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Which of the following best describes the general structure of a cell membrane? |
proteins embedded in two layers of phospholipid |
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Stability of an animal cell plasma membrane is enhanced by _____. |
cholesterol molecules |
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As shown below, proteins perform a number of functions within membranes. Which of the following statements is true about membrane proteins? |
Proteins can bind other molecules, which may trigger specific cellular functions. |
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Phospholipids are well suited to be the main structural components of membranes because they _____. |
so that the nonpolar parts of two lipids point toward each other |
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The membrane is referred to as a "fluid mosaic" structure. Which of the following statements is true? |
The fluid is phospholipid, and the mosaic is protein. |
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The lipids in a cell membrane are arranged _____. |
so that the nonpolar parts of two lipids point toward each other |
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When considering the formation of membranes, they _____. |
form spontaneously in aqueous environments |
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In the figure below, working from the inside out, what would be the order of components observed? |
water, hydrophilic head, hydrophobic tail, hydrophobic tail, hydrophilic head, water |
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Which of the following statements is true about passive transport? |
Passive transport requires no expenditure of cellular energy. |
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The movement of atoms, ions, or molecules from a region of higher concentration to regions of lower concentration is called _____. (see book section: Module 5.4) |
diffusion |
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The diffusion of water across a selectively permeable membrane is called _____. |
osmosis |
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Which of the following statements is true about diffusion? |
It is a passive process. |
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Cells A and B are the same size and shape, but cell A is metabolically quiet and cell B is actively consuming oxygen. Oxygen will diffuse more quickly into cell _____ because _____. |
B … the diffusion gradient there is steeper |
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The concentration of solutes in a red blood cell is about 2%. Sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink the most when immersed in which of the following solutions? |
a hypertonic sucrose solution |
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Green olives may be preserved in brine, which is a 20-30% salt solution. How does this method prevent contamination by microorganisms? |
Bacteria can’t survive in a hypertonic solution because they lose water. |
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Seawater is dangerous to drink because _____. |
seawater is hypertonic to your body tissues and drinking it will cause you to lose water by osmosis |
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Which of these situations accurately represents osmoregulation in organisms? |
Plant cells need a hypotonic environment in order to stay turgid. |
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If the volume of a cell increases when it is placed in an aqueous solution, that solution is said to be _____ to the cell. |
hypotonic |
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Which of these statements describes what occurs in facilitated diffusion? (see book section: Module 5.5) |
Facilitated diffusion of solutes occurs through protein pores in the membrane. |
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Review the figure below of passive transport, then choose one of the following statements as being descriptive of this process. |
Passive transport transports molecules without the assistance of proteins from an area of high concentration to an area of lower concentration. |
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Which of the following is a difference between active transport and facilitated diffusion? |
Active transport requires the expenditure of cellular energy, and facilitated diffusion does not. |
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What condition might result from an excess of aquaporins? |
fluid retention in pregnant women |
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When in solution, a molecule that moves slowly across an artificial membrane moves rapidly across a plasma membrane. This occurs regardless of whether the concentration of this molecule is higher inside or outside the cell. Using this information, which transport mechanism is most likely to be responsible for the movement of the molecule across a plasma membrane? |
active transport |
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The transport of molecules of a particular solute from inside an animal cell across the cell membrane to the extracellular fluid always requires energy when _____. |
the concentration of the solute is lower inside the cell than outside it |
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Which of the following statements about cell membrane transport is true? |
Active transport works with the assistance of proteins to move molecules from areas of low concentration to areas of high concentration. |
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Which of the following enables a cell to pick up and concentrate a specific kind of molecule? |
receptor-mediated endocytosis |
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A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother’s milk. These molecules probably enter the cells lining the baby’s digestive tract via _____. |
endocytosis |
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Which of the following terms specifically refers to the intake of very large particles by cells? |
phagocytosis |
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Some liver cells ingest bacteria, a function probably accomplished by _____. |
phagocytosis |
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Which statement best describes phagocytosis? |
A cell engulfs a particle by wrapping pseudopodia around it and packaging it within a vacuole. |
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The secretion of neurotransmitters out of the nerve cell, from small vesicles at the end of the axon, can be considered an example of _____. |
exocytosis |
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LDLs enter cells by means of _____. |
receptor-mediated endocytosis |
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Energy is _____. |
the capacity to perform work |
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According to the second law of thermodynamics, which of the following is true? |
The ordering of one system depends on the disordering of another. |
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Which of the following is an example of the second law of thermodynamics? |
The aerobic respiration of glucose generates heat. |
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If the entropy of a system is increasing, this means that _____. |
energy input will be needed to maintain organization |
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The first law of thermodynamics _____. |
states that energy is neither created nor destroyed |
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Cellular respiration is an example of _____. |
an exergonic reaction |
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A reaction is designated as exergonic rather than endergonic when _____. |
the potential energy of the products is less than the potential energy of the reactants |
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Most cellular work is accomplished by _____ energizing molecules by _____ them. |
ATP … phosphorylating |
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The phosphorylation of ADP to form ATP is an _____ reaction that _____ energy. |
endergonic … requires an input of |
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The mechanism of enzyme action is to _____. |
lower the energy of the activation of a reaction |
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If the tertiary structure of an enzyme is changed, _____. |
its substrate may not fit properly in the active site |
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Taq polymerase is an enzyme isolated from the organism Thermophilus aquaticus. This organism has been found living in the hot springs of Yellowstone National Park. This enzyme is used to copy human DNA from crime scenes. Most reactions are performed at ranges similar to those of the human body; however, what considerations should be made for optimum use of this enzyme? |
The temperature should be raised. |
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Succinylcholine is structurally almost identical to acetylcholine, but if combined with the enzyme that normally hydrolyzes acetylcholine, the enzyme is no longer able to hydrolyze acetylcholine. This suggests that _____. |
succinylcholine must be a competitive inhibitor of acetylcholine |
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Which of these statements about enzyme inhibitors is true? |
The action of competitive inhibitors may be reversible or irreversible. |
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Why doesn’t the antibiotic penicillin harm humans? |
Human cells do not have cell walls. |
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