accepted Answer

All of these organelles import proteins through their outer boundary membranes. The nucleus, mitochondria, chloroplasts, and peroxisomes all have mechanisms to import proteins necessary for their functions.

Quiz 8: Cytoplasmic Membrane Systems: Structure, function, and Membrane Trafficking