Cell Bio Chapter 15

Imagine that 32 million histone octamers are required to package the DNA in a human cell. How many histone proteins must pass through each nuclear pore complex per second in a cell that has 3000 nuclear pores and divides once per day? Choose one: a. 1 histone per second b. about 0.1 histones per second (or 1 histone every 10 seconds) c. 2 histones per second d. 3000 histones per secondabout e. 0.5 histones per second (or 1 histone every 2 seconds)

1 histone per second

A macrophage swallows 25% of its own volume of fluid each hour. This means that it removes 3% of its plasma membrane each minute, or 100% in about half an hour.At what rate will this membrane be replaced by exocytosis? Choose one: a. 3% per hour b. 100% per hour c. 50% per hour d. 200% per hour e. 25% per hour

200% per hour

(Q009) Which of the following accurately describes a step in GTP-driven nuclear transport? a. GTP-bound cargo interacts specifically with the protein fibrils of the pore b. Binding of Ran-GTP to the receptor releases the cargo protein c. GTP hydrolysis powers a membrane-bound transporter protein d. Ran-GDP escorts the nuclear receptor back to the cytosol

Binding of Ran-GTP to the receptor releases the cargo protein

Which of the following accurately describes a step in GTP-driven nuclear transport? Choose one: A. GTP-bound cargo interacts specifically with the protein fibrils of the pore. B. Binding of Ran-GTP to the receptor releases the cargo protein. C. Ran-GDP escorts the nuclear receptor back to the cytosol. D. GTP hydrolysis powers a membrane-bound transporter protein.

Binding of Ran-GTP to the receptor releases the cargo protein.

(Q013) How do clathrin-coated vesicles select their cargo molecules? a. Cargo receptors bind specifically to cargo proteins and to clathrin b. Cargo is selected randomly and is sorted later in the endosomes c. Cargo is actively transported into preformed clathrin-coated vesicles d. Specific cargo molecules have a high affinity for clathrin

Cargo receptors bind specifically to cargo proteins and to clathrin

Researchers studying yeast discovered that, for some mutants, when the temperature at which the cells are grown is elevated from 25ºC to 37ºC, their secretory pathway no longer functions and the cells grow dense with unsecreted protein.When these cells are examined microscopically, they can be divided into groups that vary in terms of where the unsecreted proteins accumulate. In some of the mutants, proteins accumulate in the ER; in others, the Golgi; in others, they accumulate in vesicles near the plasma membrane.What is the likely explanation for this difference in appearance? Choose one: a. The temperature-sensitive mutant proteins accumulate in different compartments. b. Different temperature-sensitive mutations disrupt protein synthesis. c. Different temperature-sensitive mutations promote an increase in protein synthesis. d. Different temperature-sensitive mutations disrupt the integrity of cell membranes. e. Different temperature-sensitive mutations affect different stages of the transport process.

Different temperature-sensitive mutations affect different stages of the transport process.

(Q006) What would the final destination be for a protein bearing both an ER sorting signal and a nuclear localization signal? a. ER b. nucleus c. Golgi d. cytoplasm

ER

What would be the effect on cell function of inhibiting phosphorylation of eIF2? Choose one: A. The chaperones would be activated in response to cell stress. B. The ribosome would be less active. C. More proteins would be synthesized in order to respond to cell stress. D. Translation would not be inhibited in response to cell stress.

Translation would not be inhibited in response to cell stress.

Which is not a function of proteins? Choose one: A. encasing certain viruses B. encoding genetic information C. providing cells with structural support D. catalyzing biochemical reactions E. acting as molecular motors

encoding genetic information

What would the final destination be for a protein bearing both an ER sorting signal and a nuclear localization signal? Choose one: A. nucleus B. Golgi apparatus C. endoplasmic reticulum D. cytoplasm

endoplasmic reticulum

(Q015) Which of the following is a covalent modification that occurs mainly in the ER? a. addition of phosphate group b. maturation of oligosaccharide chains c. methylation of side chains d. formation of disulfide bonds

formation of disulfide bonds

Which of the following components of receptor-mediated endocytosis of LDL is incorrectly matched with its function?Choose one: A. adaptin: binds to the specific receptors and recruits clathrin B. clathrin: forms the coated vesicle C. LDL receptors: form bridges between the LDL particle and adaptin D. lysosome: releases LDL from the receptor

lysosome: releases LDL from the receptor

(Q004) Which of the following organelles is NOT a part of the endomembrane system? a. lysosomes b. nucleus c. Golgi d. ER

nucleus

(Q007) Fully folded proteins can be transported into which of the following organelles? a. nucleus b. mitochondrion c. ER d. chloroplasts

nucleus

(Q005) Which of the following compartments receives proteins directly from cytosol? a. endosomes b. peroxisomes c. lysosomes d. Golgi

peroxisomes

(Q018) Which of the endocytic pathways involves the ingestion of large particles or microorganisms and is performed mainly by specialized cells? a. phagocytosis b. exocytosis c. pinocytosis d. receptor-mediated endocytosis

phagocytosis

(Q0019) Which of the following pathways helps selectively concentrate substances to be ingested by their binding to proteins on the cell surface? a. receptor-mediated endocytosis b. exocytosis c. pinocytosis d. phagocytosis

receptor-mediated endocytosis

(Q020) Lysosomes contain ____________ that can break down diverse macromolecules, cell parts, and microorganisms a. hydrolytic b. biosynthetic c. isomerase d. kinase

hydrolytic

(Q008) Nuclear pores restrict larger molecules from traversing the membrane due to their: a. very small pore size b. hydrophobic interior c. double membrane d. interwoven meshwork of protein fibrils

interwoven meshwork of protein fibrils

In a typical human secretory cell, which of the following membranes has the largest surface area?Choose one: a. plasma membrane b. smooth ER c. nuclear inner membrane d. rough ER e. lysosome

rough Er

In muscle cells, which organelle sequesters Ca2+ from the cytosol?Choose one: a. endosome b. smooth ER c. mitochondrion d. rough ER e. lysosome

smooth ER

(Q001) Which of the following organelles is the site of steroid hormone synthesis in endocrine cells? a. cytosol b. mitochondrion c. nucleus d. smooth endoplasmic reticulum

smooth endoplasmic reticulum

Which statements are true regarding protein transport into peroxisomes? Choose one or more: -Like mitochondria, peroxisomes contain translocators through which proteins enter the organelle. -Like prospective nuclear proteins, some peroxisomal proteins are recognized by receptor proteins in the cytosol. -Like mitochondrial proteins, some peroxisomal proteins arrive via vesicles that bud from the ER. -Like proteins transported into the nucleus, proteins must unfold before entering the peroxisome. -Like proteins destined for the ER, nucleus, or mitochondria, peroxisomal proteins bear a distinct signal sequence. -Like proteins transported into mitochondria, proteins can enter the peroxisome in a folded conformation.

-Like mitochondria, peroxisomes contain translocators through which proteins enter the organelle. -Like prospective nuclear proteins, some peroxisomal proteins are recognized by receptor proteins in the cytosol. -Like proteins destined for the ER, nucleus, or mitochondria, peroxisomal proteins bear a distinct signal sequence.

Which of the following statements are true of mitochondrial proteins that are synthesized in the cytosol? Choose one or more: -Proteins cross both the inner and outer mitochondrial membranes as they are imported. -Proteins are unfolded as they are transported into the organelle. -Proteins are transported across the mitochondrial membranes while being synthesized. -Protein transport into mitochondria is powered in part by ATP hydrolysis. -Proteins usually have a signal sequence at their C-terminus. -Chaperone proteins help draw the proteins inside the mitochondrion.

-Proteins cross both the inner and outer mitochondrial membranes as they are imported. -Proteins are unfolded as they are transported into the organelle. -Protein transport into mitochondria is powered in part by ATP hydrolysis. -Chaperone proteins help draw the proteins inside the mitochondrion.

Which statements are true of receptor-mediated endocytosis?Choose one or more: -Internalized endocytic vesicles fuse with lysosomes, which can return empty receptors to the plasma membrane. -It allows hemoglobin to be taken up by immature red blood cells. -The process can be hijacked by viruses to gain entry into cells. -It allows cholesterol-carrying low-density lipoproteins (LDLs) to be taken up by cells. -It allows the internalization of extracellular substances in clathrin-coated vesicles.

-The process can be hijacked by viruses to gain entry into cells. -It allows cholesterol-carrying low-density lipoproteins (LDLs) to be taken up by cells. -It allows the internalization of extracellular substances in clathrin-coated vesicles.

(Q003) Approximately what percentage of the volume of a typical eukaryotic cell is comprised of cytosol? a. 80% b. 50% c. 10% d. 20%

50%

How does a polyribosome differ from the rough ER? Choose one: a. A polyribosome will synthesize only cytosolic proteins. b. A polyribosome will be found only in prokaryotes. c. A polyribosome will not interact with the ER membrane. d. A polyribosome will synthesize a single type of protein. e. A polyribosome will synthesize only soluble proteins.

A polyribosome will synthesize a single type of protein.

Which of the following correctly describe steps required for protein transport into the rough ER? Choose one or more: A. recognition and binding of the protein signal sequence by SRP B. initial transfer of the signal sequence to the inside of the rough ER C. passing of the protein to a protein translocation channel in the ER membrane D. cleavage of the signal sequence from the protein by signal peptidase

A. recognition and binding of the protein signal sequence by SRP C. passing of the protein to a protein translocation channel in the ER membrane D. cleavage of the signal sequence from the protein by signal peptidase

Many viruses enter cells through receptor-mediated endocytosis. Which of the following strategies could be affective in blocking entry of this class of viruses into cells and could be used to treat viral infections?Choose one or more: A.Block the receptor with an antibody. B.Block the actin filaments. C.Block the function of adaptin. D.Increase the activity of clathrin.

A.Block the receptor with an antibody. C.Block the function of adaptin.

Which of the following is a role of the oligosaccharides on glycosylated proteins? Choose one or more: A.promoting cell-cell recognition B.protecting the protein from degradation and holding it in the ER until it is properly folded C.serving as a transport signal for packaging the protein into appropriate transport vesicles D.acting as a signal sequence for proteins destined to remain in the cytosol E.providing a source of energy for the cell F.forming part of the cell's glycocalyx, or carbohydrate layer

A.promoting cell-cell recognition B.protecting the protein from degradation and holding it in the ER until it is properly folded C.serving as a transport signal for packaging the protein into appropriate transport vesicles F.forming part of the cell's glycocalyx, or carbohydrate layer

Three separate pathways make up the unfolded protein response in the ER. Sort the following characteristics of the unfolded protein responses into the correct pathway. All Three Pathways IRE! Pathway Only PERK Pathway Only ATF6 Pathway Only

All Three Pathways: -Activates transcription of specific genes -Increases the ability of the ER to fold more proteins IRE! Pathway Only: -Leads to removal of an intron from a specific RNA and translation of the mRNA -Contains both kinase and RNAse domains PERK Pathway Only: -Phosphorylates a translation initiation factor, leading to a global reduction in translation ATF6 Pathway Only: -Requires cleavage of the protein -Travels to the Golgi apparatus and the nucleus before activating transcription

(Q002) Which of the following organelles is surrounded by a single membrane? a. chloroplasts b. Golgi apparatus c. mitochondria d. nucleus

Golgi apparatus

ATP is important for chaperone protein function. Why would protein import into mitochondria be disrupted if ATP were depleted from inside mitochondria? Choose one: A. The signal sequence would not be recognized on the mitochondrial protein. B. The translocation apparatus would be unable to function without ATP hydrolysis. C. The protein could slip back out of the mitochondria during transport. D. The protein would be blocked from entering the translocation apparatus.

C. The protein could slip back out of the mitochondria during transport.

(Q016) How are misfolded proteins and incompletely assembled proteins retained in the ER? a. Chaperone proteins bind them and prevent their entry into vesicles b. Incompletely assembled proteins aggregate into large complexes that are degraded into the ER c. The misfolded proteins are immediately sent to lysosomes d. Misfolded proteins can exit the ER but are immediately returned by a KDEL sequence

Chaperone proteins bind them and prevent their entry into vesicles

Which best describes a pathway that a protein might follow from synthesis to secretion?Choose one: a. Cytosol → ER → transport vesicle → Golgi apparatus → transport vesicle → plasma membrane b. ER → Golgi apparatus → secretory vesicle → plasma membrane c. ER → Golgi apparatus → transport vesicle → endosome → secretory vesicle → plasma membrane d. Cytosol → ER → Golgi apparatus → transport vesicle → endosome → secretory vesicle → plasma membrane e. Cytosol → ER → secretory vesicle → plasma membrane

Cytosol → ER → transport vesicle → Golgi apparatus → transport vesicle → plasma membrane

Which organelle cannot receive proteins directly from the cytosol?Choose one: a. mitochondrion b. chloroplast c. nucleus d. Golgi apparatus e. peroxisome

Golgi apparatus

(Q012) Which of the following is a difference between exocytic and endocytic pathways? a. Endocytic pathways bring in soluble proteins only, whereas exocytic pathways move both soluble proteins and membrane-bound organelles b. Exocytic pathways utilize transport vesicles, whereas endocytic pathways use only endosomes c. Exocytic pathways often start with synthesis of proteins, whereas endocytic pathways involve breaking down macromolecules like proteins d. Endocytic pathways transfer proteins to the Golgi apparatus, whereas exocytic pathways transfer proteins from the Golgi.

Exocytic pathways often start with synthesis of proteins, whereas endocytic pathways involve breaking down macromolecules like proteins

Which of the following is a difference between exocytic and endocytic pathways?Choose one: A. Endocytic pathways bring in soluble proteins only, whereas exocytic pathways move both soluble proteins and membrane-bound proteins. B. Exocytic pathways often start with synthesis of proteins, whereas endocytic pathways involve breaking down macromolecules like proteins. C. Exocytic pathways utilize transport vesicles, whereas endocytic pathways use only endosomes. D. Endocytic pathways transfer proteins to the Golgi apparatus, whereas exocytic pathways transfer proteins from the Golgi.

Exocytic pathways often start with synthesis of proteins, whereas endocytic pathways involve breaking down macromolecules like proteins.

You complete a further experiment by treating your cells with an RNAse inhibitor and get the results shown in Figure B. Given the results of Figure A and Figure B, what pathway(s) is/are important for this cell line? a. IRE1 b. IRE1 and ATF6 c. ATF6 d. IRE1 and PERK e. PERK

IRE1

The three pathways of the unfolded protein response differ in importance in different cell types, enabling cells to tailor the response to their individual needs. You join a lab that studies the relative importance of the UPR in different cell types. Your advisor gives you a new cell culture and directs you to determine which of the three pathways is the most important for that cell type. You first treat the cells with a kinase inhibitor. Given the results in Figure A, which pathway(s) might be important in these cells? Choose one: a. IRE1 b. IRE1 and ATF6 c. ATF6 d. IRE1 and PERK e. PERK

IRE1 and PERK

What would happen to a protein that is engineered to contain both a nuclear localization signal and a nuclear export signal? Choose one: a. It would shuttle in and out of the nucleus. b. It would bind to nuclear import receptors and nuclear export receptors, forming a nonfunctional complex. c. It would spend most of its time in the cytosol. d. It would spend most of its time in the nucleus. e. It would be unable to fold properly and would be targeted for destruction.

It would shuttle in and out of the nucleus.

Which of these statements is true? Choose one: a. The N-terminus of a protein translocated into the ER will always remain in the ER lumen. b. Membrane-bound ribosomes and free ribosomes are structurally and functionally identical; they differ only in the proteins they are making at a particular time. c. Attachment to a polyribosome prevents a growing polypeptide chain from being translocated into the ER. d. Only those proteins that are destined to remain inserted in the membrane are made on the rough ER; soluble proteins are made in the cytosol. e. The signal sequence that directs a growing polypeptide chain to enter the ER membrane is always removed by a transmembrane signal peptidase.

Membrane-bound ribosomes and free ribosomes are structurally and functionally identical; they differ only in the proteins they are making at a particular time.

How does the nuclear pore restrict the passage of large molecules that do not bear the correct nuclear localization signal? Choose one: a. Nuclear pore proteins contain disordered segments that form a gel-like meshwork inside the pore. b. The hydrophobic interior of the pore repels proteins that lack the correct nuclear localization signal. c. Inbound proteins are captured by the nuclear basket and released by GTP hydrolysis. d. The cytosolic fibrils obstruct access to the pore and can only be parted by nuclear import receptors. e. The pores remain closed until they are stimulated by the binding of proteins with the proper localization signal.

Nuclear pore proteins contain disordered segments that form a gel-like meshwork inside the pore.

Nuclear import is driven by the hydrolysis of GTP, which is triggered by an accessory protein called Ran-GAP (GTPase-activating protein). Which is true of this process? Choose one: a. Ran-GTP is present in high concentrations in the cytosol. b. Nuclear receptors carry Ran-GTP from the nucleus to the cytosol. c. Ran-GDP displaces proteins from nuclear import receptors inside the nucleus. d. Ran-GAP is present exclusively in the nucleus. e. Nuclear import receptors have the ability to catalyze hydrolysis of GTP.

Nuclear receptors carry Ran-GTP from the nucleus to the cytosol.

A certain membrane protein is found on the ER membrane with the N-terminus on the ER side of the membrane and the C-terminus on the cytosol side of the membrane. The protein contains three transmembrane domains. What would be the orientation of the protein across the ER membrane if the gene were mutated such that the third transmembrane domain coded for hydrophilic amino acids? Choose one: a. Orientation A b. Orientation B c. Orientation C d. Orientation D

Orientation B

Match each of the following functions with the protein that completes that function. Items (4 items) Proteasome Ribosome Chaperone eIF2

Proteasome: degrades misfolded proteins Ribosome: synthesizes proteins Chaperone: helps proteins properly fold eIF2: controls rate of translation initiation

(Q017) What is one of the main differences in the behavior of the proteins in a vesicle destined for constitutive secretion, and the proteins in the vesicles destined for regulated secretion? a. Proteins in the constitutive secretion vesicle unfold to keep the concentration in the vesicle low, and then refold at the cell surface b. The regulated secretion vesicle proteins are bound to lipids for supplying the plasma with new lipids c. Proteins in the constitutive secretion vesicles are stored for release in response to a signal d. Proteins in the regulated secretion vesicle tend to aggregate and become highly concentrated in the ionic conditions in the vesicle

Proteins in the regulated secretion vesicle tend to aggregate and become highly concentrated in the ionic conditions in the vesicle

What is one of the main differences in the behavior of the proteins in a vesicle destined for constitutive secretion, and the proteins in the vesicle destined for regulated secretion? Choose one: A. Proteins in the constitutive secretion vesicle unfold to keep the concentration in the vesicle low, and then refold at the cell surface. B. Proteins in the regulated secretion vesicle tend to aggregate and become highly concentrated in the ionic conditions in the vesicle. C. The regulated secretion vesicle proteins are bound to lipids for supplying the plasma with new lipids. D. Proteins in the constitutive secretion vesicle are stored for release in response to a signal.

Proteins in the regulated secretion vesicle tend to aggregate and become highly concentrated in the ionic conditions in the vesicle.

Investigators have engineered a gene that encodes a protein bearing an ER signal sequence followed by a nuclear localization signal. What would be the likely fate of that protein?Choose one: a. Because of its conflicting signals, the protein will be sent to a lysosome for destruction. b. Because of its conflicting signals, the protein will remain in the cytosol. c. Because of its conflicting signals, the protein will be degraded in the cytosol. d. The protein will be recognized by a nuclear import receptor and escorted into the nucleus. e. The protein will be recognized by an SRP and enter the ER.

The protein will be recognized by an SRP and enter the ER.

Put the following steps used to transport proteins into mitochondria into the proper order.

The mitochondrial protein is synthesized in the cytosol, The receptor on the mitochondrial membrane binds the signal sequence on the protein, The protein is delivered to the translocation apparatus on the mitochondria, The protein is passed through the translocation apparatus.

Ricin is one of the most powerful toxins known. The protein consists of two subunits: the A chain is an enzyme that inhibits translation and the B chain is a lectin that binds to carbohydrates on the cell surface. What is the most likely mechanism by which ricin enters the cell?Choose one: a. The protein is internalized by endocytosis. b. The A chain binds to clathrin. c. The A chain stimulates autophagy. d. The protein enters through pore complexes in the plasma membrane. e. The B chain interacts with SNAREs.

The protein is internalized by endocytosis.

To determine whether a signal sequence directs proteins to a particular organelle, researchers prepare two versions of the same protein: one version contains the signal sequence, while the other lacks it. They label the protein that contains the signal sequence with a radioactive marker, and then incubate both of the proteins with the organelle of interest.After allowing enough time for any of the proteins to be transported into the organelle, a protease is added to the mixture.If the signal sequence is the correct one for the selected organelle, what would the researchers likely see? Choose one: a. The radioactive label would be associated with an intact protein. b. The radioactive label would be associated with one particular protein fragment. c. The radioactive label would be associated with a collection of protein fragments. d. The radioactive label would be associated with the protease. e. The radioactive label would be destroyed.

The radioactive label would be associated with an intact protein.

Proteins entering the cis Golgi network can do which of the following?Choose one: a. They can either move onward through the Golgi stack or be returned to the ER. b. They can either move backward to the trans Golgi network or be sent forward to the plasma membrane. c. They are sorted according to whether they are destined for lysosomes or for the cell surface. d. They are either sent to the nucleus or to the plasma membrane for secretion. e. They can be held in the cis Golgi while they are properly folded and assembled.

They can either move onward through the Golgi stack or be returned to the ER.

(Q011) A single-pass transmembrane protein destined for one of the organelles in the endomembrane system would be marked by what type of signal sequence? a. an internal ER signal sequence and an internal stop-transfer sequence b. a cleaved N-terminal ER signal sequence c. an internal ER signal sequence d. a cleaved N-terminal ER signal sequence and an internal stop-transfer sequence

a cleaved N-terminal ER signal sequence and an internal stop-transfer sequence

A single-pass transmembrane protein destined for one of the organelles in the endomembrane system would be marked by what type of signal sequence?Choose one: A. a cleaved N-terminal ER signal sequence B. a cleaved N-terminal ER signal sequence and an internal stop-transfer sequence C. an internal ER signal sequence and an internal stop-transfer sequence D. an internal ER signal sequence

a cleaved N-terminal ER signal sequence and an internal stop-transfer sequence

Botulism is a potentially fatal foodborne disease caused by the bacterium Clostridium botulinum. C. botulinum produces different toxins, several of which are proteases that cleave neuronal SNARE proteins. What normal process is blocked by cleavage and inhibition of SNARE proteins? Choose one: A. docking of vesicles to target membranes B. budding of vesicles from the endoplasmic reticulum C. entry of proteins with ER signal sequences into the ER lumen D. fusion of vesicles with target membranes

fusion of vesicles with target membranes

Trypanosomes are single-celled parasites that cause sleeping sickness when they infect humans. Trypanosomes taken from infected humans are known to store the enzymes needed to carry out some of the reactions of glycolysis in an organelle that resembles the peroxisome. In contrast, trypanosomes taken from tsetse flies—the intermediate host—carry out glycolysis entirely in the cytosol.Investigators at a pharmaceutical company decide to follow up on this observation to design a potential new therapeutic. They determine that in trypanosomes from tsetse flies, one of the glycolytic enzymes, phosphoglycerate kinase (PGK), is present entirely in the cytosol, whereas in parasites taken from humans, 90% of the PGK activity is in a peroxisome-like compartment and only 10% is in the cytosol.When the investigators clone the PGK genes, they discover that the parasites have three forms, each of which differs slightly from the others. They design probes that hybridize specifically to the mRNAs from each gene and then use these probes to determine which genes are expressed by trypanosomes from humans (H) and which are expressed by trypanosomes from tsetse flies (F).Shown here is a gel in which mRNAs purified from the two different trypanosomes have been separated by size and exposed to probes that recognize the three different forms of the PGK gene (genes 1, 2, and 3). Based on these results, which gene most likely encodes the peroxisomal form of PGK? Choose one: a. gene 1 b. both genes 1 and 3 c. gene 3 d. gene 2 e. both genes 1 and 2

gene 3

Insulin is synthesized in the form of a precursor protein that requires cleavage of two different peptide segments before the mature protein is secreted from β cells in the pancreas. The first peptide is removed when the protein enters the lumen of the ER. To find out when the second cleavage event takes place, investigators prepare a pair of antibodies: one recognizes the pro-insulin precursor, the other the mature insulin protein. They tag the antibody that binds to the precursor protein with a red fluorescent marker; the antibody that binds to mature insulin is tagged with a green fluorescent marker. When both markers are present, the sample fluoresces yellow.The investigators then incubate an isolated β cell with both antibodies at the same time and monitor the fluorescence in its various membrane-bound compartments. The data are shown in the table below. Based on these observations, where is the second peptide removed from the pro-insulin precursor protein? Choose one: a. ER b. immature secretory vesicles c. Golgi apparatus d. mature secretory vesicles e. lysosomes

immature secretory vesicles

(Q010) Proteins encoded by nuclear genes and destined for the mitochondrial matrix are: a. transported across the membrane as a folded protein b. synthesized on ribosomes on the rough ER c. in possession of a signal sequence for targeting to the mitochondria d. able to diffuse into the mitochondrial intermembrane space first

in possession of a signal sequence for targeting to the mitochondria

Which membrane-enclosed organelles most likely evolved in a similar manner? Choose one: A. the nucleus and the ER B. mitochondria and the nucleus C. chloroplasts and peroxisomes D. mitochondria and the ER E. mitochondria and the Golgi apparatus

the nucleus and the ER

In a classic experiment designed to study nuclear transport, investigators added a dye molecule to the subunits of a protein called nucleoplasmin, which is involved in chromatin assembly. They then injected the intact protein or combinations of its subunits into the cytosol of a frog oocyte or into its nucleus. The results of the experiment are shown in the diagram, where red indicates the location of the labeled protein. Based on these results, which part of the nucleoplasmin protein bears a nuclear localization signal? Choose one: a. the head only b. the tail only c. No conclusion about the nuclear localization signal can be drawn from the data. d. neither the head nor the tail e. both the head and the tail

the tail only

(Q014) In which process do Rab proteins function? a. vesicle tethering b. vesicle fusion c. cargo protein delivery d. vesicle docking

vesicle tethering

Which molecule is displaced when a vesicle and its target membrane fuse? Choose one: a. clathrin b. phospholipids c. tethering proteins d. SNAREs e. water

water