Chapter 3 - Cytoplasm and Organelles Flashcards
Which of the following organelles divides by fission? (A) Golgi complex (B) RER (C) Peroxisome (D) SER (E) Centriole
C. A peroxisome originates from preexisting peroxisomes. It imports specific cytosolic proteins and then undergoes fission. The other organelle that divides by fission is the mitochondrion (see receptor-mediated Chapter 3 II A 10).
A 30-year-old man with very high blood cholesterol levels (290 mg/dL) has been diagnosed with premature atherosclerosis. His father died of a heart attack at age 45, and his mother, aged 44, has coronary artery disease. Which of the following is the most likely explanation of his condition?
(A) He has a lysosomal storage disease and cannot digest cholesterol
(B) He has a peroxisomal disorder and produces low levels of hydrogen peroxide
(C) The SER in his hepatocytes has proliferated and produced excessive amounts of cholesterol
(D) He has a genetic disorder and synthesizes defective LDL receptors
(E) He is unable to manufacture endosomes.
D. Cells import cholesterol by the receptor-mediated uptake of LDLs in coated vesicles. Certain individuals inherit defective genes and cannot make LDL receptors, or they make defective receptors that cannot bind to clathrin-coated pits. The result is an inability to internalize LDLs, which leads to high levels of LDLs in the bloodstream. High LDL levels predispose a person to premature atherosclerosis and increase the risk of heart attacks (see Chapter 3 III A 1 Clinical Considerations).
Movement of protein from the RER to the VTC takes place in which of the following cell components? (A) A caveolin-coated vesicle (B) A clathrin-coated vesicle (C) A coatomer I-coated vesicle (D) A coatomer II-coated vesicle (E) An early endosome
D. Transport of protein from the RER to the VTC occurs via (COP-II) coatomer-coated vesicles (see Chapter 3 III B c) .
The retrieval of secretion granule membrane immediately after exocytosis occurs in which of the following cell components? (A) A caveolin-coated vesicle (B) A clathrin-coated vesicle (C) A coatomer I-coated vesicle (D) A coatomer II-coated vesicle (E) An early endosome
B. Membrane recycling after exocytosis of the contents of a secretion granule occurs via clathrin-coated vesicles (see Chapter 3 III A 3).
Movement of protein from trans- to cis-Golgi cisternae occurs in which of the following cell components? (A) A caveolin-coated vesicle (B) A clathrin-coated vesicle (C) A coatomer I-coated vesicle (D) A coatomer II-coated vesicle (E) An early endosome
C. Transfer of material among the cisternae of the Golgi complex in a retrograde direction takes place via (COP-I) coatomer-coated vesicles (see Chapter 3 III B e).
Uncoupling of endocytosed ligands from receptors takes place in which of the following cell components? (A) A caveolin-coated vesicle (B) A clathrin-coated vesicle (C) A coatomer I-coated vesicle (D) A coatomer II-coated vesicle (E) An early endosome
E. The uncoupling of ligands and receptors internalized by receptor-mediated endocytosis occurs in the early endosome (see Chapter 3 II A 9 b).
Movement of acid hydrolases from the TGN to a late endosome takes place in which of the following cell components? (A) A caveolin-coated vesicle (B) A clathrin-coated vesicle (C) A coatomer I-coated vesicle (D) A coatomer II-coated vesicle (E) An early endosome
B. Proteins targeted for lysosomes (via late endosomes) leave the TGN in clathrin-coated vesicles (see Chapter 3 II A 8 a).
Which of the following cytoskeletal components is associated with kinesin? (A) Keratin (B) Lamin A (C) Microfilament (D) Microtubule (E) Neurofilament
D. Kinesin is a force-generating protein associated with microtubules. It serves as a molecular motor for the transport of organelles and vesicles outward, away from the centrosome (see Chapter 3 II C 1).
Which of the following consists of globular actin monomers linked into a double helix? (A) Keratin (B) Lamin A (C) Microfilament (D) Microtubule (E) Neurofilament
C. Globular actin monomers (G actin} polymerize into a double helix of filamentous actin (F actin}, also called a microfilament, in response to the regulatory influence of a number of actin binding proteins (see Chapter 3 II C 2}.
Which of the following has a rigid wall composed of 13 protofilament strands? (A) Keratin (B) Lamin A (C) Microfilament (D) Microtubule (E) Neurofilament
D. A microtubule consistsof alpha- and beta-tubulin dimers polymerized into a spiral around a hollow lumen to form a fairly rigid tubule. When cross-sectioned, the microtubule reveals 13 protofilament strands, which represent the tubulin dimers present in one complete turn of the spiral (see Chapter 3 II C 1).
Which of the following provides structural support to astrocytes? (A) Keratin (B) Lamin A (C) Microfilament (D) Microtubule (E) Neurofilament
E. Glial filaments are a type of intermediate filament composed of GFAP and present in fibrous astrocytes. These filaments are supportive, but they may play additional roles in both normal and pathologic processes in the central nervous system (see Chapter 3 II C 3}.
This tissue section from a tumor has been immunochemically stained for the intermediate filament protein glial fibrillary acidic protein (GFAP). Based on the reddish-brown staining observed (arrow), the tumor has originated from which of the following? A) Oligodendrocytes (B) Chondrocytes (C) Neurons (D) Endothelial cells (E) Fibroblasts
A. The intermediate filament protein GFAP is present in glial cells, including microglia, oligodendrocytes, fibrous astrocytes, and Schwann cells. Vimentin is found in cells of connective tissue origin, which include fibroblasts, chondrocytes, and endothelial cells. Neurons contain intermediate neurofilaments, which would not stain for either GFAP or vimentin (Chapter 3 II C 3 Clinical Considerations).
