9 1st Weeks Exam Study Guide Answers
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1. In a single molecule of water, the two hydrogen atoms are bonded to a single oxygen atom by
polar covalent bonds.
2. The slight negative charge at one end of one water molecule is attracted to the slight positive charge of
another water molecule. What is this attraction called?
a hydrogen bond
3. Water is able to form hydrogen bonds because
the bonds that hold together the atoms in a water molecule are polar covalent bonds.
4. What determines the cohesiveness of water molecules?
hydrogen bonds
5. What do cohesion, surface tension, and adhesion have in common with reference to water?
All are properties related to hydrogen bonding.
6. Which of the following is possible due to the high surface tension of water?
A water strider can walk across the surface of a small pond.
7. Which of the following is a correct definition of a kilocalorie?
the amount of heat required to raise the temperature of 1 kg of water by 1C
8. Water's high specific heat is mainly a consequence of the
absorption and release of heat when hydrogen bonds break and form.
9. Which bonds must be broken for water to vaporize?
hydrogen bonds
10. Ice is lighter and floats in water because it is a crystalline structure in which each water molecule is bonded to
a maximum of four other water molecules by which kind of bond?
hydrogen
11. Why does ice float in liquid water?
Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water
molecules of liquid water.
The picture below illustrates a solute molecule surrounded by a hydration shell of water. Use it to answer the
following question.
____ 12. Based on your knowledge of the polarity of water molecules, the solute molecule is most likely
positively charged.
____ 13. One mole (mol) of a substance is
____ 14.
____ 15.
____ 16.
____ 17.
____ 18.
6.023 x 1023 molecules of a substance
The molecular mass of a substance expressed in grams
How many molecules of glucose (C6H2O6 molecular mass =180 daltons) would be present in one mole of
glucose?
6.02 1023
How many molecules of glycerol (C3H8O3) would be present in 1 L of a 1 M glycerol solution?
6.02 1023
Recall that when sodium chloride (NaCl) is placed in water the component atoms of the NaCl crystal
dissociate into individual sodium ions (Na+) and chloride ions (Cl-). In contrast, the atoms of covalently
bonded molecules (e.g, glucose, sucrose, glycerol) do not generally dissociate when placed in aqueous
solution. Which of the following solutions would be expected to contain the greatest concentration of particles
(molecules or ions)?
1.0 M MgCl2
The molecular mass of glucose is 180 g. To make a 1 M solution of glucose, you should do which of the
following?
Dissolve 180 g of glucose in water, and then add more water until the total volume of the
solution is 1 L.
The molecular mass of glucose (C6H12O6) is 180 g. To make a 0.5 M solution of glucose, you should do which
of the following?
Dissolve 90 g of glucose in a small volume of water, and then add more water until the
total volume of the solution is 1 L.
Use the figure below to answer the following questions:
____ 19. How many grams of the molecule in the figure above would be equal to 1 mol of the molecule?
(Carbon = 12, Oxygen = 16, Hydrogen = 1)
60
____ 20. How many grams of the molecule in the figure above would be required to make 1 L of a 0.5 M solution of
the molecule?
(Carbon = 12, Oxygen = 16, Hydrogen = 1)
30
____ 21. How many grams of the molecule in the figure above would be required to make 2.5 L of a 1 M solution of
the molecule?
(Carbon = 12, Oxygen = 16, Hydrogen = 1)
150
____ 22. Which of the following is not one of the four major groups of macromolecules found in living organisms?
glucose
____ 23. Polymers of polysaccharides, fats, and proteins are all synthesized from monomers by which process?
the removal of water (dehydration reactions)
____ 24. Which of the following best summarizes the relationship between dehydration reactions and hydrolysis?
Dehydration reactions assemble polymers, and hydrolysis breaks down polymers.
____ 25. A molecule with the chemical formula C16H32O16 is probably a
carbohydrate.
____ 26. Consider a polysaccharide consisting of 576 glucose molecules. The total hydrolysis of the polysaccharide
would result in the production of
576 glucose molecules.
____ 27. Lactose, a sugar in milk, is composed of one glucose molecule joined by a glycosidic linkage to one galactose
molecule. How is lactose classified?
as a disaccharide
____ 28. Which of the following is true of cellulose?
It is a major structural component of plant cell walls.
____ 29. Which of the following is (are) true for the class of large biological molecules known as lipids?
They are insoluble in water.
They are an important constituent of cell membranes.
They contain twice as much energy as an equivalent weight of polysaccharide.
____ 30. Triacylglycerol is a
lipid made with three fatty acids and glycerol.
____ 31. Saturated fatty acids
have a higher ratio of hydrogen to carbon than do unsaturated fatty acids.
____ 32. What is the molecule illustrated in the figure below?
a saturated acid
____ fatty 33. The molecule shown in the figure below is a
unsaturated fatty acid.
____ 34. What is the structure shown in the figure below?
steroid molecule
____ 35. A polypeptide can best be described as a
polymer of amino acids.
____ 36. The 20 different amino acids found in polypeptides exhibit different chemical and physical properties because
of different
side chains (R groups).
____ 37. The chemical reaction illustrated in the figure below results in the formation of a (an)
peptide bond.
____ 38. Upon chemical analysis, a particular protein was found to contain 556 amino acids. How many peptide bonds
are present in this protein?
555
Use the figure below to answer the following questions.
____ 39. At which bond would water need to be added to achieve hydrolysis of the peptide, back to its component
amino acid?
Bond C
____ 40. Which bond is closest to the N-terminus of the molecule?
Bond A
____ 41. Which bond is closest to the C-terminus of the molecule?
Bond E
____ 42. Which of the following describe(s) some aspect of metabolism?
synthesis of macromolecules
breakdown of macromolecules
control of enzyme activity
____ 43. Which of the following statements correctly describe(s) catabolic pathways?
They release energy as they degrade polymers to monomers.
____ 44. Which of the following is (are) true for anabolic pathways?
They are highly regulated sequences of chemical reactions.
They consume energy to build up polymers from monomers.
____ 45. Which of the following is a statement of the first law of thermodynamics?
Energy cannot be created or destroyed.
____ 46. Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism.
How does this relate to the second law of thermodynamics?
As a consequence of growing, organisms create more disorder in their environment than
the decrease in entropy associated with their growth.
____ 47. Whenever energy is transformed, there is always an increase in the
entropy of the universe.
____ 48. Which of the following statements is a logical consequence of the second law of thermodynamics?
Every chemical reaction must increase the total entropy of the universe.
____ 49. Which of the following types of reactions would decrease the entropy within a cell?
dehydration reactions
____ 50. The mathematical expression for the change in free energy of a system is: G = H - T S. Which of the
following is (are) incorrect?
H is the change in enthalpy, the energy available to do work.
____ 51. What is the change in free energy of a system at chemical equilibrium?
no net change
____ 52. Which of the following is true for all exergonic reactions?
The reaction proceeds with a net release of free energy.
____ 53. Chemical equilibrium is relatively rare in living cells. Which of the following could be an example of a
reaction at chemical equilibrium in a cell?
a chemical reaction in which both the reactants and products are only used in a metabolic
pathway that is completely inactive
____ 54. A chemical reaction that has a positive G is correctly described as
endergonic.
____ 55. Why is ATP an important molecule in metabolism?
It provides energy coupling between exergonic and endergonic reactions.
____ 56. When 10,000 molecules of ATP are hydrolyzed to ADP and in a test tube, about twice as much heat is
liberated as when a cell hydrolyzes the same amount of ATP. Which of the following is the best explanation
for this observation?
Cells convert some of the energy of ATP hydrolysis into other forms of energy besides
heat.
____ 57. ATP generally energizes a cellular process by
coupling free energy released by ATP hydrolysis to free energy needed by other reactions.
____ 58. What term is used to describe the transfer of free energy from catabolic pathways to anabolic pathways?
energy coupling
____ 59. How can one increase the rate of a chemical reaction?
Add a catalyst.
____ 60. Reactants capable of interacting to form products in a chemical reaction must first overcome a
thermodynamic barrier known as the reaction's
activation energy.
____ 61. A solution of starch at room temperature does not readily decompose to form a solution of simple sugars
because
the activation energy barrier for this reaction cannot be surmounted.
____ 62. An enzyme catalyzes a reaction by
lowering the energy of activation of a reaction.
Refer to the figure below to answer the following questions.
____ 63. Which curve represents the behavior of an enzyme taken from a bacterium that lives in hot springs at
temperatures of 70C or higher?
curve 3
____ 64. Which curve was most likely generated from analysis of an enzyme from a human stomach where conditions
are strongly acid?
curve 4
____ 65. Which curve was most likely generated from an enzyme that requires a cofactor?
It is not possible to determine whether an enzyme requires a cofactor from these data.
____ 66. As temperature decreases, the rate of an enzyme-catalyzed reaction also decreases. Which of the following
explain(s) why this occurs?
Fewer substrates have sufficient energy to get over the activation energy barrier.
Motion in the active site of the enzyme is slowed, thus slowing the catalysis of the
enzyme.