biochemistry review 2
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Chapter 3 The Chemistry of Organic Molecules
Multiple Choice Questions
1. Saturated fatty acids and unsaturated fatty acids differ from each other in which of the following ways? A) They may have different numbers of carbons in their chains. B) The consistency at room temperature is different. C) For equal length chains they have a different number of hydrogens present. D) They differ in whether or not they have double-bonded carbon atoms. E) All of the choices are differences between saturated and unsaturated fatty acids
Answer: E
2. Which of the following would NOT be a molecule used for storage? A) starch B) fat C) glycogen D) chitin E) oil
Answer: D
3. The lipids of the cell membrane and the lipids found in butter and vegetable oil differ in which of the following? A) the number of fatty acids attached to the glycerol molecule B) the type of glycerol molecule C) the carbon to carbon bonds D) lipids of the cell membrane do not have hydrophobic sections of the molecule E) the number of glycerol molecules
Answer: A
4. Which of the following is NOT one of the four most common elements found in living organisms? A) hydrogen B) oxygen C) carbon D) sulfur E) nitrogen
Answer: D
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Chapter 3 The Chemistry of Organic Molecules
5. Organic molecules are those that contain at least A) carbon. B) carbon and oxygen. C) carbon and hydrogen. D) carbon, oxygen, and hydrogen. E) carbon and nitrogen
Answer: C
6. The differences between organic and inorganic molecules do not follow simple absolute rules. However, most organic molecules are associated with living organisms. Which of the following statements does NOT correspond to the general distinctions between these types of molecules? A) Carbon dioxide (CO2) lacks hydrogen atoms found in organic molecules. B) Formaldehyde (CH2O) is a small molecule compared to most organic molecules. C) Salt (Na+Cl-) is not an organic molecule but is important to the life of many
organisms. D) Because they are in living organisms, organic carbon atoms are different from the
inorganic carbon atoms forming the molecular structure of soot or a diamond. E) Carbon compounds are much more complex and abundant than inorganic
compounds
Answer: D
7. Which is NOT true of hydrocarbons? A) they are composed of carbon and hydrogen atom B) they may have single, double or triple-bonded carbon atoms C) they form chains or rings D) they may contain oxygen and nitrogen atoms E) they store energy in their carbon to carbon bonds
Answer: D
8. What term is used for molecules that have identical molecular formulas but the atoms in each molecule are arranged differently? A) isotope B) isomer C) homomolecules D) organic E) balanced
Answer: B
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Chapter 3 The Chemistry of Organic Molecules
9. What term is based on the Greek root words for "equal" and "part"? A) isotope B) isomer C) homomolecules D) homotope E) hydrophilic
Answer: B
10. Which is NOT an isomer of the other three? A) glucose B) ribose C) fructose D) galactose E) they are all isomers of each other
Answer: B
11. Glucose (C6H12O6) can exist as both an open-chain form and a closed-ring form. Before 1900, glucose was only thought to occur as an open chain. Now we know that over 99 percent of the time, glucose occurs in the closed-ring form. What possible difference between these forms would give chemists a clue that the open-chain form was not present? A) Open-chain molecules can form polymers and glucose does not. B) Only open-chain forms can undergo condensation, which does not occur with
glucose. C) An open chain presents ends with functional groups (in this case aldehyde), and
glucose failed to undergo typical aldehyde reactions; a phenomenon that could be explained by having no end functional group in a ring structure.
D) Because glucose is solid at room temperature, it must have saturated hydrocarbon chains.
E) Glucose could not be "denatured" so it must be a tight chain.
Answer: C
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Chapter 3 The Chemistry of Organic Molecules
12. Both glyceraldehyde and dihydroxyacetone have the molecular formula C3H6O3. However, the double-bonded oxygen in glyceraldehyde is attached to the end carbon while the dihydroxyacetone molecule has the double-bonded oxygen bonded to the middle carbon. A) These are isotopes and they will eventually decay to become the same stable
molecule. B) These are isomers and therefore have exactly the same chemical properties. C) Both are hydrophobic hydrocarbons. D) These molecules have different functional groups and are likely hydrophilic. E) All of the choices are true.
Answer: D
13. A polysaccharide is a polymer made up of which kind of monomers? A) simple sugars B) amino acids C) nucleotides D) alternating sugar and phosphate groups E) fatty acids and glycerol
Answer: A
14. A lipid is a polymer made up of which kind of monomers? A) glucose or modified glucose molecules B) amino acids C) nucleotides D) alternating sugar and phosphate groups E) fatty acids and glycerol
Answer: E
15. A dehydration reaction can also be called a _________ reaction since it forms water. A) a condensation B) a hydrolysis C) an isomeric D) an energy-releasing E) monomer formation
Answer: A
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Chapter 3 The Chemistry of Organic Molecules
16. Which pair are both structural carbohydrate molecules? A) starch and glycogen B) starch and cellulose C) glycogen and cellulose D) cellulose and chitin E) glycogen and chitin
Answer: D
17. Which carbohydrate is found in the cell walls of plants? A) starch B) chitin C) cellulose D) glycogen E) glycerol
Answer: C
18. Which carbohydrate is used in the liver for energy storage? A) starch B) chitin C) cellulose D) glycogen E) glycerol
Answer: D
19. Which carbohydrate is found in the exoskeleton of insects and crabs? A) starch B) chitin C) cellulose D) glycogen E) glycerol
Answer: B
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Chapter 3 The Chemistry of Organic Molecules
20. Which lipid does NOT contain at least some subunits similar to those in the others? A) steroids B) neutral fats C) waxes D) phospholipids E) all of these contain similar subunits
Answer: A
21. Which of the following lipids forms a bilayer between two watery regions, such as in the plasma membrane of a cell? A) steroids B) neutral fats C) waxes D) phospholipids E) cellulose
Answer: D
22. Cholesterol belongs to which of the following groups? A) steroids B) neutral fats C) waxes D) phospholipids E) polysaccharides
Answer: A
23. If an animal needed to store energy for long-term use, but not be encumbered with the weight of extra tissue, which is the best molecule for storage? A) fructose and glucose in the form of honey B) fat molecules C) complex cellulose molecules D) starch E) glycogen with extensive side branches of glucose
Answer: B
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Chapter 3 The Chemistry of Organic Molecules
24. What term is based on the Greek root words for "light" and "fat"? A) steroid B) glycogen C) carbohydrate D) cellulose E) phospholipid
Answer: E
25. A protein is a polymer made up of which kind of monomers? A) glucose or modified glucose molecules B) amino acids C) nucleotides D) alternating sugar and phosphate groups E) fatty acids and glycerol
Answer: B
26. A peptide bond is found in which type of biological molecule? A) carbohydrate B) lipid C) nucleic acid D) protein E) hydrocarbon
Answer: D
27. The alpha helix and beta sheet are found at which level of protein organization? A) primary structure B) secondary structure C) tertiary structure D) quaternary structure E) these structures are found at all levels
Answer: B
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Chapter 3 The Chemistry of Organic Molecules
28. After eating eggs for breakfast, you return in the evening, dunk the dirty dishes in water, and notice the yellow streaks remain "dried on." However, after soaking awhile, the complex of various egg yolk molecules easily "washes off." What has happened? A) soaking in water eventually resulted in condensation reactions where water broke
these bonds. B) soaking in water eventually resulted in hydrolysis reactions where water broke
these bonds. C) The egg monomers were fused to become one polymer, which was easily
dissolved by water back into monomers. D) The presence or absence of water changes the molecules from hydrophilic to
hydrophobic respectively. E) The addition of water converted organic molecules into inorganic molecules.
Answer: B
29. Below freezing and above boiling, cells are unable to function as "liquid machinery." However, most organisms' cells are still limited from functioning throughout this full range of liquid temperatures. At the molecular level in different organisms, cells' ability to vary in their tolerance to temperature, etc., is most closely related to variation in A) enzyme activity and protein denaturation. B) ATP efficiency. C) ability to form glucose polymers. D) replication of nucleic acids. E) extent of saturation of fatty acids.
Answer: A
30. A nucleic acid is a polymer made up of which kind of monomers? A) amino acids B) nucleotides C) glucose or modified glucose molecules D) alternating sugar and phosphate groups E) fatty acids and glycerol
Answer: B
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Chapter 3 The Chemistry of Organic Molecules
31. Which of these statements is NOT true about DNA? A) It is the genetic material of the cell. B) It forms a double helix. C) Adenine pairs with thymine and guanine pairs with cytosine. D) It contains the sugar ribose. E) The sugar and phosphate groups form the backbone of the molecule.
Answer: D
32. Fish sperm consists mostly of the male fish's DNA. If we tested a sample chemically, we should find relatively high amounts of A) nitrogenous bases, sugar, and phosphate groups. B) phospholipids and steroids. C) amino acids and unsaturated fats. D) triglycerides and ATP. E) globular proteins and stored fats.
Answer: A
33. Which statement is true about RNA? A) It contains adenine paired to thymine. B) One of the bases from DNA is replaced by uracil. C) It contains the sugar deoxyribose. D) Its nucleotides contain twice as many phosphate groups as DNA's nucleotides. E) It is a double-stranded molecule.
Answer: B
34. A molecule is chemically determined to have ionic bonding and a small number of atoms. This molecule is A) inorganic in nature and most probably a part of non-living matter. B) organic and associated with living matter. C) hydrophobic. D) an isotope. E) all of these
Answer: A
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Chapter 3 The Chemistry of Organic Molecules
35. The diversity of organic molecules is due to all of the following EXCEPT the fact that A) carbon needs four electrons to complete its outer shell. B) carbon can form single and double bonds with itself and other elements. C) organic molecules always contain ionic bonds. D) carbon can bond with as many as four other elements. E) organic compounds often form isomers
Answer: C
36. The reactivity of an organic molecule is primarily dependent upon ____________of the molecule. A) the carbon skeleton B) the attached functional groups such as an hydroxyl group C) the isomer D) the number of carbon atoms in the molecule E) All of the choices are correct.
Answer: B
37. Polymers are A) large organic molecules linking together repeating subunits of the same type called
monomers. B) found in proteins, carbohydrates, and nucleic acids. C) due to a dehydration reaction. D) often very long molecules due to the number of subunits E) All of the choices are correct.
Answer: E
38. Which of the following is NOT a biologically active polymer? A) starch B) collagen C) water D) DNA E) glycogen
Answer: C
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Chapter 3 The Chemistry of Organic Molecules
39. Fats, oils, and steroids are A) proteins. B) nucleic acids. C) polysaccharides. D) lipids. E) carbohydrates
Answer: D
40. A saturated fat is A) solid at room temperature. B) has fatty acids with no double bonds between the carbon atoms. C) is almost always of animal origin. D) holding the maximum number of hyrdogens possible E) All of the choices are correct.
Answer: E
Use the following to answer questions 41-43:
41. The two molecules on the left side of the above equation are A) simple sugars B) fatty acids C) amino acids D) lipids E) proteins
Answer: C
42. What type of bond is formed between the two molecules? A) disaccharide bond B) peptide bond C) disulfide bond D) hydrogen bond E) ionic bond
Answer: B
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Chapter 3 The Chemistry of Organic Molecules
43. If the reaction were to proceed from left to right, this would be an example of what type of reaction? A) hydrolysis B) dehydration C) substitution D) degradation E) none of these
Answer: B
Use the following to answer questions 44-46:
44. The above molecule represents the basic structure for which of the following? A) amino acid B) monosaccharide C) steroid D) nucleotide E) triglyceride
Answer: D
45. This molecule represents a monomer of which group of macromolecules? A) proteins B) polysaccharides C) lipids D) steroids E) nucleic acids
Answer: E
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Chapter 3 The Chemistry of Organic Molecules
46. If the 2 carbon has an -OH group attached to it, the molecule would be A) glucose B) sucrose C) ribose D) deoxyribose E) fructose
Answer: C
Essay Questions
47. Describe the unique qualities of phospholipids and how this molecule must have been essential to the formation of the earliest life forms.
Answer: The fatty acid “tails” and the phosphate “head” give the phospholipids the dual nature of being both hydrophobic at one end (the long nonpolar tails) and hydrophilic at the other (the polar head). This dual nature would have made possible the formation of the first cell membranes. As phospholipids formed in the original “organic soup”, the hydrophobic tails would turn inward toward each other to exclude water and the hydrophobic heads would have turned outward to face the water. This would have produced the first lipid bilayer and enclosed the first molecules in a primitive cell membrane.
48. Most scientists agree that life could not have truly begun until proteins developed in the early earth's environment. Describe four essential roles proteins play in maintaining and supporting living organisms.
Answer: Homeostasis--proteins form the channels in the lipid bilayer that allow the movement of materials in and out of the cell which is essential to maintaining homeostasis. Some hormones are proteins which regulate homeostasis.Enzymes catalyze the many reactions that must occur to maintain life including the reactions necessary for energy utilization.Structural uses- including building muscle in animals for movement.Communication between cells is essential to multicellular organisms. Communication is made possible by the signal molecules and protein receptor molecule on cell membranes.Immune systems from simple to complex rely on an organism's ability to recognize “non-self” proteins and to destroy them with antibodies (which are also proteins).Other answers involving functional or structural proteins.
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Chapter 3 The Chemistry of Organic Molecules
49. Carbon is a relatively unreactive atom and yet it is used to build countless compounds, many of which are necessary for the existence of life itself. a. What characteristic of carbon and its compounds account for the huge diversity of
organic compounds?b. List the categories of essential biochemical compounds, give an example of a each
and discuss that example's importance to life.
Answer: a. Forms up to four bonds at once, each can be with a different element.
Can bond with itself to form long chains. Each additional carbon is a different compoundCan form ring compoundsCan form single, double, triple bonds with itselfCan form isomers
b. Carbohydrates--such as glucose for energy (or any other structural or functional carbohydrate)Proteins--any functional or structural example (e.g. enzymes needed for catalysts)Lipids--steroids as hormones, triglycerides for energy storage, etc.
Nuclei Acids- DNA for information storage or RNA for protein production
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