Question 1

During the translation of mRNA molecules, the new polypeptides are often directed to specific parts of the cell by the presence or absence of short sequences of amino acids called signal peptides. Which of the following would you expect to find in the polypeptides that will eventually fold to become ribosomal proteins?
A)no signal peptide
B)an amino terminal signal peptide
C)an internal signal peptide
D)a signal anchor peptide

Accepted Answer

Ribosomal proteins are synthesized and remain in the cytoplasm, so they do not require a signal peptide to direct them to a specific part of the cell. Therefore, they are expected to have no signal peptide.

Question 2

RNA molecules are transported from the nucleus to the cytoplasm in eukaryotes through:
A)sodium-potassium pumps.
B)aquaporins.
C)passive diffusion.
D)budding off of the nuclear envelope.
E)nuclear pores.

Accepted Answer

RNA molecules are transported from the nucleus to the cytoplasm through nuclear pores, which are large and allow for the passage of molecules up to a certain size. The other options listed do not play a role in RNA transport.

Question 3

During the translation of mRNA molecules, the new polypeptides are often directed to specific parts of the cell by the presence or absence of short sequences of amino acids called signal peptides. Which of the following would you expect to find in the polypeptide that will eventually fold to become a histone protein?
A)no signal peptide
B)an amino terminal signal peptide
C)an internal signal peptide
D)a signal anchor peptide

Accepted Answer

The answer of During the translation of mRNA molecules, the...

Question 4

You notice in your experimental system that a particular protein is no longer entering the nucleus. What could have happened?
A)The signal sequence might be mutated.
B)The chaperone protein might have taken it to a different location.
C)The solute concentration might be higher inside the nucleus.
D)None of the other answer options is correct.

Accepted Answer

The signal sequence is responsible for directing the protein to the nucleus. If it is mutated or absent, the protein will not be able to enter the nucleus.

Question 5

If a mutation rendered the signal recognition particle receptor nonfunctional such that it is no longer able to dissociate from the SRP, what would be the most obvious effect on the cell?
A)Translation of most proteins would be incomplete.
B)All proteins normally secreted by the cell would remain partially formed and attached to the endoplasmic reticulum.
C)Proteins destined for the nucleus would remain in the cytosol.
D)No proteins would arrive at their proper destinations within the cell.
E)All proteins normally secreted by the cell would remain in the cytosol.

Accepted Answer

The signal recognition particle receptor is responsible for recognizing the signal peptide on nascent polypeptides and directing them to the endoplasmic reticulum for secretion or membrane insertion. If the receptor is nonfunctional and unable to dissociate from the signal recognition particle, the protein would not be properly targeted to the endoplasmic reticulum and would remain partially formed and attached to the membrane, leading to the accumulation of misfolded proteins and potential cellular dysfunction. This would primarily affect proteins intended for secretion, hence option B is the correct answer.

Question 6

With which of the following is a signal-recognition particle (SRP) capable of interacting?
A)an SRP receptor
B)a ribosome
C)a signal sequence in a protein destined for the ER

Accepted Answer

The answer of With which of the following is a...

Question 7

In a eukaryotic cell, how does mRNA get out of the nucleus?
A)diffusion
B)through nuclear pores
C)through the endoplasmic reticulum
D)through the Golgi apparatus

Accepted Answer

mRNA molecules are too large to diffuse through the nuclear envelope. Instead, they are transported through nuclear pores, which allow for selective passage of molecules in and out of the nucleus.

Question 8

Which of the following are processed in the Golgi apparatus?
A)integral membrane proteins of the plasma membrane
B)proteins that are secreted from the cell
C)proteins that will be broken down by lysosomes
D)mRNA molecules for the removal of introns
E)enzymes required for the synthesis of phospholipids

Accepted Answer

The Golgi apparatus processes and modifies proteins that are destined for the plasma membrane (A), secretion (B), or lysosomes (C). It does not process mRNA (D) or synthesize phospholipids (E).

Question 9

Which one of the following cellular compartments does NOT have a double membrane structure separating it from the rest of the cell?
A)lysosomes
B)the nucleus
C)mitochondria

Accepted Answer

Lysosomes have a single membrane, while both the nucleus and mitochondria have a double membrane structure.

Question 10

You are investigating a particular cell type, and you notice that a protein normally found in the lysosome ends up being secreted out of the cell. This appears to be the only thing wrong with these cells. Suggest a defect that could explain this observation.

Accepted Answer

The answer of You are investigating a particular cell type,...

Question 11

During the translation of mRNA molecules, the new polypeptides are often directed to specific parts of the cell by the presence or absence of short sequences of amino acids called signal peptides. Which of the following would you expect to find in the polypeptides that will eventually fold to become enzymes important in photosynthesis, such as NADP⁺ reductase? A)no signal peptide B)an amino terminal signal peptide C)an internal signal peptide D)a signal anchor peptide

Accepted Answer

Enzymes important in photosynthesis, such as NADP reductase, are typically located in the chloroplast. To direct these newly synthesized polypeptides to the chloroplast, they often contain an amino terminal signal peptide. This signal peptide guides the polypeptide to the chloroplast where it is then imported and the signal peptide is cleaved off.

Question 12

When physicians perform organ transplants, they make sure that there is a match between the donor (the person donating the organ) and the recipient (the person receiving the organ). What feature of the cell is being matched?
A)phospholipids in the plasma membrane
B)cholesterol in the plasma membrane
C)protein channels in the plasma membrane
D)proteins pumps in the plasma membrane
E)glycyoproteins in the plasma membrane

Accepted Answer

The feature being matched is the glycoproteins in the plasma membrane. These molecules play a crucial role in cell recognition and immune response, making them essential for compatibility in organ transplants to avoid rejection.

Question 13

A transmembrane protein in the outer membrane of the nuclear envelope would LEAST likely be found later in which one of the following cellular locations?
A)the plasma membrane
B)a lysosomal membrane
C)a mitochondrial membrane
D)the Golgi apparatus membrane
E)the rough endoplasmic reticulum membrane

Accepted Answer

A transmembrane protein in the outer membrane of the nuclear envelope is specific to the nucleus and is not found in other organelles. Lysosomes (B), mitochondria (C), Golgi apparatus (D), and rough endoplasmic reticulum (E) are all membrane-bound organelles that are separate from the nucleus and would not have this specific transmembrane protein present. However, plasma membranes (A) are also composed of phospholipid bilayers, similar to the nuclear envelope, and some transmembrane proteins could potentially be present in both locations.

Question 14

A protein with an internal signal sequence is MOST likely to be located in:
A)the nucleus.
B)a mitochondrion.
C)the cytoplasm.
D)a chloroplast.
E)the extracellular space.

Accepted Answer

An internal signal sequence typically directs a protein to the nucleus, where it can function in processes such as DNA replication and transcription.

Question 15

The signal recognition particle and its receptor on the surface of the endoplasmic reticulum ensure that proteins destined for incorporation into cellular membranes or for export from the cell are translated into the endoplasmic reticulum so that they may be processed through the endomembrane system. If a mutation rendered the signal recognition particle receptor nonfunctional such that the receptor was no longer able to dissociate from the SRP, what would be the most obvious effect on the cell?

Accepted Answer

The answer of The signal recognition particle and its receptor...

Question 16

Which of the following would be synthesized in and processed by the rough endoplasmic reticulum and Golgi apparatus?
A)fatty acids and phospholipids
B)DNA polymerase and RNA polymerase
C)lysosomal enzymes
D)cytoskeletal proteins, actin and tubulin, which are found in the cytoplasm

Accepted Answer

Lysosomal enzymes are synthesized in rough endoplasmic reticulum and then processed in the Golgi apparatus before being transported to lysosomes. Fatty acids and phospholipids can also be synthesized in the ER and Golgi, but not necessarily processed by the Golgi. DNA and RNA polymerases are not synthesized by the ER and Golgi. Cytoskeletal proteins are synthesized in free ribosomes in the cytoplasm, not in the ER or Golgi.

Question 17

Insulin is a protein hormone that helps to control the level of glucose in the blood. It is secreted from specialized cells in the pancreas. Based on this information, which path does insulin take out of the cell?
A)ER membrane $\rightarrow$  vesicle membrane $\rightarrow$  plasma membrane $\rightarrow$ exterior of cell
B)vesicle $\rightarrow$  ER $\rightarrow$  Golgi apparatus$\rightarrow$  exterior of cell
C)nucleus $\rightarrow$ ER $\rightarrow$  Golgi apparatus $\rightarrow$  vesicle $\rightarrow$  exterior of cell
D)ER $\rightarrow$  Golgi apparatus $\rightarrow$  vesicle $\rightarrow$  exterior of cell
E)ER $\rightarrow$  nucleus $\rightarrow$  cytosol $\rightarrow$ exterior of cell

Accepted Answer

Insulin is synthesized in the rough endoplasmic reticulum (ER), processed in the Golgi apparatus, and packaged into vesicles for secretion outside the cell. Therefore, insulin travels from the ER to the Golgi apparatus to a vesicle, and finally is secreted to the exterior of the cell. Choice D is the only option that follows this path.

Question 18

Which one of the following is moved from one side of a lysosomal membrane to the other by a transport protein in the lysosomal membrane?
A)protons
B)broken-down macromolecules
C)enzymes capable of breaking down macromolecules being delivered from the Golgi apparatus
D)protons and broken-down macromolecules

Accepted Answer

The answer of Which one of the following is moved...

Question 19

During the translation of mRNA molecules, the new polypeptides are often directed to specific parts of the cell by the presence or absence of short sequences of amino acids called signal peptides. Which of the following would you expect to find in the polypeptide that will eventually fold to become an ion channel protein?
A)no signal peptide
B)an amino terminal signal peptide
C)an internal signal peptide
D)a signal anchor peptide

Accepted Answer

Ion channel proteins are membrane proteins that span the lipid bilayer of the cell membrane. Therefore, it is likely that they would have a signal anchor peptide, which is a type of signal sequence that directs proteins to the cell membrane.

Question 20

You are investigating a particular cell type, and you notice that a protein normally found in the lysosome ends up being secreted from the cell. This appears to be the only thing wrong with these cells. Of the following conditions, which is the MOST likely cause of this defect in these cells?
A)The lysosome leaks the protein out of the cell.
B)One of the signal sequences on the lysosomal protein is defective.
C)Transport vesicles responsible for sorting in the cell are defective.
D)The pH of the lysosome is not low enough for the protein to remain in it.

Accepted Answer

Lysosomal proteins have signal sequences that direct them to the lysosome for sorting and eventual degradation. If one of these signal sequences is defective, the protein may not be properly sorted and could end up being secreted from the cell. The other options (A, C, and D) do not directly relate to the lysosomal sorting mechanism and are less likely to cause this specific defect.

Quiz 5: Organizing Principles: Lipids, Membranes, and Cell Compartments

RNA molecules are transported from the nucleus to the cytoplasm in eukaryotes through:

You notice in your experimental system that a particular protein is no longer entering the nucleus. What could have happened?

If a mutation rendered the signal recognition particle receptor nonfunctional such that it is no longer able to dissociate from the SRP, what would be the most obvious effect on the cell?

With which of the following is a signal-recognition particle (SRP) capable of interacting?

In a eukaryotic cell, how does mRNA get out of the nucleus?

Which of the following are processed in the Golgi apparatus?

Which one of the following cellular compartments does NOT have a double membrane structure separating it from the rest of the cell?

You are investigating a particular cell type, and you notice that a protein normally found in the lysosome ends up being secreted out of the cell. This appears to be the only thing wrong with these cells. Suggest a defect that could explain this observation.

When physicians perform organ transplants, they make sure that there is a match between the donor (the person donating the organ) and the recipient (the person receiving the organ) . What feature of the cell is being matched?

A transmembrane protein in the outer membrane of the nuclear envelope would LEAST likely be found later in which one of the following cellular locations?

A protein with an internal signal sequence is MOST likely to be located in:

Which of the following would be synthesized in and processed by the rough endoplasmic reticulum and Golgi apparatus?

Insulin is a protein hormone that helps to control the level of glucose in the blood. It is secreted from specialized cells in the pancreas. Based on this information, which path does insulin take out of the cell?

Which one of the following is moved from one side of a lysosomal membrane to the other by a transport protein in the lysosomal membrane?

You are investigating a particular cell type, and you notice that a protein normally found in the lysosome ends up being secreted from the cell. This appears to be the only thing wrong with these cells. Of the following conditions, which is the MOST likely cause of this defect in these cells?