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Chapter 2: The Cytoplasm

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In transmission EM preparations of cells the cell membrane often appears as a trilaminar structure having two parallel dark-staining components on either side of an unstained middle layer. This central poorly stained region of the membrane is primarily responsible for which of the following functions?

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a. Creation of a barrier to water-soluble molecules

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b. Binding by cellular receptions to specific ligands

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c. Catalyzing membrane-associated activities

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d. Transport of ions

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e. Connections to the cytoskeleton

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Chaperonins are cytoplasmic proteins most likely to be found in which of the following organelles?

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a. Lysosomes

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b. Golgi complexes

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c. Rough endoplasmic reticulum

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d. Smooth endoplasmic reticulum

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e. Mitochondria

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Which of the following best defines the term “exocytosis"?

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a. The discharge of ions or small molecules from a cell by protein pumps in the cell membrane

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b. The uptake of material at one domain of a cell’s surface and its discharge from the opposite side of the cell

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c. The process by which proteins move from one cytoplasmic compartment to another

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d. The discharge of proteins in cytoplasmic vesicles from a cell following fusion of the vesicles with the plasmalemma

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e. Diffusion of lipid-soluble molecules from a cell across the cell membrane

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Cytoplasm often stains poorly because its lipid content is removed by the organic solvents used in the clearing step in routine histological preparations. This problem is most likely to occur with cytoplasmic regions rich in which of the following organelles?

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a. Free polysomes

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b. Mitochondria

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c. Lysosomes

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d. Smooth endoplasmic reticulum

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e. Rough endoplasmic reticulum

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Polarity in microtubules is important in determining which of the following?

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a. The strength of vinblastine binding to microtubules

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b. The velocity of transport along microtubules with myosin motors

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c. The overall dynamic instability of the microtubules

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