Molecular Cell Biology Problem Drill 16: Intracellular Compartment and Protein Sorting Question No. 1 of 10 Question 1. Which of the following statements about the nucleus is correct? Question #01 A. The nucleus is surrounded by a nuclear envelope, which is made up of a single lipid membrane. B. The nuclear envelope contains small openings called nuclear pores; these pores are aqueous channels that allow small molecules to pass in and out of the nucleus, while keeping the genetic material inside. C. The nuclear envelope contains large openings called nuclear pores; these pores allow the genetic material to exit the nucleus. D. The nucleolus is a small region inside the nucleus that is surrounded by 2 lipid membranes. The nucleus is surrounded by a nuclear envelope, which is made up of 2 lipid membranes. B. Correct! The nuclear envelope contains small openings called nuclear pores; these pores are aqueous channels that allow small molecules to pass in and out of the nucleus, while keeping the genetic material inside. The nuclear envelope contains small openings called nuclear pores; these pores are aqueous channels that allow small molecules to pass in and out of the nucleus, while keeping the genetic material inside. The nucleolus is a small region inside the nucleus that is not surrounded by a membrane.. The nucleus is usually located in the center of the cell and is the storage facility for the human genome. The nucleus is surrounded by a nuclear envelope, which is made up of 2 lipid membranes. The nuclear envelope contains small openings called nuclear pores; these pores are aqueous channels that allow small molecules to pass in and out of the nucleus, while keeping the genetic material inside. The nucleolus is a small region inside the nucleus that is not surrounded by a membrane. This is where ribosomal RNA is synthesized and assembled with other ribosome components.
Question No. 2 of 10 Question 2. Endoplasmic reticulum. Question #02 A. The endoplasmic reticulum (ER) is a network of sac-like structures, known as cisternae, that is physically separate from the nucleus. B. Rough ER, which has a lot of integral ribosomes that are irreversibly bound to its surface. C. Rough ER, which has a lot of ribosomes that are reversibly bound to its surface. These ribosomes bind to the rough ER during the synthesis of proteins, which need to be sorted within the cell. D. The rough ER works with the lysosomes to target proteins to their final destination. The endoplasmic reticulum (ER) is a network of sac-like structures, known as cisternae, and is continuous with the nucleus. Facilitates the movement of a molecule down its concentration gradient, this is a passive process. C. Correct! Is the process by which a carrier protein or channel protein facilitates the transport of a molecule down its concentration gradient. The rough ER works with the golgi apparatus to target proteins to their final destination. The endoplasmic reticulum (ER) is a network of sac-like structures, known as cisternae, and is continuous with the nucleus. There are 2 varieties of ER:(A) Smooth ER: which is made up of tubes that form a branching network. The smooth ER is involved in the synthesis of lipids, metabolism of carbohydrates and storage of large amounts of calcium in muscle cells. (B) Rough ER: which has a lot of ribosomes that are reversibly bound to its surface. These ribosomes bind to the rough ER during the synthesis of proteins, which need to be sorted within the cell. The rough ER works with the golgi apparatus to target proteins to their final destination.
Question No. 3 of 10 Question 3. Which of the following statements about mitochondria is correct? Question #03 A. The mitochondria do not contain genetic material and therefore must import all of the needed proteins it. B. The mitochondria contain its own genetic material and can synthesize some of the needed proteins it. C. The primary function of the mitochondria is GTP production, via the oxidation of pyruvate, utilizing electron transport and oxidative phosphorylation. D. The primary function of the mitochondria is ATP production, via the oxidation of lactose, utilizing electron transport and oxidative phosphorylation. The mitochondria contain its own genetic material and can synthesize some of the needed proteins it. B. Correct! The mitochondria contain its own genetic material and can synthesize some of the needed proteins it. The primary function of the mitochondria is ATP production, via the oxidation of pyruvate, utilizing electron transport and oxidative phosphorylation. The primary function of the mitochondria is ATP production, via the oxidation of pyruvate, utilizing electron transport and oxidative phosphorylation. The mitochondria are an organelle made up of an inner matrix surrounded by 2 membranes, in which there is an intermembrane space between. The mitochondria contain its own genetic material and can synthesize some of the needed proteins it. The primary function of the mitochondria is ATP production, via the oxidation of pyruvate, utilizing electron transport and oxidative phosphorylation.
Question No. 4 of 10 Question 4. Which of the following statements about lysosomes is correct? Question #04 A. The lysosome has a single lipid membrane containing H+ proton pumps, which pump in protons from the cytosol to keep the acidic ph of 4.8. B. The lysosome has a single lipid membrane containing H+ proton pumps, which pump out protons from the lysosomes to keep the basic ph of 7.8. C. Lysosomes fuse with phagocytic vesicles and synthesize new proteins. D. Lysosomes fuse with mitochondria and digest/destroy their contents. Lysosomes also are responsible for the degradation of old or damaged organelles. A. Correct! The lysosome has a single lipid membrane containing H+ proton pumps, which pump in protons from the cytosol to keep the acidic ph of 4.8. The lysosome has a single lipid membrane containing H+ proton pumps, which pump in protons from the cytosol to keep the acidic ph of 4.8. Lysosomes fuse with phagocytic vesicles and digest/destroy their contents. Lysosomes also are responsible for the degradation of old or damaged organelles. Lysosomes fuse with phagocytic vesicles and digest/destroy their contents. Lysosomes also are responsible for the degradation of old or damaged organelles. Lysosomes are organelles that contain digestive enzymes that, if not contained, would be harmful to the cell contents. The lysosome has a single lipid membrane containing H+ proton pumps, which pump in protons from the cytosol to keep the acidic ph of 4.8. Lysosomes fuse with phagocytic vesicles and digest/destroy their contents. Lysosomes also are responsible for the degradation of old or damaged organelles.
Question No. 5 of 10 Question 5. Which of the following statements about nuclear protein import is correct? Question #05 A. Proteins that are targeted for the nucleus contain a nuclear localization signal. This signal is an amino acid sequence, usually containing positively charged amino acids, such as histidine and proline. B. The nuclear receptor binds to the protein and lines the pore complex. Once the protein is inside the nucleus, the receptor remains bound to help protein with folding. C. Both import and export of proteins into the nucleus require energy from the hydrolysis of GTP. D. Both import and export of proteins into the nucleus require energy released from the hydrolysis of Acetyl CoA. Proteins that are targeted for the nucleus contain a nuclear localization signal. This signal is an amino acid sequence, usually containing positively charged amino acids, such as lysine and arginine. The nuclear receptor binds to the protein and lines the pore complex. Once the protein is inside the nucleus, the receptor protein dissociates and is able to guide further proteins into the nucleus. C. Correct! Both import and export of proteins into the nucleus require energy released from the hydrolysis of GTP. Both import and export of proteins into the nucleus require energy released from the hydrolysis of GTP. Nuclear import receptors bind the nuclear localization signal portion of the protein and facilitate its transport into the nucleus. The import receptors are soluble proteins that reside inside the nucleus and bind to the localization signal, sometimes with the help of adaptor proteins. The nuclear receptor binds to the protein and lines the pore complex. Once the protein is inside the nucleus, the receptor protein dissociates and is able to guide further proteins into the nucleus. Nuclear export is the reverse of this process and is dependent on nuclear export receptors. Both import and export of proteins into the nucleus require energy released from the hydrolysis of GTP.
Question No. 6 of 10 Question 6. Which of the following statements about mitochondrial protein transport is correct? Question #06 A. Chaperone proteins bind to proteins targeted for the mitochondria and stabilize them in their final folded state. B. Chaperone proteins bind to proteins targeted for the mitochondria and transfer a sugar residue to the NH 2 group of arginine. C. Proteins synthesized in the cytosol on ribosomes undergo posttranslational translocation into the mitochondria. D. Proteins synthesized in the cytosol on ribosomes undergo cotranslational translocation into the mitochondria. Chaperone proteins bind to proteins targeted for the mitochondria and stabilize them in an intermediate unfolded state. Chaperone proteins bind to proteins targeted for the mitochondria and stabilize them in an intermediate unfolded state. C. Correct! Proteins synthesized in the cytosol on ribosomes undergo posttranslational translocation into the mitochondria. Proteins synthesized in the cytosol on ribosomes undergo posttranslational translocation into the mitochondria. Although mitochondria and chloroplasts contain DNA and synthesize the majority of their own proteins, they also must import proteins from the cytosol. Proteins must be imported through both the outer and the inner mitochondrial membrane, based on their unique signal sequence. Proteins synthesized in the cytosol on ribosomes undergo posttranslational translocation into the mitochondria. Proteins are imported through multi-subunit protein complexes, known as translocators. There are specific translocators at the outer and inner mitochondrial membranes. Initially, special proteins in the cytosol, known as chaperones, bind to proteins targeted for the mitochondria and stabilize them in an intermediate unfolded state. Then, the protein binds to the specific outer membrane translocator.
Question No. 7 of 10 Question 7. Which of the following statements about peroxisomes is correct? Question #07 A. Peroxisomes are surrounded by a single lipid bilayer and must import some of their proteins. Peroxisomes are involved in the degradation of molecules, particularly the metabolism of fatty acids. B. Proteins targeted for peroxisomes contain a unique peroxisomal targeting sequence of 3 amino acids. C. Proteins targeted for peroxisomes contain a unique lactose binding region made up of 3 amino acids. D. Proteins have to be unfolded for import into peroxisomes. Peroxisomes are surrounded by a single lipid bilayer and must import all of their proteins. Peroxisomes are involved in the degradation of molecules, particularly the metabolism of fatty acids. B. Correct! Proteins targeted for peroxisomes contain a unique peroxisomal targeting sequence of 3 amino acids. Proteins targeted for peroxisomes contain a unique peroxisomal targeting sequence of 3 amino acids. Proteins imported into peroxisomes do not have to be unfolded, but rather are transported into the organelle in their final folded state. Peroxisomes are surrounded by a single lipid bilayer and must import all of their proteins. Peroxisomes are involved in the degradation of molecules, particularly the metabolism of fatty acids. Once the fatty acids are metabolized to acetyl CoA (ß Oxidation), the acetyl CoA is exported from the peroxisome for use elsewhere in the cell. Proteins targeted for peroxisomes contain a unique peroxisomal targeting sequence of 3 amino acids. The process involves soluble receptor proteins and docking proteins on the cytosolic surface of the peroxisome. Specific proteins called peroxins, of which there are at least 23 members, are involved in the ATP driven process. Proteins imported into peroxisomes do not have to be unfolded, but rather are transported into the organelle in their final folded state.
Question No. 8 of 10 Question 8. Which of the following statements about the role of a signal recognition particle in the import of proteins into the endoplasmic reticulum (ER) is correct? Question #08 A. Signal Recognition Particles (SRP) bind to the signal sequence on the protein as it is being translated. This pauses protein translation, to allow the ribosome-srp complex to binds to a receptor on the ER membrane. B. Signal Recognition Particles (SRP) bind to the signal sequence on the protein after translation is completed, to allow the ribosome-srp complex to binds to a receptor on the ER membrane. C. Signal Recognition Particles (SRP) bind irreversibly to proteins targeted for import into the ER. D. Signal Recognition Particles (SRP) stimulate protein translation when they bind to proteins targeted for import into the ER. A. Correct! Signal Recognition Particles (SRP) bind to the signal sequence on the protein as it is being translated. This pauses protein translation, to allow the ribosome-srp complex to binds to a receptor on the ER membrane. Signal Recognition Particles (SRP) bind to the signal sequence on the protein as it is being translated. This pauses protein translation, to allow the ribosome-srp complex to binds to a receptor on the ER membrane. Signal Recognition Particles (SRP) bind reversibly to proteins targeted for import into the ER. Signal Recognition Particles (SRP) pause protein translation when they bind to proteins targeted for import into the ER. Proteins are transported into the endoplasmic reticulum (ER) during translation, a process called Cotranslational Translocation. The translation of the protein is paused while the complex binds to the ER membrane. Signal Recognition Particles (SRP) bind to the signal sequence on the protein as it is being translated. This pauses protein translation, to allow the ribosome-srp complex to binds to a receptor on the ER membrane.
Question No. 9 of 10 Question 9. Which of the following statements about the endoplasmic reticulum import translocator is correct? Question #09 A. Proteins are imported into the ER through an aqueous pore called the translocator (translocon). B. Proteins are imported into the ER through a non-aqueous pore called the translocator (translocon). C. Accessory proteins, called BiP (binding protein), are chaperone-like proteins that bind irreversibly to the incoming polypeptide chain and facilitate its transport into the ER lumen. D. Accessory proteins, called BiP (binding protein), are chaperone-like proteins that bind to the signal recognition particle and facilitate the transport of the protein into the ER lumen. A. Correct! Proteins are imported into the ER through an aqueous pore called the translocator (translocon). Proteins are imported into the ER through an aqueous pore called the translocator (translocon). Accessory proteins, called BiP (binding protein), are chaperone-like proteins that bind and release, in cycles, to the incoming polypeptide chain and facilitate the transport of the protein into the ER lumen. Accessory proteins, called BiP (binding protein), are chaperone-like proteins that bind and release, in cycles, to the incoming polypeptide chain and facilitate the transport of the protein into the ER lumen. Proteins are imported into the ER through an aqueous pore in protein translocator (translocon). The translocator is made up of a group of 3-4 protein complexes, which assemble to form an aqueous pore. Accessory proteins, called BiP (binding protein), are chaperone-like proteins that bind and release, in cycles, to the incoming polypeptide chain and facilitate the transport of the protein into the ER lumen.
Question No. 10 of 10 Question 10. Which of the following statements about protein glycosylation is correct? Question #10 A. Most proteins synthesized in peroxisomes are modified by the addition of an N-linked oligosaccharide. B. Most proteins synthesized in the rough ER are modified by the addition of an N-linked oligosaccharide. C. This modification is used primarily for targeting old or damaged proteins for degradation in peroxisomes. D. The oligosaccharide is transferred onto a lipid within the protein being modified. Most proteins synthesized in the rough ER are modified by the addition of an N-linked oligosaccharide. B. Correct! Most proteins synthesized in the rough ER are modified by the addition of an N-linked oligosaccharide. This modification is used primarily for secreted proteins, such as glycoproteins, but is also involved in protein folding into its final form. The oligosaccharide is transferred onto the side chain of an asparagine amino acid. Most proteins synthesized in the rough ER are modified by the addition of an N-linked oligosaccharide. The oligosaccharide is transferred onto the side chain of an asparagine amino acid. This modification is used primarily for secreted proteins, such as glycoproteins, but is also involved in protein folding into its final form.