Rucete ✏ AP Biology In a Nutshell
2. Macromolecules — Practice Questions
This chapter explores the four major macromolecules essential for life—carbohydrates, lipids, proteins, and nucleic acids—and their structure, function, and interactions.
(Multiple Choice — Click to Reveal Answer)
1. Which of the following elements is found in all biological macromolecules?
(A) Calcium
(B) Iron
(C) Hydrogen
(D) Magnesium
Answer
(C) — Hydrogen is present in all macromolecules: carbohydrates, lipids, proteins, and nucleic acids.
2. What type of reaction forms polymers from monomers?
(A) Hydrolysis
(B) Ionic bonding
(C) Dehydration synthesis
(D) Hydrogen bonding
Answer
(C) — Dehydration synthesis removes water to link monomers into polymers.
3. Which macromolecule is primarily responsible for storing genetic information?
(A) Carbohydrate
(B) Lipid
(C) Nucleic acid
(D) Protein
Answer
(C) — DNA and RNA are nucleic acids that carry genetic instructions.
4. Which type of macromolecule includes enzymes?
(A) Protein
(B) Lipid
(C) Carbohydrate
(D) Nucleic acid
Answer
(A) — Enzymes are proteins that catalyze biochemical reactions.
5. What is a distinguishing structural feature of a saturated fatty acid?
(A) One or more double bonds between carbons
(B) Only single bonds between carbon atoms
(C) It contains nitrogen
(D) It is polar
Answer
(B) — Saturated fatty acids have only single C–C bonds, making them straight and solid at room temperature.
6. What type of bond connects amino acids in a protein’s primary structure?
(A) Peptide bond
(B) Hydrogen bond
(C) Disulfide bond
(D) Ionic bond
Answer
(A) — Peptide bonds, formed by dehydration reactions, link amino acids in a protein chain.
7. Which of the following correctly describes a nucleotide?
(A) Monomer of proteins
(B) Contains a phosphate, a sugar, and a nitrogenous base
(C) Found only in carbohydrates
(D) Nonpolar molecule with a long hydrocarbon tail
Answer
(B) — Nucleotides, the monomers of nucleic acids, contain a phosphate group, a 5-carbon sugar, and a nitrogenous base.
8. Which of the following is a polysaccharide used for energy storage in animals?
(A) Starch
(B) Cellulose
(C) Glycogen
(D) Chitin
Answer
(C) — Glycogen is the energy storage carbohydrate found in liver and muscle cells of animals.
9. Which component of an amino acid determines its identity and properties?
(A) Amino group
(B) Carboxyl group
(C) R-group (side chain)
(D) Central carbon
Answer
(C) — The R-group is unique to each amino acid and determines its chemical nature (polar, nonpolar, acidic, etc.).
10. What kind of macromolecule is cholesterol?
(A) Protein
(B) Carbohydrate
(C) Lipid
(D) Nucleic acid
Answer
(C) — Cholesterol is a steroid, which is a type of lipid.
11. What process breaks polymers into monomers by adding water?
(A) Dehydration synthesis
(B) Condensation
(C) Hydrolysis
(D) Combustion
Answer
(C) — Hydrolysis breaks covalent bonds between monomers using water.
12. Which sugar is found in RNA but not in DNA?
(A) Ribose
(B) Deoxyribose
(C) Glucose
(D) Fructose
Answer
(A) — RNA contains ribose, while DNA contains deoxyribose.
13. What is the main structural difference between saturated and unsaturated fatty acids?
(A) Presence of sulfur
(B) Saturated fatty acids contain double bonds
(C) Unsaturated fatty acids contain one or more double bonds
(D) Saturated fatty acids are hydrophilic
Answer
(C) — Unsaturated fatty acids have one or more C=C double bonds that introduce bends into the chain.
14. Which of the following is a function of proteins?
(A) Energy storage
(B) Genetic information storage
(C) Catalyzing biochemical reactions
(D) Waterproofing the skin
Answer
(C) — Many proteins act as enzymes to speed up chemical reactions in the body.
15. What level of protein structure involves hydrogen bonding between parts of the polypeptide backbone?
(A) Primary
(B) Secondary
(C) Tertiary
(D) Quaternary
Answer
(B) — Secondary structure includes alpha helices and beta sheets formed by hydrogen bonding between backbone atoms.
16. Which macromolecule is not made of repeating monomer units?
(A) Protein
(B) Lipid
(C) Carbohydrate
(D) Nucleic acid
Answer
(B) — Lipids are not polymers in the traditional sense; they are made of components like fatty acids and glycerol but not repeated monomers.
17. What kind of macromolecule is hemoglobin?
(A) Lipid
(B) Carbohydrate
(C) Protein
(D) Nucleic acid
Answer
(C) — Hemoglobin is a protein responsible for transporting oxygen in the blood.
18. Which element is found in proteins but not in carbohydrates or lipids?
(A) Carbon
(B) Hydrogen
(C) Oxygen
(D) Nitrogen
Answer
(D) — Nitrogen is a component of amino acids, which make up proteins, but not of carbohydrates or lipids.
19. Which bond is responsible for holding base pairs together in DNA?
(A) Peptide bond
(B) Ionic bond
(C) Phosphodiester bond
(D) Hydrogen bond
Answer
(D) — Hydrogen bonds hold complementary nitrogenous bases together in the double helix.
20. Which of the following is a structural polysaccharide found in plants?
(A) Glycogen
(B) Starch
(C) Cellulose
(D) Chitin
Answer
(C) — Cellulose is used for structural support in plant cell walls.
21. Which statement about phospholipids is true?
(A) They are completely hydrophobic
(B) They contain a phosphate group and two fatty acids
(C) They are a type of nucleic acid
(D) They contain peptide bonds
Answer
(B) — Phospholipids have a hydrophilic phosphate head and two hydrophobic fatty acid tails.
22. What type of macromolecule is starch?
(A) Protein
(B) Carbohydrate
(C) Lipid
(D) Nucleic acid
Answer
(B) — Starch is a polysaccharide used by plants for energy storage.
23. Which macromolecule is amphipathic and crucial in forming biological membranes?
(A) Cholesterol
(B) Phospholipid
(C) Triglyceride
(D) Glucose
Answer
(B) — Phospholipids contain both hydrophilic and hydrophobic regions, allowing them to form lipid bilayers.
24. Which type of bond links nucleotides in a nucleic acid strand?
(A) Hydrogen bond
(B) Ionic bond
(C) Peptide bond
(D) Phosphodiester bond
Answer
(D) — Phosphodiester bonds connect the sugar and phosphate groups of adjacent nucleotides in DNA or RNA.
25. What is the function of chaperonins in protein synthesis?
(A) To break down misfolded proteins
(B) To link amino acids
(C) To guide proper folding of polypeptides
(D) To synthesize RNA
Answer
(C) — Chaperonins assist in the correct folding of polypeptides into functional protein structures.
26. A researcher is analyzing a molecule made up of carbon, hydrogen, oxygen, nitrogen, and phosphorus. It is most likely a:
(A) Lipid
(B) Protein
(C) Nucleic acid
(D) Carbohydrate
Answer
(C) — Nucleic acids contain all five of these elements; proteins lack phosphorus and carbohydrates/lipids lack nitrogen.
27. Which of the following is an accurate comparison between DNA and RNA?
(A) DNA contains uracil; RNA contains thymine
(B) RNA is double-stranded; DNA is single-stranded
(C) DNA contains deoxyribose; RNA contains ribose
(D) DNA contains phospholipids; RNA contains proteins
Answer
(C) — DNA’s sugar is deoxyribose, while RNA’s sugar is ribose.
28. A scientist wants to increase the fluidity of a cell membrane. Which modification would be most effective?
(A) Decrease cholesterol concentration
(B) Increase saturated fatty acids
(C) Increase unsaturated fatty acids
(D) Increase phospholipid head size
Answer
(C) — Unsaturated fatty acids introduce kinks in tails, preventing tight packing and increasing membrane fluidity.
29. During protein folding, which of the following interactions would most likely occur in the interior of the protein structure in water?
(A) Hydrogen bonding between polar side chains
(B) Ionic bonding between charged side chains
(C) Hydrophobic interactions among nonpolar side chains
(D) Disulfide bridges between hydrophilic side chains
Answer
(C) — Nonpolar side chains cluster away from water in the interior due to hydrophobic interactions.
30. Which part of an amino acid always varies between different types of amino acids?
(A) Carboxyl group
(B) Amino group
(C) R-group
(D) Alpha carbon
Answer
(C) — The R-group (side chain) defines the specific properties of each amino acid.
31. What explains the higher melting point of DNA with a greater GC content?
(A) GC pairs are closer together
(B) GC pairs form three hydrogen bonds
(C) GC pairs form peptide bonds
(D) GC pairs are less polar
Answer
(B) — Guanine and cytosine form three hydrogen bonds (versus two for AT), requiring more energy to break.
32. A mutation changes a polar amino acid in a protein’s active site to a nonpolar one. What is the most likely result?
(A) The protein will be more stable
(B) The protein's function may be impaired
(C) The protein will denature immediately
(D) The protein will form more hydrogen bonds
Answer
(B) — Replacing a polar amino acid with a nonpolar one can disrupt interactions with substrates or the environment, possibly reducing function.
33. Which of the following best describes phosphodiester bonds?
(A) Bonds between amino acids
(B) Bonds between glucose units
(C) Bonds between nucleotides in DNA or RNA
(D) Bonds between fatty acids and glycerol
Answer
(C) — Phosphodiester bonds form the backbone of nucleic acid strands.
34. Why do saturated fatty acids tend to be solid at room temperature while unsaturated fatty acids are liquid?
(A) Saturated fats have fewer hydrogen atoms
(B) Unsaturated fats have stronger van der Waals forces
(C) Saturated fats pack tightly due to straight chains
(D) Unsaturated fats form crystals
Answer
(C) — Straight saturated chains pack closely, forming solids. Kinks in unsaturated chains prevent tight packing.
35. Which macromolecule includes monomers with nitrogenous bases?
(A) Carbohydrates
(B) Lipids
(C) Proteins
(D) Nucleic acids
Answer
(D) — Nucleotides in nucleic acids contain nitrogenous bases like adenine and guanine.
36. Describe the chemical difference between saturated and unsaturated fatty acids.
Answer
Saturated fatty acids have only single bonds between carbon atoms, resulting in straight chains. Unsaturated fatty acids contain one or more double bonds, which create kinks in the chain.
37. What is the function of phospholipids in biological membranes?
Answer
Phospholipids form the lipid bilayer of membranes, creating a barrier with hydrophilic heads facing outward and hydrophobic tails facing inward.
38. Explain why DNA with a higher GC content has a higher melting temperature.
Answer
GC base pairs form three hydrogen bonds, compared to two between AT pairs. More hydrogen bonds require more heat to break, raising the melting temperature.
39. What kind of bond joins two amino acids together during protein synthesis?
Answer
Peptide bond — A covalent bond formed through dehydration synthesis between the amino group of one amino acid and the carboxyl group of another.
40. Which level of protein structure involves interactions between R-groups of amino acids?
Answer
Tertiary structure — It results from R-group interactions, including hydrophobic forces, hydrogen bonds, ionic bonds, and disulfide bridges.
41. How does the polarity of amino acid side chains affect protein folding?
Answer
Polar side chains tend to be exposed to water (outside), while nonpolar side chains are buried inside, driving the 3D folding of the protein.
42. Name the three components of a nucleotide.
Answer
Phosphate group, five-carbon sugar (ribose or deoxyribose), and nitrogenous base (A, T, G, C, or U).
43. What feature makes phospholipids amphipathic?
Answer
They have a hydrophilic phosphate head and hydrophobic fatty acid tails, allowing them to form membranes in aqueous environments.
44. Why do enzymes typically function poorly outside their optimal pH range?
Answer
Changes in pH can disrupt hydrogen and ionic bonds that maintain enzyme shape, leading to denaturation and loss of function.
45. What kind of macromolecule are antibodies made of, and what is their function?
Answer
Proteins — Antibodies identify and neutralize foreign substances like bacteria and viruses in the immune system.
46. How do hydrolysis and dehydration reactions differ?
Answer
Dehydration joins monomers by removing water; hydrolysis breaks polymers into monomers by adding water.
47. Why is protein shape critical to its function?
Answer
Proteins must have a specific 3D shape to bind properly to other molecules and perform their biological roles.
48. Identify one structural carbohydrate and one energy storage carbohydrate in plants.
Answer
Cellulose is structural (cell wall); starch is used for energy storage.
49. What does it mean that DNA strands are antiparallel?
Answer
One strand runs 5′ to 3′, and the other runs 3′ to 5′, allowing base pairs to align and form the double helix.
50. Which macromolecule class includes enzymes and what is their role?
Answer
Proteins — Enzymes are biological catalysts that speed up chemical reactions without being consumed.