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Quiz Chapter 4: Chemical Composition in Cells

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

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Full Question List & Answer Key

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

1. Which bond stabilizes the alpha-helix and beta-pleated sheet in the secondary structure of proteins?

  1. A. Peptide bond
  2. B. Hydrogen bond
  3. C. Disulfide bridge
  4. D. Ionic bond
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Answer: B

Hydrogen bonds forming between the C=O and N-H groups of the polypeptide backbone stabilize secondary protein structures.

2. Why does water have a high specific heat capacity (4.2 kJ kg-1 °C-1?

  1. A. Oxygen and hydrogen atoms share electrons equally.
  2. B. Energy is required to break numerous hydrogen bonds before temperature rises.
  3. C. Water molecules are linked by strong covalent ester bonds.
  4. D. Water contains heavy mineral salts.
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Answer: B

A large amount of thermal energy is absorbed to break hydrogen bonds between water molecules before kinetic energy and temperature increase.

3. 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.

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. In a DNA molecule, if 30% of the nitrogenous bases are Guanine (G), what percentage of the bases will be Thymine (T)?

  1. A. 30%
  2. B. 20%
  3. C. 40%
  4. D. 60%
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Answer: B

According to Chargaff's rules, G = C (30% + 30% = 60%). The remaining 40% is split equally between A and T (40% / 2 = 20% Thymine).

6. 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.

7. 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.

8. 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.

9. Which organic molecule forms the structural cuticle layer on the epidermis of leaves to minimize transpiration water loss?

  1. A. Phospholipid
  2. B. Wax
  3. C. Steroid
  4. D. Cellulose
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Answer: B

Waxes are hydrophobic lipids that provide a waterproof barrier on plant leaves and fruits.

10. 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.

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