Question 1

Which molecule type is thought to direct the movement of vesicles through the cytoplasm to their final destination?

Accepted Answer

Microtubules are part of the cytoskeleton and are responsible for intracellular transport, including the movement of vesicles. Microfilaments, intermediate filaments, collagen, and keratin are also part of the cytoskeleton but are not primarily involved in vesicle transport.

Question 2

Which techniques are currently used to harvest extracellular vesicles for use in drug delivery research? (Select all correct choices)

Accepted Answer

The answer of Which techniques are currently used to harvest...

Question 3

When Rabs have bound to GTP, what do they do?

Accepted Answer

When Rabs have bound to GTP, they recruit specific cytosolic tethering proteins to specific membrane surfaces. This helps to ensure that the correct vesicle is targeted to the correct membrane for fusion to occur.

Question 4

Which of these molecules is NOT transported in extracellular vesicles?

Accepted Answer

DNA is too large to be transported in extracellular vesicles, which typically have a size limit of around 100-150 nm. The other molecules listed (cytoplasmic proteins, membrane proteins, mRNA, and noncoding RNA) can be transported in extracellular vesicles.

Question 5

A ____________ is thought to dissociate the 4-stranded SNARE complex by attaching to the SNARE bundle and, using energy from ATP hydrolysis, twisting it apart.

Accepted Answer

The doughnut-shaped, cytosolic protein called NSF is known to dissociate the 4-stranded SNARE complex by attaching to the SNARE bundle and using energy from ATP hydrolysis to twist it apart. ARF1 and Rab are not associated with SNARE complex dissociation, and NSF is shaped like a doughnut, not a cylinder.

Question 6

What acts as an address directing lysosomal enzymes to lysosomes?

Accepted Answer

Mannose-6-phosphate (M6P) residues on lysosomal enzymes act as an address directing them to lysosomes. These enzymes are synthesized in the rough endoplasmic reticulum with M6P residues added to them. The M6P residues bind to M6P receptors on the surface of the trans-Golgi network, where they are packaged into vesicles for transport to lysosomes. Once inside the lysosome, the low pH environment causes dissociation of the enzyme-receptor complex, allowing the enzyme to be delivered to its target.

Question 7

Why does glucocerebrosidase taken into macrophages by receptor-mediated endocytosis end up in lysosomes?

Accepted Answer

Lysosomes are the natural target for endocytosed macromolecules and enzymes in macrophages. Once inside the macrophage, glucocerebrosidase will be targeted to lysosomes for degradation or recycling.

Question 8

Where is this common domain of SNAREs located, of what is it composed and what is it called?

Accepted Answer

The common domain of SNAREs is located in the cytosol and is composed of 60-70 amino acids that form a complex with another SNARE motif. This domain is called the SNARE coil or SNARE motif.

Question 9

Lysosomal enzymes are transported from the TGN in vesicles coated with what protein?

Accepted Answer

Lysosomal enzymes are transported from the TGN to the lysosomes in vesicles coated with clathrin protein. Clathrin-mediated transport is a process by which vesicles bud from a donor membrane and move to their destination membrane, using clathrin triskelia as the coat proteins.

Question 10

What happens to the clathrin coat once the vesicle has budded from the Golgi body?

Accepted Answer

The clathrin coat is lost once the vesicle has budded from the Golgi body. The coat is shed and recycled back to the cytosol, leaving the vesicle free to move to its target destination.

Question 11

What would happen to the movement of vesicles toward their eventual target if a microtubule inhibitor like colchicine were added to the cells?

Accepted Answer

Colchicine inhibits microtubule polymerization by binding to the tubulin subunits. Since microtubules play a critical role in vesicle transport, adding colchicine would slow down or stop vesicle movement towards their target.

Question 12

Treatment of lysosomal storage diseases with enzyme replacement therapy involves _______.

Accepted Answer

Enzyme replacement therapy involves sending functional copies of the missing enzyme to the precise cell sites where the deficiency is manifested in order to alleviate the symptoms and slow the progression of the disease. This allows the deficient cells to carry out their normal functions and reduce the accumulation of substrates. Targeting mutant copies of the missing enzyme or administering drugs to inhibit the synthesis of substances that accumulate in the disease are not part of enzyme replacement therapy.

Question 13

Synaptic vesicle fusion to the presynaptic membrane in a neuron is regulated by what calcium-binding protein found in the membrane of the synaptic vesicle?

Accepted Answer

Synaptic vesicle fusion to the presynaptic membrane is regulated by synaptotagmin, which is a calcium-binding protein found in the membrane of the synaptic vesicle.

Question 14

I-cell disease is typified by __________.

Accepted Answer

I-cell disease is characterized by all of the mentioned features: lysosomes filled with undegraded materials due to the improper targeting of lysosomal enzymes, which are normally marked by mannose 6-phosphate residues for lysosomal delivery. The deficiency in N-acetylglucosamine phosphotransferase is the underlying cause, leading to the enzymes being secreted outside the cell instead of being directed to the lysosomes.

Question 15

How do Rabs associate with membranes?

Accepted Answer

Rabs associate with membranes via a lipid anchor, specifically a prenylated cysteine residue. This anchor allows them to interact with specific membrane regions and participate in vesicle trafficking.

Question 16

You are working on a project in which you block autophagy in a particular portion of the brain of a laboratory animal. What happens to these animals? (Select all correct choices)

Accepted Answer

Autophagy is the process by which cells break down and recycle their own components, including organelles and proteins. Blocking autophagy in nerve cells can lead to accumulation of damaged organelles and proteins, causing continuous damage to the cells. Over time, this can lead to a massive loss of nerve cells in the targeted region of the brain. Therefore, choices B and D are correct, while choices A and C are incorrect.

Question 17

V-SNAREs are found _______________and t-SNARES are found _________________:

Accepted Answer

V-SNAREs are incorporated into the transport vesicle membrane during budding, while t-SNAREs are found in the target compartment membrane. Therefore, choice A correctly describes the location of each type of SNARE.

Question 18

What are the two functional categories of SNAREs?

Accepted Answer

The two functional categories of SNAREs are v-SNAREs, which are located on vesicles, and t-SNAREs, which are located on target membranes. Therefore, the best choice is C, which lists these two categories. Option A is incorrect because there is no such thing as a "g-SNARE." Option B is incorrect because there is no such thing as a "t-SNARE." Option D is incorrect because there is no such thing as an "er-SNARE." Option E is incorrect because there is no such thing as a "g-SNARE."

Question 19

In general, diseases that result from a deficiency of a single lysosomal enzyme are called ________.

Accepted Answer

Diseases resulting from a deficiency of a single lysosomal enzyme are known as lysosomal storage disorders. This is due to the fact that substrates accumulate in the lysosomes as a result of the enzyme deficiency, causing a variety of symptoms and complications. Tay-Sachs disease is a specific example of a lysosomal storage disease caused by a deficiency of the enzyme hexosaminidase A. The other answer choices (A, D, and E) are not commonly used medical terms for these types of disorders.

Question 20

Why does targeting glucocerebrosidase to lysosomes in macrophages serve as a treatment for Gaucher's disease?

Accepted Answer

Gaucher's disease is characterized by a deficiency in the enzyme glucocerebrosidase, which normally breaks down a type of fat called glucocerebroside. This leads to the accumulation of glucocerebroside in lysosomes of macrophages, causing organomegaly, anemia and decreased bone density. Targeting glucocerebrosidase to lysosomes in macrophages is a treatment for Gaucher's disease because it delivers the enzyme to the precise site in the cell where the deficiency is manifested, correcting the deficit. In this way, it helps to reduce the buildup of glucocerebroside in macrophages, alleviating the symptoms of the disease.

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