Biochemistry Basics Quiz

Grade 12 · Science · Quiz

Test your knowledge of macromolecules, enzyme kinetics, cellular respiration, and molecular biology fundamentals.

Questions

1. Which type of bond links amino acids together to form a polypeptide chain?

   1. Hydrogen bond
   2. Ionic bond
   3. Peptide bond
   4. Disulfide bond
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   Answer: Peptide bond

   Peptide bonds form between the carboxyl group (-COOH) of one amino acid and the amino group (-NH₂) of the next through a dehydration synthesis reaction.

2. An enzyme's active site shape is altered by extreme heat. This process is called:

   1. Hydrolysis
   2. Denaturation
   3. Phosphorylation
   4. Transcription
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   Answer: Denaturation

   Denaturation is the loss of a protein's three-dimensional structure due to heat, pH changes, or chemicals. The active site changes shape, rendering the enzyme non-functional.

3. ATP (adenosine triphosphate) stores energy in its phosphate bonds and releases it when a phosphate group is removed.

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   Answer: True

   ATP stores chemical energy in its high-energy phosphoanhydride bonds between phosphate groups. Hydrolysis of the terminal phosphate (ATP → ADP + Pᵢ) releases energy for cellular work.

4. Which macromolecule serves as the primary long-term energy storage molecule in animals?

   1. Proteins
   2. Carbohydrates
   3. Nucleic acids
   4. Lipids
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   Answer: Lipids

   Lipids (specifically triglycerides/fats) are the primary long-term energy storage in animals — they yield more than twice the energy per gram compared to carbohydrates.

5. Where does the Krebs cycle (citric acid cycle) take place in the cell?

   1. Cytoplasm
   2. Nucleus
   3. Mitochondrial matrix
   4. Endoplasmic reticulum
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   Answer: Mitochondrial matrix

   The Krebs cycle occurs in the mitochondrial matrix. Pyruvate from glycolysis is converted to acetyl-CoA and fed into this cycle to produce NADH, FADH₂, and CO₂.

6. The monomer unit of DNA and RNA is called a ___.

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   Answer: nucleotide

   Nucleotides are the monomers of nucleic acids. Each consists of a nitrogenous base, a five-carbon sugar (deoxyribose in DNA, ribose in RNA), and a phosphate group.

7. A competitive inhibitor of an enzyme:

   1. Permanently destroys the active site
   2. Binds the active site and blocks substrate entry
   3. Changes the shape of the allosteric site only
   4. Increases the enzyme's optimal temperature
   Show answer

   Answer: Binds the active site and blocks substrate entry

   A competitive inhibitor competes directly with the substrate for the enzyme's active site. Its effect can be overcome by increasing substrate concentration.

8. Glycolysis produces a net gain of how many ATP molecules per glucose molecule?

   1. 2
   2. 4
   3. 32
   4. 36
   Show answer

   Answer: 2

   Glycolysis generates 4 ATP total but uses 2 ATP to start, for a net gain of 2 ATP. It also produces 2 NADH and 2 pyruvate per glucose molecule.

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