Question 1

In MDCK cells,which of the following is a sorting signal that allows proteins to be targeted to the apical membrane?

Accepted Answer

GPI anchors are used to target proteins to the apical membrane in polarized cells like MDCK cells.

Question 2

Which portion of a clathrin coat recognizes internalization signals such as Leu-Leu,Asn-Pro-X-Tyr,and Tyr-X-X- in the cytosolic domain of cell-surface endocytic receptors?

Accepted Answer

The answer of Which portion of a clathrin coat recognizes...

Question 3

How are soluble,luminal ER proteins that "leak" out of the ER retrieved to the ER?

Accepted Answer

The answer of How are soluble,luminal ER proteins that "leak"...

Question 4

Which of the following is TRUE about lysosomes?

Accepted Answer

The answer of Which of the following is TRUE about...

Question 5

Acidification of endosomes is important in dissociating:

Accepted Answer

Acidification of endosomes is crucial for the release of iron from transferrin, allowing iron to be utilized by the cell.

Question 6

Lipoproteins are effective in transporting lipid molecules in an aqueous environment because their surface layer is:

Accepted Answer

Lipoproteins have an amphipathic surface layer, meaning that it has both hydrophobic and hydrophilic properties. This allows it to effectively transport lipid molecules, which are generally hydrophobic, in an aqueous environment. Glycosidic bonds are not typically found in lipoprotein surface layers.

Question 7

An important molecule for generating fatty acids in the cell enters via receptor-mediated endocytosis.The complex formed between the receptor on the plasma membrane and the important molecule is stable only at neutral pH.Based on this knowledge,you would predict:

Accepted Answer

The answer of An important molecule for generating fatty acids...

Question 8

Describe the types of mutations in the LDL receptor that would cause familial hypercholesterolemia.

Accepted Answer

The answer of Describe the types of mutations in the...

Question 9

In hepatocytes,the process by which apically destined proteins travel from the basolateral region across the cell before fusing with the apical membrane is called:

Accepted Answer

This process is specifically known as transcytosis, which involves the transport of molecules from one side of the cell to the other side. Exocytosis is the process by which molecules exit the cell, and endocytosis is the process by which molecules enter the cell. Neither of these processes accurately describes the transport of apically destined proteins across hepatocytes.

Question 10

Formation of the late endosome/multivesicular endosome occurs by mechanisms similar to those of:

Accepted Answer

The formation of late endosomes/multivesicular endosomes involves the inward budding of the endosomal membrane to form intraluminal vesicles, a process that is mechanistically similar to the budding of retroviruses from the plasma membrane.

Question 11

What is autophagy?

Accepted Answer

The answer of What is autophagy?...

Question 12

The mannose 6-phosphate residue is important,as it is required to target soluble enzymes to the__________.The two enzymes responsible for attaching this residue onto these soluble enzymes reside in the ____________.

Accepted Answer

The mannose 6-phosphate residue is required to target soluble enzymes to the lysosome. The two enzymes responsible for attaching this residue onto these soluble enzymes reside in the cis-Golgi.

Question 13

The LDL receptor is a receptor for:

Accepted Answer

The LDL receptor is responsible for both binding to and internalizing low-density lipoprotein (LDL) as well as recognizing apolipoprotein B, which is a component of LDL. Therefore, the best choice is D (apolipoprotein B and receptor-mediated endocytosis of LDL).

Question 14

The topogenic sequence of transferrin must include:

Accepted Answer

The topogenic sequence of transferrin includes an internal signal-anchor sequence with positive charges N-terminal to the SA. This is important for the insertion of the protein into the ER membrane. There is no mention of a signal sequence, stop-transfer sequences, or alternating signal-anchor sequences in relation to the topogenic sequence of transferrin.

Question 15

Protein sorting of anterograde cargo to different destinations within the Golgi complex occurs in the:

Accepted Answer

The trans-Golgi network (TGN) is the key sorting station in the Golgi apparatus, where proteins are sorted and dispatched to their final destinations, including lysosomes, the plasma membrane, or secretion.

Question 16

Professor George Palade's elegant experiment to follow protein synthesis and trafficking,published nearly 60 years ago,provided us with a great deal of information and has been used as a tool by several investigators.If you had access to all the reagents needed to repeat the in vitro experiment,describe what you would need to do to see the progression of newly synthesized proteins and their transport in the cell.

Accepted Answer

The answer of Professor George Palade's elegant experiment to follow...

Question 17

The mannose 6-phosphate residue is important,as it is required to target soluble enzymes to the lysosome.The two enzymes responsible for attaching this residue onto these soluble enzymes reside in the:

Accepted Answer

The enzymes responsible for attaching mannose 6-phosphate residues to lysosomal enzymes are located in the cis-Golgi network.

Question 18

How are clathrin-coated vesicles pinched off?

Accepted Answer

The answer of How are clathrin-coated vesicles pinched off?...

Question 19

Receptor-mediated endocytosis of iron-carrying transferrin results in:

Accepted Answer

The answer of Receptor-mediated endocytosis of iron-carrying transferrin results in:
...

Quiz 13: Vesicular Traffic, Secretion, and Endocytosis