Chapter 15 Quiz

5.Which organelle sorts ingested molecules and recycles some of them back to the plasma membrane? A. An endosome B. The Golgi apparatus C. A lysosome D. The endoplasmic reticulum E. A peroxisome

A. An endosome

8.The interiors of the ER, Golgi apparatus, endosomes, and lysosomes communicate with each other in which of the following ways? A. By small vesicles that bud off of one organelle and fuse with another B. By open pores that allow ions to exit and enter the organelles C. They do not communicate with one another. D. By excreting hormones and other small signaling molecules

A. By small vesicles that bud off of one organelle and fuse with another

29.How do proteins travel from one cisterna to the next in the Golgi apparatus? A. By transport vesicles that bud off from one cisterna and fuse with the next cisterna B. By physical connections between two cisternae C. Through pores in the membranes of cisternae

A. By transport vesicles that bud off from one cisterna and fuse with the next cisterna

9.Most mitochondrial and chloroplast proteins are made in which compartment of the cell? A. In the cytosol B. In the endoplasmic reticulum C. Within the mitochondrion or chloroplast

A. In the cytosol

19.In the process of translocating a polypeptide across the membrane of the endoplasmic reticulum, a stop transfer sequence halts the process. What eventually becomes of the stop transfer sequence? A. It forms an /alpha-helical membrane-spanning segment of the protein. B. It is cleaved from the protein. C. It is translocated into the lumen of the endoplasmic reticulum.

A. It forms an /alpha-helical membrane-spanning segment of the protein.

12.Proteins have to unfold during their transport across the membranes of all but one of the following organelles. Which one? A. The nucleus B. Mitochondria C. Chloroplasts D. The endoplasmic reticulum

A. The nucleus

30.Proteins entering the cisGolgi network can do which of the following? A. They can either move onward through the Golgi stack or be returned to the ER. B. They can either move backward through the Golgi stack or be sent to the plasma membrane. C. They are sorted according to whether they are destined for lysosomes or for the cell surface.

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

32.What distinguishes proteins destined for regulated secretion? A. They have special surface properties that cause them to form aggregates that are packaged into secretory vesicles. B. They have a series of amino acids that act as a tag that marks them for packaging into secretory vesicles. C. They are cleaved from membrane domains in the Golgi apparatus prior to being packed into secretory vesicles.

A. They have special surface properties that cause them to form aggregates that are packaged into secretory vesicles.

22.Vesicle budding is driven by the assembly of a protein coat. A. True B. False

A. True

31.The constitutive exocytosis pathway of the Golgi apparatus operates continually in all eucaryotic cells. A. True B. False

A. True

11.If a signal sequence is removed from an ER protein: A. the protein remains in the cytosol. B. the protein will enter an organelle other than the ER. C. the protein will be immediately degraded. D. the protein will be exported from the cell.

A. the protein remains in the cytosol.

17.Which of the following is true? A. A special class of ribosomes embedded in the ER translates the proteins destined for that organelle. B. A common pool of ribosomes is used to synthesize both the proteins that stay in the cytosol and those that are destined for the ER. C. All ribosomes are attached to the ER when they are synthesizing a protein.

B. A common pool of ribosomes is used to synthesize both the proteins that stay in the cytosol and those that are destined for the ER.

21.What protein can assemble into a basket-like network that gives budding vesicles their shape? A. Dynamin B. Clathrin C. Actin D. Myosin

B. Clathrin

20.The movement of materials from the plasma membrane, through endosomes, and then to lysosomes describes which type of pathway? A. Secretory pathway B. Endocytic pathway C. Exocytic pathway

B. Endocytic pathway

13.Which proteins bind to nuclear localization signals on newly synthesized proteins? A. Nuclear pore proteins B. Nuclear import receptors C. Signal-recognition particles D. Nuclear fibrils

B. Nuclear import receptors

10.Proteins that lack a sorting signal remain as permanent residents of which part of a eucaryotic cell? A. The nucleus B. The cytosol C. The endoplasmic reticulum D. The Golgi apparatus E. A lysosome

B. The cytosol

1.The outer membrane of the nucleus is continuous with the membrane of which other organelle? A. A mitochondrion B. The endoplasmic reticulum C. The Golgi apparatus D. A peroxisome

B. The endoplasmic reticulum

2.Which organelle is the major site of new membrane synthesis in a cell? A. A mitochondrion B. The endoplasmic reticulum C. The Golgi apparatus D. The nucleus

B. The endoplasmic reticulum

24.Which molecule is displaced when a vesicle and its target membrane fuse? A. SNARES B. Water C. Phospholipids D. Cholesterol E. Tethering proteins

B. Water

33.Cells ingest large particles by: A. pinocytosis. B. phagocytosis. C. megacytosis.

B. phagocytosis.

4.Which organelle is essentially a small sac of digestive enzymes that functions in degrading worn-out organelles, as well as macromolecules and particles taken into the cell by endocytosis? A. An endosome B. The Golgi apparatus C. A lysosome D. The endoplasmic reticulum E. A peroxisome

C. A lysosome

27.Which type of protein binds to improperly folded or improperly assembled proteins in the ER, holding them there until proper folding occurs? A. Tethering proteins B. Glycosylating proteins C. Chaperone proteins D. Antibody proteins

C. Chaperone proteins

38.Which cellular compartment acts as the main sorting station for extracellular cargo molecules taken up by endocytosis? A. Transport vesicles B. The Golgi apparatus C. Endosomes D. Lysosomes

C. Endosomes

7.Which of the following organelles is not surrounded by a double membrane? A. Mitochondrion B. Chloroplast C. Golgi apparatus D. Nucleus

C. Golgi apparatus

39.Which of the following is true of lysosomes? A. The products of digestion in lysosomes leave the lysosome by transport vesicles. B. Most of the lysosomal membrane proteins have glycosylated regions on the cytosolic side of the membrane. C. Lysosomal enzymes are optimally active in the acidic conditions maintained within lysosomes. D. Lysosomes form from vesicles that pinch off from the endoplasmic reticulum.

C. Lysosomal enzymes are optimally active in the acidic conditions maintained within lysosomes.

3.Which organelle receives proteins and lipids from the endoplasmic reticulum, modifies them, and then dispatches them to other destinations in the cell? A. A mitochondrion B. An endosome C. The Golgi apparatus D. The nucleus E. A peroxisome

C. The Golgi apparatus

14.Which of the following statements is NOT true of mitochondrial proteins that are synthesized in the cytosol? A. The proteins are unfolded as they are transported into the mitochondria. B. The proteins cross both the inner and outer mitochondrial membranes as they are imported. C. The proteins are transported across the mitochondrial membranes while being synthesized. D. Chaperone proteins help draw the proteins inside the mitochondrion. E. The proteins usually have a signal sequence at their N-terminus.

C. The proteins are transported across the mitochondrial membranes while being synthesized.

26.Which of the following is NOT a role for the oligosaccharides on glycosylated proteins? A. They can protect the protein from degradation and hold it in the ER until it is properly folded. B. They can guide the protein to the appropriate organelle by serving as a transport signal for packaging the protein into appropriate transport vesicles. C. They can provide a source of energy for the cell. D. When displayed on the cell surface, oligosaccharides form part of the cell's carbohydrate layer and can function in the recognition of one cell by another.

C. They can provide a source of energy for the cell.

37.The low pH inside endosomes: A. destroys internalized cargo proteins. B. destroy internalized receptors. C. causes internalized receptors to release their cargo. D. causes cargo proteins to bind to their receptors.

C. causes internalized receptors to release their cargo.

35.Eukaryotic cells continually ingest bits of their plasma membrane, along with small amounts of extracellular fluid. The lost pieces of membrane are replaced by the process of: A. pinocytosis. B. phagocytosis. C. exocytosis. D. endocytosis.

C. exocytosis.

18.The ER signal sequence on a growing polypeptide chain is recognized by a signal recognition particle (SRP) in the cytosol. This interaction: A. causes the polypeptide chain to dissociate from the ribosome. B. causes the ribosome to return to the pool of free ribosomes in the cytosol. C. guides the ribosome and its polypeptide to the ER membrane. D. speeds the synthesis of the polypeptide chain.

C. guides the ribosome and its polypeptide to the ER membrane.

16.Proteins in the cytosol that are destined for other organelles must first enter the: A. the nucleus. B. the Golgi apparatus. C. the endoplasmic reticulum. D. the lysosomes.

C. the endoplasmic reticulum.

25.Many proteins are glycosylated in: A. the cytosol. B. mitochondria. C. the endoplasmic reticulum. D. lysosomes. E. peroxisomes.

C. the endoplasmic reticulum.

40.Which mechanism is used for degrading obsolete parts of a cell, such as a defective mitochondrion? A. Phagocytosis B. The unfolded protein response C. Apoptosis D. Autophagy

D. Autophagy

36.Which of the following is NOT true of receptor-mediated endocytosis? A. In receptor-mediated endocytosis, extracellular substances are internalized in clathrin-coated vesicles. B. Low-density lipoproteins (LDLs) are taken into cells by receptor-mediated endocytosis. C. Some viruses are taken into the cell by receptor-mediated endocytosis. D. In receptor-mediated endocytosis, internalized vesicles fuse with lysosomes, which then mature into endosomes.

D. In receptor-mediated endocytosis, internalized vesicles fuse with lysosomes, which then mature into endosomes.

28.In the unfolded protein response, the accumulation of misfolded proteins in the ER serves as a signal for the cell to do which of the following? A. Glycosylate the misfolded protein B. Increase the transport of misfolded proteins to the Golgi apparatus C. Export the misfolded proteins to the cytosol D. Produce more ER

D. Produce more ER

15.Mitochondria and peroxisomes do NOT have what in common? A. Their membranes contain a protein translocator. B. They are present in eukaryotic cells. C. They must import proteins to function. D. Proteins need to unfold to enter them.

D. Proteins need to unfold to enter them.

34.Phagocytic cells include: A. neutrophils and red blood cells. B. red blood cells and liver cells. C. protozoa and bacteria. D. macrophages and neutrophils

D. macrophages and neutrophils.

6.Which organelle contains enzymes used in a variety of oxidative reactions that break down lipids and destroy toxic molecules? A. A mitochondrion B. An endosome C. A lysosome D. The endoplasmic reticulum E. A peroxisome

E. A peroxisome

23.Which proteins play a central role in the fusion of a vesicle with a target membrane? A. Rab proteins B. Tethering proteins C. Adaptin proteins D. Clathrin proteins E. SNARE proteins

E. SNARE proteins