Exam1_LyonsBeilstein_Key.pdf

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Department
Ecology & Evolutionary Biology
Course
ECOL 182R
Professor
belstine
Semester
Spring

Description
Exam 1 - Biology 181 Sections 05/06▯▯ ▯ ▯ Lyons/Beilstein Each question is worth 2.5 points. 1. A farmer wishes to develop a strain of high-yield corn that is also resistant to drought. He has the following individuals from the current year's crop: Individual 1—Yield: 220 bushels/acre; drought resistance: high Individual 2—Yield: 220 bushels/acre; drought resistance: low Individual 3—Yield: 185 bushels/acre; drought resistance: medium Individual 4—Yield: 140 bushels/acre; drought resistance: high Individual 5—Yield: 200 bushels/acre; drought resistance: medium Which of the following crosses would most likely produce the highest corn yield with the highest resistance to drought? ▯ A. 1 and 2 B. 2 and 5 C. 2 and 2 D. 1 and 1 E. 2 and 3 (D) Plants can be bred to themselves. One plant maximizes both yield and drought resistance. 2. The role of controls in scientific experiments is to _____, A. Keep conditions as constant as possible. B. Generate large sample sizes that reduce variation. C. Test for factors other than the one being investigated that might influence the outcome of the experiment. D. Allow researchers to conduct experiments with the least possible amount of materials. E. None Of The Above. (C) Experimental “controls” control for variables other then one being tested. 3. Prokaryotic cells are found in the domain(s) _____. A. Bacteria and Archaea B. Bacteria and Eukarya C. Bacteria and Protista D. Bacteria E. Protista and Archaea (A) Prokaryotic means “without nucleus”. Bacteria and Achaea cells lack a nucleus. 4. Looking at the graph above, which statements must be true: 1. Total crop yield has generally increased over time. 2. Protein content has generally decreased over time. 3. Protein content always increases with each generation. 4. There has been selection for larger kernels. A. 1 is true B. 1 and 3 are true C. 2 and 3 are true D. 1, 3 and 4 are true E. None are true (E) The plot is about protein content only. Therefore, 1 and 4 are out. Protein content has increased over time (2 is out), but not with each generation (3 is out). 5. What is evolution? A. The tendency of organisms that are favorably adapted to their environment to survive to reproduce. B. The reproductive isolation of a population that may form a new species. C. The family tree of organisms that describes the genealogical relationships among species with a single ancestral species at its base. D. The accumulation of favorable adaptations in a population of organisms through natural selection over thousands of generations. E. None Of The Above. (D) Definition question. 6. In the above figure, group 1 sat closest to the front of the room and group 4 sat at the back of the room. Assuming that people were randomly assigned to groups, what does the graph show about the difference in behaviors between these groups. A. People who liked to attend class preferentially sat in the front of the room. B. The distance from the front of the room made a difference in the grade people earned in the class. C. There was no difference in attendance based on where people sat. D. People who sat in the front of the class were less likely to attend lectures than those who sat in the back of the class. E. None Of The Above. (E) The data in the graph shows that people who sat in the front of the class were more likely to attend lectures than those who sat in the back, regardless of whether it was the first or second half of the term (though the effect was larger in the second half of the term.) 7. What is the difference between a hypothesis and a scientific theory? A. A hypothesis is a scientific observation that has been repeatedly confirmed; a scientific theory is a theory that has withstood repeated testing and is accepted as being true in all cases. B. A hypothesis is a testable question developed by a scientist based on a series of observations; a scientific theory is a theory that has withstood repeated testing and is accepted as being true in all cases. C. A hypothesis is a testable question developed by a scientist based on a series of observations; a scientific theory is an explanatory idea that is broad in scope and supported by the results from many experiments designed to test hypotheses. D. A hypothesis is a theory that has withstood repeated testing and is accepted as being true in all cases; a scientific theory is a scientific observation that has been repeatedly confirmed. E. None Of The Above. (C) Definition question. 8. Sodium chloride is held together by ____ bonds; Dihydrogen monoxide is held together by ____ bonds; A. Ionic; Polar covalent B. Polar covalent; Ionic C. Ionic; Nonpolar covalent D. Nonpolar covalent; Ionic E. None Of The Above. (A) Sodum cloride is NaCl or table salt. Na gives up an electron to be positively charged and Cl accepts an electron to become negatively charged. Dihydrogen monoxide is H 2, aka water. Its atoms are held together using polar covalent bonds. 9. Approximately how many hydrogen bonds does it take to yield the same strength (kJ/ mol) of a covalent bond? A. 1 B. 10 0 0 1 . C 0 0 0 1 . D E. None Of The Above. (B) This chart was shown multiple times in lecture: Strength of bonds: (kJ/mol) Covalent: 100-400 Ionic: 50-200 Hydrogen: 10-65 10._____ causes water to form droplets; ____ causes water to stick to other things. A. Adhesion; cohesion B. Surface tension; cohesion C. Surface tension; adhesion D. Cohesion; surface tension E. None Of The Above. (E) Cohesion is the ability of water to stick to itself. Adhesion is the ability of water to stick to other things. 11. A mole of sodium chloride weighs approximately 58 grams. How much sodium chloride is needed to make 4 liters of 0.5M table salt solution? A. 29 grams B. 58 grams C. 87 grams D. 116 grams E. None Of The Above. (D) 58g/mol * .5 mol/L * 4 L = 116g 12. _____ atoms give organic molecules their overall shape; _____ atoms determine the overall chemical behavior of organic molecules. A. Hydrogen; C, N, and O B. H, N, and O; carbon C. Carbon; H, N, and O D. Carbon; water E. None Of The Above. (C) Carbon is used as the skeleton of an organic molecule, H, N, O provide charge to a molecule which greatly influences their chemical behavior. 13. Why do chemical reactions tend to speed up when the temperature of the reactants is increased? What type of energy is this? A. The reactants collide more frequently; potential B. The electronegativity of the reactants is decreased; kinetic C. The specific heat is increased; free D. The heat of vaporization is decreased; covalent E. None Of The Above. (E) Heat causes molecules to move faster which is molecular kinetic energy. This results in more collisions per second and increase the likelihood of a productive reaction. 14. Which of the following statements most accurately describes the relative locations of the covalently bonded electrons in methane (CH ) and 4mmonia (NH )? 3 A. Electrons are shared unequally in both molecules. B. Electrons are shared equally in both molecules. C. Electrons are shared equally in CH 4nd unequally in NH . 3 D. Electrons are shared equally in NH 3nd unequally in CH . 4 E. None Of The Above. (C) C and H have a similar electronegativity. N is more electronegative than H. Consider the molecule above when answering questions 15 – 16. 15. The Carbon atom, attached to another carbon atom and a nitrogen, is known as the ______________ carbon. ▯ A. central B. primary C. alpha 1 # . ▯ D E. none of the above (C) the alpha carbon 16. The OH group is part of a(n) _______________ because it donates it’s ____________ion, which is accepted by the _________ atom. The entire molecule thus has ______________ charge and is known as a Zwitterion. A. aldehyde, oxygen, hydrogen, a negative B. carboxylic acid, hydrogen, oxygen, a positive C. aldehyde, hydrogen, nitrogen, no net D. carboxylic acid, hydrogen, nitrogen, a negative E. none of the above (E) The OH is part of a carboxylic acid because it donates its hydrogen ion, which is accepted by the nitrogen atom. The entire molecule thus has no net charge and is known as a Zwitterion. 17. What aspects of amino acid structure vary among different amino acids? A. the long carbon-hydrogen tails of the molecule B. the presence and location of the primary carbon atom C. the glycerol molecule that forms the backbone of the amino acid D. the components of the R-group E. both B and D (D) R-groups vary among amino acids and give different amino acids different chemical properties. ? ? A B C D 18. Consider the image above. Which of the following correctly represent the contents of boxes A – D? 1. A: N-terminus; B: C-terminus; C: acidic amino acid; D: primary structure 2. A: NH3+; B: COO-; C: peptide; D: polymer 3. A: N-terminus; B: C-terminus; C: hydrophobic amino acid; D: protein 4. A: NH3+; B: COO-; C: monomer; D: polypeptide A. 1, 2, 3 B. 2, 3, 4 C. 1, 3, 4 D. 1, 2, 4 E. 1, 2, 3, 4 (D) The amino acid in box C is aspartic acid and is hydrophilic due to its negative charge. 19. You are studying a protein that is shaped like a doughnut. The shape is a function of which level(s) of protein structure? A. tertiary only B. primary only C. secondary and tertiary only D. secondary only E. primary, secondary, and tertiary (E) Primary structure influences secondary structure which influences tertiary structure. 20. Which of the following statements are true? 1. An alpha-helix is a type of secondary structure created by hydrogen bonds formed along the backbone atoms of an amino acid chain. 2. Tertiary structures are created by ionic bonds, hydrogen bonds, sulfur bridges, hydrophobic interactions and Van der Waals forces. 3. Quaternary structure is achieved when a protein has multiple sub-units. 4. Once a protein has achieved tertiary structure, it is referred to as “folded”. A. 1,2 only B. 2,3 only C. 1,2,3 only D. 2,3,4 only E. 1,2,3,4 (E) All statements are true. 21. In cells, the activity of enzymes is often regulated by other molecules. Why is this necessary? A. because it is unlikely that all reaction products are required all of the time B. because other molecules are necessary to prevent enzymes from denaturing C. because every enzyme has multiple functions D. because all enzymes require some help from another molecule to function correctly E. because most enzymes function as trans-membrane channels (A) It is inefficient for cells to catalyze reactions when products are not required or when substrates are not present. 22. 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. allosteric activation B. allosteric deactivation C. co-factor mediated regulation D. competitive inhibition E. none of the above (D) In competitive inhibition, molecules compete for the active site of the enzyme. 23. 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 requires a cofactor to function normally. B. The protein has a quaternary structure. C. The protein’s structure is affected by temperature and pH. D. The enzyme is subject to allosteric regulation. E. none of the above (B) Enzymes composed of more than one polypeptide have quaternary structure. c. _______________ d. _______________ e. _______________ a. _______________ b. _______________ Consider the graph above when answering questions 24. 24. Which of the following represents a correct labeling of elements a-e of the graph? A. a: free energy; b: reaction progress; c: activation state; d: ∆G; e: activation ▯ ▯ energy B. a:time; b: ∆G; c: transition state; d: activation energy; e: free energy C. a: free energy; b: reaction progress; c: transition state; d: activation energy; ∆G D. a: time; b: free energy; c: activation state; d: activation energy; e: ∆G E. none of the above (C) The graph depicts free energy (y-axis) during a reaction progression (x-axis). The activation energy is the energy required to achieve the transition state, which is unstable. When the product is formed from the substrate, the change in free energy is the ∆G, which is the same whether the reaction takes place in the presence or absence of a catalytic enzyme. Consider the following paragraph and figure and answer questions 25 – 28. Since structure correlates so well with function, biochemists are constantly looking for new ways to probe the complex structure of proteins in order to understand what they do and how they do it. One of the most powerful techniques in existence today is X-ray crystallography. The main difficulty with this technique is getting the protein to crystallize. Once crystallized, the protein is bombarded with X-rays to create a pattern that can be analyzed mathematically to determine the three-dimensional structure of the protein. This analysis has been performed by Krzysztof Palczewski on the protein rhodopsin, which is a light-sensitive protein found in species ranging from ancient bacteria (archaea) to humans. The structure (schematically shown below, where each letter represents an amino acid) is characterized by a single polypeptide chain with several α-helical segments that loop back and forth across the cell membrane. Another notable feature is the disulfide bond (-S-S-) that can be seen at the bottom of the third transmembrane segment. [Figure adapted from K. Palczewski et al., Science 289 (2000): 739.] 25. If you were reading off the sequence of amino acids in the figure to a biologist friend, what should the first three letters be? A. APA B. MNG C. it doesn’t matter, the protein has no polarity or direction (B) MNG. Proteins begin at the amino (NH ) terminus and end at the carboxyl (COOH) 2 terminus. 26. Identify the location of the disulfide bond in the figure. What is the name of the amino acids that are forming this bond? A. cytosine B. glycine C. aspartic acid D. cysteine E. none of the above (
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