Class 9 Biology MCQs: Metabolism

MCQs (sample)

Showing 25 questions from this chapter. For a full timed test, use “Start online test”.

1. 1. What is the fuel for respiration in our body?

   • Glucose
   • Oxygen
   • Water
   • Carbon dioxide
   Answer & explanation

   Correct: Glucose

   The fuel for respiration in our body is glucose from our food.

2. 2. What is the specific part of the enzyme called where the substrate binds?

   • Active site
   • Substrate
   • Product
   • Enzyme complex
   Answer & explanation

   Correct: Active site

   The part of the enzyme where the substrate binds is called the active site.

3. 3. What is ATP commonly known as?

   • Energy currency of the cell
   • Energy storage unit
   • Energy catalyst
   • Energy transporter
   Answer & explanation

   Correct: Energy currency of the cell

   ATP is referred to as the 'energy currency' of the cell due to its role in storing and releasing energy.

4. 4. What are enzymes primarily made of?

   • Chains of amino acids
   • Carbohydrates
   • Nucleic acids
   • Lipids
   Answer & explanation

   Correct: Chains of amino acids

   Enzymes are made up of chains of amino acids folded to form globular proteins.

5. 5. What is the optimum temperature for human enzymes?

   • 36°C to 38°C
   • 20°C to 25°C
   • 40°C to 45°C
   • 30°C to 33°C
   Answer & explanation

   Correct: 36°C to 38°C

   The optimum temperature for human enzymes is between 36°C to 38°C.

6. 6. What is enzyme inhibition?

   • Interference of chemicals at the reaction site.
   • Increase in enzyme activity.
   • Conversion of substrate into products.
   • Formation of new enzymes.
   Answer & explanation

   Correct: Interference of chemicals at the reaction site.

   Enzyme inhibition is the phenomenon where enzymes are hindered in their function due to chemicals at the reaction site.

7. 7. What is the main product of photosynthesis?

   • Glucose
   • Oxygen
   • Carbon Dioxide
   • ATP
   Answer & explanation

   Correct: Glucose

   The main product of photosynthesis is glucose, which is synthesized using carbon dioxide and water.

8. 8. What is the process called when substances are converted into different substances?

   • Chemical reaction
   • Biochemical reaction
   • Metabolism
   • Photosynthesis
   Answer & explanation

   Correct: Chemical reaction

   A chemical reaction is defined as a process in which one or more substances, called reactants, are converted to one or more different substances, known as products.

9. 9. What is the process of energy production from food called?

   • Metabolism
   • Digestion
   • Respiration
   • Photosynthesis
   Answer & explanation

   Correct: Respiration

   The process by which energy is produced from food is called respiration.

10. 10. What forms when the substrate temporarily binds to the active site of an enzyme?

    • Enzyme Product (EP) complex
    • Enzyme Substrate (ES) complex
    • Active site
    • Product
    Answer & explanation

    Correct: Enzyme Substrate (ES) complex

    When the substrate binds to the active site of the enzyme, it forms the Enzyme Substrate (ES) complex.

11. 11. Which process converts ATP to ADP?

    • Hydrolysis
    • Condensation
    • Saturation
    • Evaporation
    Answer & explanation

    Correct: Hydrolysis

    ATP is converted to ADP through a process called hydrolysis.

12. 12. What term describes substances that enzymes act upon?

    • Cofactors
    • Substrates
    • Products
    • Metabolites
    Answer & explanation

    Correct: Substrates

    Enzymes act on specific molecules called substrates.

13. 13. What happens to enzymes at very high temperatures?

    • They become more active
    • They undergo denaturation
    • They speed up reactions
    • They become less sensitive to pH
    Answer & explanation

    Correct: They undergo denaturation

    At very high temperatures, the atoms of the enzyme molecule start vibrating vigorously, damaging the globular structure and active site, which is called denaturation.

14. 14. What is an inhibitor?

    • A chemical that reacts with an enzyme but does not produce products.
    • A substance that enhances enzyme activity.
    • A type of substrate.
    • A product of the enzyme reaction.
    Answer & explanation

    Correct: A chemical that reacts with an enzyme but does not produce products.

    An inhibitor is a chemical that reacts with an enzyme instead of the substrate, preventing product formation and inhibiting enzyme action.

15. 15. Which molecules are produced during the light dependent reactions of photosynthesis?

    • NADPH and ATP
    • Glucose and Oxygen
    • RuBP and 3PGA
    • H2O and CO2
    Answer & explanation

    Correct: NADPH and ATP

    The light dependent reactions produce NADPH and ATP, which are energy-rich molecules.

16. 16. What are biochemical reactions responsible for?

    • Breaking down food
    • Sustaining life of living organisms
    • Converting sunlight to energy
    • Forming complex molecules
    Answer & explanation

    Correct: Sustaining life of living organisms

    Biochemical reactions are the chemical reactions that occur in living organisms, which are essential for sustaining life.

17. 17. Which type of respiration occurs in the absence of oxygen?

    • Aerobic respiration
    • Anaerobic respiration
    • Photosynthesis
    • Cellular respiration
    Answer & explanation

    Correct: Anaerobic respiration

    Anaerobic respiration is defined as respiration in the absence of oxygen.

18. 18. According to the lock and key model, what is the nature of the active site?

    • Flexible structure
    • Rigid structure
    • Variable structure
    • Non-specific structure
    Answer & explanation

    Correct: Rigid structure

    In the lock and key model, the active site of the enzyme is a rigid structure that does not change.

19. 19. What remains in the cell after the hydrolysis of ATP?

    • ADP and inorganic phosphate
    • AMP and energy
    • Glucose and ATP
    • NADH and O2
    Answer & explanation

    Correct: ADP and inorganic phosphate

    After the hydrolysis of ATP, ADP and inorganic phosphate remain in the cell.

20. 20. What is the function of cofactors in enzymatic reactions?

    • They change the substrate structure.
    • They provide energy or act as a bridge between the enzyme and substrate.
    • They act as substrates themselves.
    • They deactivate the enzyme.
    Answer & explanation

    Correct: They provide energy or act as a bridge between the enzyme and substrate.

    Cofactors assist enzymes by acting as a bridge or providing energy for proper functioning.

21. 21. What effect does pH have on enzyme activity?

    • Increases activity at all levels
    • Reduces activity only at extreme changes
    • Affects enzyme function and has an optimum level
    • Has no effect on enzyme function
    Answer & explanation

    Correct: Affects enzyme function and has an optimum level

    pH affects enzyme function, with each enzyme performing best at a specific pH called optimum pH, and extreme changes can denature the enzyme.

22. 22. Which of the following can serve as an external factor for enzyme inhibition?

    • Poison.
    • Vitamin C.
    • Glucose.
    • Water.
    Answer & explanation

    Correct: Poison.

    Poisons are listed as external factors responsible for enzyme inhibition alongside cyanide, antibiotics, and some drugs.

23. 23. Where do the light independent reactions of photosynthesis take place?

    • Chloroplasts
    • Thylakoid membranes
    • Stroma of chloroplast
    • Photosystems
    Answer & explanation

    Correct: Stroma of chloroplast

    The light independent reactions, also known as the Calvin cycle, take place in the stroma of the chloroplast.

24. 24. Which type of metabolism breaks down complex molecules?

    • Anabolism
    • Catabolism
    • Photosynthesis
    • Cellular respiration
    Answer & explanation

    Correct: Catabolism

    Catabolism is the type of metabolism that breaks down complex molecules into simpler ones.

25. 25. What happens to pyruvic acid during alcoholic fermentation?

    • It is converted to lactic acid
    • It is converted to ethyl alcohol and carbon dioxide
    • It is released as carbon dioxide
    • It is oxidized to glucose
    Answer & explanation

    Correct: It is converted to ethyl alcohol and carbon dioxide

    During alcoholic fermentation, pyruvic acid is converted into ethyl alcohol and carbon dioxide.