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Quiz Chapter 4: Chemical Composition in Cells

10 questions · Form 4 Biology Bab 4: Chemical Composition in Cells

Question 1 of 10Score: 0

What forms the structural backbone of a single polynucleotide strand in DNA?

Full Question List & Answer Key

Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.

1. What forms the structural backbone of a single polynucleotide strand in DNA?

  1. A. Alternating hydrogen and peptide bonds
  2. B. Complementary nitrogenous base pairs
  3. C. Alternating phosphate groups and pentose sugars linked by phosphodiester bonds
  4. D. Fatty acid chains bound to glycerol
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Answer: C

The DNA strand backbone consists of repeating sugar-phosphate units linked covalently via phosphodiester bonds.

2. What type of bond joins two monosaccharide molecules together during a condensation reaction?

  1. A. Peptide bond
  2. B. Phosphodiester bond
  3. C. Glycosidic bond
  4. D. Hydrogen bond
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Answer: C

A covalent glycosidic bond forms between hydroxyl groups of two monosaccharides during condensation.

3. How do saturated fatty acids differ structurally from unsaturated fatty acids?

  1. A. Saturated fatty acids contain double bonds between carbon atoms (C=C).
  2. B. Saturated fatty acids have single carbon-carbon bonds (C-C) and maximum hydrogen atoms.
  3. C. Unsaturated fatty acids have straight chains and high melting points.
  4. D. Saturated fatty acids are liquid at room temperature.
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Answer: B

Saturated fatty acids lack C=C double bonds, containing maximum hydrogen atoms bonded to carbon chains.

4. Which of the following disaccharides is classified as a NON-REDUCING sugar?

  1. A. Maltose
  2. B. Sucrose
  3. C. Lactose
  4. D. Cellobiose
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Answer: B

Sucrose is the only common disaccharide that does not reduce Benedict's solution because its reducing aldehyde and ketone groups are involved in the glycosidic bond.

5. Hemoglobin consists of four interconnected polypeptide subunits. What structural level of protein organization does this represent?

  1. A. Primary structure
  2. B. Secondary structure
  3. C. Tertiary structure
  4. D. Quaternary structure
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Answer: D

Quaternary structure describes proteins containing two or more polypeptide chains joined into a single functional unit.

6. Why is cellulose impossible for humans to digest, yet essential in the human diet?

  1. A. Humans lack the cellulase enzyme; cellulose acts as dietary fiber to prevent constipation.
  2. B. Cellulose poisons digestive enzymes.
  3. C. Cellulose dissolves instantly in stomach acid without absorption.
  4. D. Cellulose is absorbed directly without digestion.
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Answer: A

Humans do not produce cellulase to digest beta-glycosidic bonds in cellulose, but it provides essential dietary roughage to stimulate peristalsis.

7. Which property of water allows xylem vessels to transport water continuously from roots to leaves without breaking the water column?

  1. A. High specific heat capacity
  2. B. Low viscosity
  3. C. Cohesive and adhesive forces producing capillary action
  4. D. Maximum density at 4°C
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Answer: C

Cohesion (water molecules sticking together) and adhesion (water sticking to xylem cellulose walls) generate capillary action, sustaining continuous transpiration streams.

8. Which component of a nucleotide differs between a DNA strand and an RNA strand?

  1. A. Phosphate group
  2. B. Pentose sugar and nitrogenous bases
  3. C. Ester bond type
  4. D. Carboxyl group
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Answer: B

DNA contains deoxyribose sugar and Thymine, whereas RNA contains ribose sugar and Uracil.

9. Which of the following organic compounds is composed of carbon, hydrogen, oxygen, nitrogen, and sulfur?

  1. A. Carbohydrate
  2. B. Lipid
  3. C. Protein
  4. D. Nucleic acid
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Answer: C

Proteins contain amino acids, some of which (like cysteine and methionine) possess sulfur atoms.

10. The condensation of one glycerol molecule with three fatty acid molecules produces a triglyceride and how many water molecules?

  1. A. 1
  2. B. 2
  3. C. 3
  4. D. 4
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Answer: C

Forming three ester bonds between glycerol and three fatty acid chains releases 3 molecules of water in a condensation reaction.

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