E. Lipids are hydrophobic (nonpolar) and insoluble in water, whereas simple carbohydrates are hydrophilic (polar) and dissolve easily in water.
Correct: Options A, D, and E. A is true because lipids have high C-H ratios yielding 9 kcal/g compared to 4 kcal/g in carbohydrates. D is true because cellulose is structural and phospholipids self-assemble into a barrier. E is true because polar -OH groups make carbs highly hydrophilic, while lipids lack oxygen and are nonpolar. Distractors: B is false because amino acids define proteins. C is false because starch is an energy storage polymer, not a structural one.
Unit: Cellular Biochemistry Page 1 of 3 (Answer Key) Standards Code: LS1-1
Bond Builders Answer Key Teacher Copy
Q3 Multiple Choice
Enzymes are specialized proteins. High temperatures or extreme pH can disrupt hydrogen bonds holding secondary and tertiary structures.
What is the direct functional consequence of this structural disruption?
1. Active State
S
Active
2. Denatured State
S
Deformed
A The enzyme catalyzes reactions faster due to increased flexibility.
The enzyme can no longer bind its substrate because its active site shape has altered.
C The enzyme transforms structurally into a lipid to protect the cell membrane.
D The primary structure immediately disassembles into individual free nitrogen bases.
Correct: Option B. 3D tertiary structure dictates enzyme active site shape. High temperatures break weak hydrogen bonds causing denaturation, destroying active site geometry and blocking substrate attachment. Distractors: A is wrong as distorted sites halt reaction catalysis. C is false because proteins cannot convert into lipids. D is false because covalent peptide bonds are rarely broken by denaturation, and nitrogen bases belong to nucleic acids, not proteins.
Q4 Multiple Select
Correct: A, B, C
The structural monomer of a nucleic acid is the nucleotide, represented on the right.
Which THREE statements correctly describe the monomer or its polymer?
1
2
3
1:Phos 2:Sug 3:Base
A. Structure 3 represents a nitrogenous base, which is variable and dictates genetic code.
B. Structure 2 represents a deoxyribose pentose sugar in DNA, and a ribose sugar in RNA.
C. Individual monomer nucleotides are assembled together by covalent phosphodiester bonds to construct the nucleic acid backbone.
D. (Incorrect) The phosphate group (Structure 1) contains high-energy peptide bonds that are broken to release kinetic energy during DNA replication.
E. (Incorrect) DNA contains single-stranded strands stabilized exclusively by disulfide bridges between phosphate groups.
Correct: Options A, B, and C. A is true because variable nitrogenous bases carry sequence code. B is true because DNA utilizes deoxyribose sugar while RNA uses ribose. C is true because strong covalent phosphodiester bonds connect sugars and phosphates to shield bases. Distractors: D is false because peptide bonds belong to proteins, and E is false because DNA is double-stranded and stabilized by base hydrogen-bonding.
Unit: Cellular Biochemistry Page 2 of 3 (Answer Key) Standards Code: LS1-1
Bond Builders Answer Key Teacher Copy
Q5 Multiple Choice
Analyze the laboratory chemical indicator results to determine the composition of the unknown organic solution.
| Test | Chemical Indicator | Negative Color | Positive Control Color | Unknown Result |
|---|---|---|---|---|
| Test A | Iodine Solution (Starch) | Amber / Yellow | Dark Blue-Black | Amber (Negative) |
| Test B | Biuret Reagent (Protein) | Light Blue | Deep Violet | Deep Violet (POSITIVE) |
| Test C | Benedict's Solution (Glucose) | Light Blue | Orange-Red (Heat) | Light Blue (Negative) |
A A complex starch (polysaccharide)
B A simple reducing sugar (monosaccharide)
An enzyme or structural polypeptide protein
D A hydrophobic neutral lipid (triglyceride)
Correct: Option C. Biuret reagent detects active peptide bonds within proteins, changing from blue to deep violet (Test B). Because enzymes are functional biological catalyst proteins, Option C is the accurate match. Distractors: A is false because Iodine remained amber (negative for starch); B is false because Benedict's remained blue (negative for glucose); D is false because Biuret does not identify neutral lipid structures.
Q6 Multiple Select
Correct: A, B
Identify membrane macromolecule roles. Which TWO statements correctly pair a membrane macromolecule with its specialized biological function?
A. Phospholipids (lipids) arrange into a hydrophobic bilayer, forming a barrier that controls the movement of large or charged water-soluble particles.
B. Carbohydrate chains (glycoproteins) act as cell surface identification markers to facilitate intercellular signaling and immune recognition.
C. (Incorrect) Nucleic acids (DNA) embed inside the bilayer hydrophobic core to directly pump ions against their concentration gradient.
D. (Incorrect) Proteins dissolve structurally into cholesterol lipids to fully lock the outer lipid bilayer in place, eliminating cell wall flexibility.
Correct: Options A and B. A is true because nonpolar fatty acid tails form an impenetrable barrier to hydrophilic ions. B is true because branching oligosaccharides serve as cell identification signatures. Distractors: C is false because nucleic acids contain gene instructions and are localized in the nucleus, never active membrane pumps (which are proteins). D is false because cholesterol controls membrane fluidity and temperature-stabilization, rather than fully solidifying it.
Unit: Cellular Biochemistry Page 3 of 3 (Answer Key) Standards Code: LS1-1
