Exam 2 Fall 06 Key MCB181R Dr. Jorstad

Exam 2 Fall 06 Key MCB181R Dr. Jorstad - Instructor: Dr. S....

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Instructor: Dr. S. Jorstad Exam II For multiple choice questions (each worth 3 points), bubble all correct answers (there may be more than one); there is a 1 point penalty for incorrect answer choices. For short essays (each worth 5 points): confine your answers to the space provided on the scansheet; writing outside those margins will adversely affect the machine-scoring of your exam; you may use bulleted points to express yourself, as long as your meaning is clear. 1. Cell theory states that a. Life can exist independent of cells. b. All organisms are composed of cells.* c. All cells come from pre-existing cells. * d. Life is continuous: there is a direct connection between cells alive today and cells from 3 billion years ago. * 2. Which of the following statements about the surface-area and volume of cells is/are correct? a. As a cell increases in size, its surface-area-to-volume ratio also increases . (should be decreases) b. The volume of a cell determines the amount of chemical activity a cell can carry out. * c. Large multicellular organisms are unaffected by the surface-area-to-volume ratio problem. d. The surface area of a cell determines the rate at which molecules can be exchanged with the outside environment. * 3. Regarding characteristics of prokaryotes and eukaryotes, a. Prokaryotes live in more diverse environments than eukaryotes. * b. Only eukaryotes have membranes. (prokaryotes have plasma membranes) c. Only eukaryotes have cell walls. (many bacteria have cell walls) d. Only eukaryotes have nuclei. * e. Prokaryotes are the dominant life forms on Earth, if dominance is measured by number of cells or total biomass of cells. * 4. A protein destined for export from a eukaryotic cell a. Is synthesized by proteins in the plasma membrane. b. Is synthesized by ribosomes embedded in the rough endoplasmic reticulum. c. May be modified and tagged (targeted) for its destination by the mitochondria. d. Would arrive at the plasma membrane in a vesicle formed from Golgi membrane. * e. Would most likely be hydrophobic. 5. Cytoskeleton proteins a. Form a fibrous support network throughout the cell to help maintain its shape.* b. Such as kinesin make up flagella and cilia, which function in cell movement. (that would be dynein) 1
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c. Can function to move vesicles or organelles along microtubule tracks. (e.g., kinesin) d. Are found only on the inside of cells, not on the outside. 6. The fluid mosaic model of the plasma membrane a. States that membranes are liquid, mixing freely with the cytoplasm and other substances in the cell. (if this were so, membranes could not form barriers; they would be soluble in aqueous solutions) b. Explains that membranes are made up of many different kinds of molecules.* c. Describes a system of proteins and lipids that are constantly moving (unless they are “corralled” by elements of the cytoskeleton or by lipid “rafts”). * d. Is only a theory; it hasn’t been proven. Short Essay #1: Please confine your answer to the space provided on the scansheet. If
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Exam 2 Fall 06 Key MCB181R Dr. Jorstad - Instructor: Dr. S....

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