Question 1

The inner leaflet of the plasma membrane contains elevated levels of _____, which plays an important role in the recruitment of proteins involved in clathrin-mediated endocytosis, like dynamin and AP2. A)PI(4,5)P₂ B)PI(4)P C)PI(3,5)P₂ D)PI(3,4)P₂ E)PI(5)P

Accepted Answer

PI(4,5)P2 (Phosphatidylinositol 4,5-bisphosphate) is known for its role in clathrin-mediated endocytosis, where it recruits proteins such as dynamin and AP2 to the plasma membrane.

Question 2

What leads to the degradation of the contents of late endosomes by lysosomal enzymes?
A)secretion of lysosomal enzymes into late endosomes
B)transport of lysosomal enzymes into late endosomes through specialized pore complexes
C)fusion of late endosomes containing intralumenal vesicles with a lysosome
D)fusion of early endosomes with lysosomes; late endosomes lowering their internal pH activating the enzymes
E)late endosomes synthesizing lysosomal enzymes that then degrade the contents

Accepted Answer

The degradation of the contents of late endosomes is achieved by the fusion of late endosomes with lysosomes. This leads to the formation of an intermediate organelle known as the endolysosome, where the luminal contents of the late endosome are degraded by lysosomal enzymes. The degradation is made possible by the transport of lysosomal enzymes into the endolysosome through specialized pore complexes. This process is facilitated by the presence of intralumenal vesicles within the late endosome, which increase the surface area available for the fusion with lysosomes.

Question 3

How many mitochondrial subcompartments exist into which proteins can be delivered?
A)1
B)2
C)3
D)4
E)5

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 4

Which of the differences between early and late endosomes outlined below is NOT correct?
A)Early endosomes exchange their Rab5 proteins for Rab7 proteins as they transform into late endosomes.
B)Late endosomes have a population of vesicles crowding their interior; early endosomes do not.
C)Late endosomes exhibit a higher pH than early endosomes.
D)In late endosomes, the outer boundary membrane has budded inward on its lumenal surface creating a group of vesicles.
E)All of these are correct.

Accepted Answer

Late endosomes actually exhibit a lower pH than early endosomes, not higher. This acidic environment is crucial for the sorting and processing of cargo.

Question 5

What protein is associated with HDL particles?
A)Large LDL particle B-100
B)LDLenin
C)apolipoprotein B-100
D)statin
E)apolipoprotein A-1

Accepted Answer

Apolipoprotein A-1 is the protein that is specifically associated with HDL particles.

Question 6

People with Niemann-Pick type C disease suffer from what defect?
A)They lack one of two lysosomal enzymes.
B)They cannot degrade HDL particles.
C)They cannot degrade LDL particles.
D)They lack one of the proteins needed to transport cholesterol out of lysosomes.
E)Their LDL receptors are nonfunctional.

Accepted Answer

Niemann-Pick type C disease is a lysosomal storage disorder characterized by the accumulation of cholesterol and glycolipids within lysosomes. This is due to a defect in the protein needed to transport cholesterol out of lysosomes. The other options are not associated with this disease.

Question 7

The three-legged assembly of protein chains that makes up a clathrin molecule and that can assemble into a network of polygons resembling a honeycomb is called a _____.
A)trigeminy
B)triskeleton
C)trigellium
D)triskelion
E)triskellium

Accepted Answer

The word "triskelion" comes from Greek roots meaning "three-legged." The clathrin protein chains assemble into a three-legged structure called a triskelion, which can then assemble into a honeycomb-like network of polygons.

Question 8

How many subcompartments do peroxisomes have into which an imported protein can be placed?
A)1
B)2
C)3
D)4

Accepted Answer

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

Question 9

The best-studied adaptors that participate in the formation of the coated pits and coated vesicles of clathrin-mediated endocytosis are the _____ adaptors.
A)COPII
B)GGA
C)AP2
D)clathrin
E)COPI

Accepted Answer

The adaptors that participate in the formation of coated pits and coated vesicles of clathrin-mediated endocytosis are the AP2 adaptors. They are responsible for selecting and binding to cargo molecules, as well as to clathrin molecules, to initiate the formation of the coated pit. The other options, COPII, GGA, clathrin, and COPI, are involved in other types of vesicle formation and trafficking pathways.

Question 10

Which of the following organelles import(s)proteins through one or more outer boundary membranes?
A)the nucleus
B)mitochondria
C)chloroplasts
D)peroxisomes
E)all of these are correct

Accepted Answer

All of these organelles (the nucleus, mitochondria, chloroplasts, and peroxisomes) import proteins through one or more outer boundary membranes. Proteins are synthesized in the cytosol and must be imported into these organelles to perform their specific functions.

Question 11

Which endosomes are typically located in the more interior part of the cell, near the nucleus?
A)late endosomes
B)early endosomes
C)medial lysosomes
D)medial endosomes
E)intellosomes

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 12

What recognizes ubiquitinated signaling receptors and sorts them into the membranes that give rise to the internal vesicles of the late endosomes?
A)ESCRT complexes
B)CREST complexes
C)ESCORT complexes
D)RESCT complexes
E)lysosomes

Accepted Answer

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

Question 13

Which molecules do the AP2 adaptors of the clathrin coat connect?
A)GGA adaptors and clathrin molecules
B)the cytoplasmic tails of specific membrane receptors and clathrin molecules
C)the luminal tails of specific membrane receptors and clathrin molecules
D)the clathrin molecules and cargo molecules
E)cargo molecules and the cytoplasmic tails of specific membrane receptors

Accepted Answer

The answer of Which molecules do the AP2 adaptors of...

Question 14

Where does the peroxisomal targeting signal (PTS)receptor bind to peroxisome-destined proteins?
A)in the nucleus
B)in the cytoplasm (cytosol)
C)in the mitochondrion
D)in the peroxisome
E)in the RER

Accepted Answer

The peroxisomal targeting signal (PTS) receptor binds to peroxisome-destined proteins in the cytoplasm (cytosol) before transporting them into the peroxisome.

Question 15

Which of the following is a mitochondrial subcompartment into which proteins can be delivered?
A)outer mitochondrial membrane (OMM)
B)inner mitochondrial membrane (IMM)
C)intermembrane space
D)matrix
E)all of these are correct

Accepted Answer

All of the choices listed (outer mitochondrial membrane, inner mitochondrial membrane, intermembrane space, and matrix) are subcompartments within the mitochondria that proteins can be delivered to.

Question 16

Drugs that lower blood LDL levels are referred to as _______.
A)olefins
B)statins
C)ancestrins
D)cholestrins
E)cholestrans

Accepted Answer

The drugs that lower blood LDL levels are called statins. Options A and C are not related to cholesterol or lipid-lowering drugs. Options D and E are not actual terms used for cholesterol-lowering drugs.

Question 17

Which of the following organelles imports proteins in their native, folded conformation?
A)mitochondria
B)chloroplasts
C)peroxisomes
D)nuclei
E)lysosomes

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 18

What helps to give different membrane compartments their own unique surface identity?
A)the different proteins contained within them
B)the different surface nucleotides in each one
C)the different shapes of the different membrane compartments
D)the degree of concentration of the contents of the membrane compartments

Accepted Answer

The different proteins contained within membrane compartments help to give them their unique surface identity. Different membrane compartments contain different types of proteins, which are responsible for various functions and interactions with other cells and molecules. These proteins help to define the surface identity of each compartment and differentiate them from one another. Surface nucleotides, shapes, and concentration of contents do not have as significant role in defining membrane compartment identity.

Question 19

The drugs that lower LDL concentration in the blood function by ________.
A)blocking a key cholesterol-degrading enzyme, HMG CoA reductase
B)activating a key cholesterol-degrading enzyme, HMG CoA reductase
C)blocking a key cholesterol synthesis enzyme, HMG CoA reductase
D)activating a key cholesterol synthesis enzyme, HMG CoA reductase
E)blocking a key cholesterol synthesis enzyme, HMG CoA oxidase

Accepted Answer

Drugs that lower LDL concentration in the blood function by blocking a key cholesterol synthesis enzyme, HMG CoA reductase. This enzyme is responsible for catalyzing the rate-limiting step in cholesterol biosynthesis, so inhibiting it leads to a decrease in cholesterol production and subsequently, a decrease in LDL concentration. This class of drugs is commonly referred to as statins.

Question 20

Which molecule below is a GTP-binding protein that is required for the release of a clathrin-coated vesicle from the membrane on which it was formed?
A)AP2
B)GGA
C)clathrin
D)dynamin
E)opsonin

Accepted Answer

Dynamin is a GTP-binding protein that is required for the release of a clathrin-coated vesicle from the membrane on which it was formed. AP2 and GGA are adaptor proteins that help to recruit cargo into clathrin-coated vesicles. Clathrin is a structural protein that forms the lattice structure of the vesicle. Opsonin is a type of protein that helps to tag pathogens for phagocytosis by immune cells.

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

The inner leaflet of the plasma membrane contains elevated levels of _____, which plays an important role in the recruitment of proteins involved in clathrin-mediated endocytosis, like dynamin and AP2.

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

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

Which of the differences between early and late endosomes outlined below is NOT correct?

What protein is associated with HDL particles?

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

The three-legged assembly of protein chains that makes up a clathrin molecule and that can assemble into a network of polygons resembling a honeycomb is called a _____.

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

The best-studied adaptors that participate in the formation of the coated pits and coated vesicles of clathrin-mediated endocytosis are the _____ adaptors.

Which of the following organelles import(s) proteins through one or more outer boundary membranes?

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

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

Which molecules do the AP2 adaptors of the clathrin coat connect?

Where does the peroxisomal targeting signal (PTS) receptor bind to peroxisome-destined proteins?

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

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

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

What helps to give different membrane compartments their own unique surface identity?

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

Which molecule below is a GTP-binding protein that is required for the release of a clathrin-coated vesicle from the membrane on which it was formed?