Protein Structure and Function Exam Study Guide: Chapter 3, Exams of Biology

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Chapter 3: Protein

Structure and Function

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1. Which is not a role proteins play in organisms? A) store genetic information B) movement and shape changes C) chemical signaling D) structural support Answer: A Reference: Section 3. Bloom's Level: Remembering LOs: Chp3-1. Explain and give examples of why proteins are essential to cell function.

2. Three important functions of proteins are cell A) wall composition, cushioning, and membrane fluidity. B) movement, signaling, and reaction catalysis. C) information coding, conversion, and transfer. Answer: B Reference: Section 3. Bloom's Level: Remembering LOs: Chp3-1. Explain and give examples of why proteins are essential to cell function.

3. In experiments that successfully simulate chemical evolution, why must at least some small, reduced molecules be present? A) They act as proton donors in acid-base reactions. B) They act as proton acceptors in acid-base reactions. C) They act as electron acceptors in redox reactions. D) They act as electron donors in redox reactions. Answer: D Reference: Section 3. Bloom's Level: Remembering

4. What is the process component of the theory of chemical evolution? A) Acid-base reactions resulted in the formation of large, complex organic molecules. B) Kinetic energy was transformed into chemical energy. C) During polymerization reactions, hydrolysis competed with condensation. D) The process occurred at black smokers, in the atmosphere and oceans, and in outer space. Answer: B Explanation: B) This is a great question to use in class to remind students of the big picture of chemical evolution.

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5. What is the pattern component of the theory of chemical evolution? A) Both heat and electrical discharges are required for chemical evolution to occur. B) Most chemical evolution occurred at black smokers. C) The process occurred at black smokers, in the atmosphere and oceans, and in outer space. D) Increasingly complex carbon-containing molecules formed early in Earth history. Answer: D Reference: Section 3. Bloom's Level: Comprehension

6. Which of the following best describes the first living entity–the one responsible for the origin of life? A) It was a monomer. B) It was large and extremely complex. C) It could make a copy of itself. Answer: C Reference: Section 3. Bloom's Level: Comprehension

7. In interstellar space, millions of ice-encrusted dust particles contain simple carbon-containing compounds. When particles like these are exposed to solar radiation, more complex organic molecules form on the surfaces of the dust. What is the significance of these findings? A) Chemical evolution occurs only in outer space and was not possible on Earth. B) Life began in outer space. C) Life exists in outer space. D) Chemical evolution occurs readily in outer space.

Answer: D Reference: Section 3. Bloom's Level: Comprehension

8. Consider the experiment that Stanley Miller did to simulate chemical evolution. Recall that a glass flask held the reduced gases NH3, CH4, and H2 and that the gases were exposed to

electrical sparks. What is the null hypothesis in the experiment? A) Chemical evolution does not occur. B) Chemical evolution requires the presence of reduced molecules. C) Chemical evolution requires continuous heating. D) Chemical evolution requires a source of kinetic energy. E) Chemical evolution occurs only on Earth.

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Answer: A Reference: Section 3. Bloom's Level: Remembering

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Answer: C Reference: Section 3. Bloom's Level: Remembering LOs: Chp3-2. Sketch the basic structure of an amino acid, and describe why and how the side chains affect the function and structure of each amino acid.

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13. Why are polymerization reactions endergonic? A) They reduce entropy. B) They release heat, making the reactant monomers move faster. C) Because the condensation and hydrolysis reactions are equally spontaneous. D) Because polymers are energetically more stable and have lower potential energy than monomers do. Answer: A Reference: Section 3. Bloom's Level: Remembering

14. At the pH found in cells (about 7.0), what happens to the amino group on an amino acid? A) It acts as a base and gains a proton, giving it a positive charge. B) It acts as an acid and loses a proton, giving it a negative charge. C) It is reduced and tends to act as an electron donor in redox reactions. D) It remains neutral, like water, and does not have a charge. Answer: A Reference: Section 3. Bloom's Level: Comprehension LOs: Chp3-2. Sketch the basic structure of an amino acid, and describe why and how the side chains affect the function and structure of each amino acid.

15. At the pH found in cells (about 7.0), what happens to the carboxyl group on an amino acid? A) It acts as a base and gains a proton, giving it a positive charge. B) It acts as an acid and loses a proton, giving it a negative charge. C) It is oxidized and tends to act as an electron acceptor in redox reactions. D) It remains neutral, like water, and does not have a charge. Answer: B Reference: Section 3. Bloom's Level: Comprehension LOs: Chp3-2. Sketch the basic structure of an amino acid, and describe why and how the side chains affect the function and structure of each amino acid.

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B) It is hydrophilic. C) Relative to the amino acids found in organisms, its interactions with water will be intermediate. D) Relative to the amino acids found in organisms, its interactions with water will be very high. Answer: A Reference: Section 3. Bloom's Level: Applying LOs: Chp3-2. Sketch the basic structure of an amino acid, and describe why and how the side

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chains affect the function and structure of each amino acid.

20. An isomer of a particular molecule is A) a molecule that has the same structure as the target molecule, but a different formula. B) a molecule that is the same except it has an additional side group. C) another copy of the same molecule. D) a molecule that has the same formula, but a different structure. Answer: D Reference: Section 3. Bloom's Level: Remembering LOs: Chp3-2. Sketch the basic structure of an amino acid, and describe why and how the side chains affect the function and structure of each amino acid.

21. A peptide bond is A) an ionic bond, not a covalent one. B) a triple covalent bond. C) a particularly stable, planar covalent bond. D) a particularly unstable covalent bond. Answer: C Reference: Section 3. Bloom's Level: Remembering LOs: Chp3-2. Sketch the basic structure of an amino acid, and describe why and how the side chains affect the function and structure of each amino acid.

22. When polymerization of a protein is complete, but the protein is still completely linear, what is the highest level of structure that has been completed? A) primary B) secondary C) tertiary D) quaternary Answer: A Reference: Section 3. Bloom's Level: Remembering LOs: Chp3-3. Describe the four levels of protein structure, and give examples of each.

23. Which of the following best describes primary structure in proteins? A) It is the number of amino acids present in the complete protein. B) It is the number of peptide bonds in the complete protein.

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24. You are studying a protein that is shaped like a doughnut. The shape is a function of which level(s) of protein structure? A) primary only B) secondary only C) tertiary only D) secondary and tertiary only E) primary, secondary, and tertiary Answer: E Reference: Section 3. Bloom's Level: Remembering LOs: Chp3-3. Describe the four levels of protein structure, and give examples of each.

25. An enzyme has a total of four active sites. When you denature the molecule and study its composition, you find that each active site occurs on a different polypeptide. Which of the following hypotheses does this observation support? A) The enzyme is subject to allosteric regulation. B) The enzyme requires a cofactor to function normally. C) The protein's structure is affected by temperature and pH. D) The protein has quaternary structure. Answer: D Reference: Section 3. Bloom's Level: Comprehension LOs: Chp3-4. Explain what an enzyme is, why enzymes are needed to help chemical reactions proceed in living cells, and the role of the active site.

26. Which of the following observations is the strongest argument in favor of the hypothesis that protein structure and function are correlated? A) Proteins function best at certain temperatures. B) Proteins have four distinct levels of structure and many functions. C) Enzymes tend to be globular in shape. D) Denatured (unfolded) proteins do not function normally. Answer: D Explanation: D) This is a good in-class discussion question to get students to apply their knowledge about protein structure and function. Reference: Section 3. Bloom's Level: Comprehension LOs: Chp3-2. Sketch the basic structure of an amino acid, and describe why and how the side chains affect the function and structure of each amino acid.

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27. You've just sequenced a new protein found in mice and observe that sulfur-containing cysteine residues occur at regular intervals. What is the significance of this finding? A) Cysteine residues are required for the formation of α-helices and β-pleated sheets. B) It will be important to include cysteine in the diet of the mice. C) Cysteine residues are involved in disulfide bridges that help form tertiary structure. D) Cysteine causes bends, or angles, to occur in the tertiary structure of proteins. Answer: C Reference: Section 3. Bloom's Level: Comprehension LOs: Chp3-2. Sketch the basic structure of an amino acid, and describe why and how the side chains affect the function and structure of each amino acid.

28. Recent technological advances have made it more feasible than ever to work out the three- dimensional structure of proteins. There is intense interest in this research field, called structural biology. Why? A) Understanding structure should help us understand function. B) Understanding structure can help in the design of drugs that alter the function of certain proteins. C) Solving a protein's 3-D structure can lead to a better understanding of how the molecule works–for example, by identifying the active site and determining if there are regulatory sites. D) All of the above apply. Answer: D Reference: Section 3. Bloom's Level: Remembering LOs: Chp3-3. Describe the four levels of protein structure, and give examples of each.

29. What type of interaction is directly responsible for the formation of secondary structure? A) peptide bonds between adjacent amino acids B) peptide bonds between nonadjacent amino acids C) hydrogen bonds between sections of the polypeptide backbone D) hydrogen bonds between side chains of amino acids Answer: C Reference: Section 3. Bloom's Level: Remembering LOs: Chp3-3. Describe the four levels of protein structure, and give examples of each.

30. A series of hydrophobic side chains will congregate together as a protein folds in an aqueous solution and be stabilized by

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31. If the primary structure of a protein is incorrect A) the secondary structure will be correct. B) the tertiary structure will be correct. C) any quaternary structure will be correct. D) any higher-level folding of the protein will be incorrect. Answer: D Explanation: D) This question goes to the hierarchical structure of protein folding (purple thematic text) and introduces prion discussion–folding probability, etc. Reference: Section 3. Bloom's Level: Comprehension LOs: Chp3-3. Describe the four levels of protein structure, and give examples of each.

32. You have isolated a previously unstudied protein, identified its complete structure in detail, and determined that it catalyzes the breakdown of a large substrate. You notice it has two binding sites. One of these is large, apparently the bonding site for the large substrate; the other is small, possibly a binding site for a regulatory molecule. What do these findings tell you about the mechanism of this protein? A) It is probably a structural protein that is involved in cell-to-cell adhesion. B) It is probably an enzyme that works through allosteric regulation. C) It is probably an enzyme that works through competitive inhibition. D) It is probably a cell membrane transport protein, like an ion channel. E) It is probably a structural protein found in cartilage or skeletal tissue. Answer: B Reference: Section 3. Bloom's Level: Applying LOs: Chp3-4. Explain what an enzyme is, why enzymes are needed to help chemical reactions proceed in living cells, and the role of the active site.

33. Which of the following is not true when comparing an uncatalyzed reaction to the same reaction with a catalyst? A) The catalyzed reaction will be faster. B) The catalyzed reaction will have a different ∆G. C) The catalyzed reaction will have lower activation energy. D) The catalyzed reaction will not consume any of the catalyst. Answer: B Reference: Section 3. Bloom's Level: Comprehension

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LOs: Chp3-4. Explain what an enzyme is, why enzymes are needed to help chemical reactions proceed in living cells, and the role of the active site.

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37. You've discovered an enzyme that can catalyze two different chemical reactions. Which of the following is most likely to be correct? A) The enzyme contains both α-helices and β-pleated sheets. B) The enzyme is subject to both competitive inhibition and allosteric regulation. C) Two types of allosteric regulation occur—the binding of one molecule activates the enzyme, while the binding of a different molecule inhibits it. D) Either the enzyme has two distinct active sites, or the reactants involved in the two reactions are very similar in size and shape. Answer: D Reference: Section 3. Bloom's Level: Comprehension LOs: Chp3-4. Explain what an enzyme is, why enzymes are needed to help chemical reactions proceed in living cells, and the role of the active site.

38. HIV is the virus that causes AIDS. In the mid-1990s, researchers discovered an enzyme in HIV called protease. Once the enzyme's structure was known, researchers began looking for drugs that would fit into the active site and block it. If this strategy for stopping HIV infections were successful, it would be an example of what phenomenon? A) vaccination B) poisoning C) allosteric regulation D) competitive inhibition Answer: D Reference: Section 3. Bloom's Level: Comprehension LOs: Chp3-4. Explain what an enzyme is, why enzymes are needed to help chemical reactions proceed in living cells, and the role of the active site.

39. Consider the HIV enzyme called protease. The amino acid residues at the active site are highly hydrophobic. In designing a drug that would bind to the active site and jam it, researchers should use which type of molecule? A) hydrophobic B) polar C) charged D) acidic Answer: A Reference: Section 3. Bloom's Level: Remembering

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LOs: Chp3-4. Explain what an enzyme is, why enzymes are needed to help chemical reactions proceed in living cells, and the role of the active site.