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Homework 1 key Ch 1 - 1 The presence of cholesterol in the plasma membranes of some animals A enables the membrane to stay fluid more easily when

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1) The presence of cholesterol in the plasma membranes of some animals A) enables the membrane to stay fluid more easily when cell temperature drops. B) enables the animal to remove hydrogen atoms from saturated phospholipids. C) enables the animal to add hydrogen atoms to unsaturated phospholipids. D) makes the membrane less flexible, allowing it to sustain greater pressure from within the cell. E) makes the animal more susceptible to circulatory disorders. 2) According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids? A) They can move laterally along the plane of the membrane. B) They frequently flip-flop from one side of the membrane to the other. C) They occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane. D) They are free to depart from the membrane and dissolve in the surrounding solution. E) They have hydrophilic tails in the interior of the membrane. 3) The lateral mobility (fluidity) of lipids and proteins in membranes is a consequence of A) lack of covalent bonds between the lipid and protein components of the membrane. B) weak hydrophobic interactions among the components in the interior of the membrane. C) the presence of liquid water in the interior of the membrane. D) A and B only E) A, B, and C 4) What is one of the ways that the membranes of winter wheat are able to remain fluid when it is extremely cold? A) by increasing the percentage of unsaturated phospholipids in the membrane B) by increasing the percentage of cholesterol molecules in the membrane C) by decreasing the number of hydrophobic proteins in the membrane D) A and B only E) A, B, and C 5) The surface of an integral membrane protein would be best described as A) hydrophilic. B) hydrophobic . C) amphipathic. D) completely covered with phospholipids. E) exposed on only one surface of the membrane. 6) What membrane-surface molecules are thought to be most important as cells recognize each other? A) phospholipids B) integral proteins C) peripheral proteins D) cholesterol E) glycoproteins 7) What kinds of molecules pass through a cell membrane most easily? A) large and hydrophobic B) small and hydrophobic C) large polar D) ionic E) monosaccharides such as glucose
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8) Which of the following is a characteristic feature of a carrier protein in a plasma membrane? A) It is a peripheral membrane protein. B) It exhibits a specificity for a particular type of molecule. C) It requires the expenditure of cellular energy to function.
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This note was uploaded on 07/27/2008 for the course BIO SCI 05115 taught by Professor Mcnulty during the Summer '08 term at UC Irvine.

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Homework 1 key Ch 1 - 1 The presence of cholesterol in the plasma membranes of some animals A enables the membrane to stay fluid more easily when

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