Respiration — Homi Bhabha Class 9 Biology MCQs with Solutions
Free Homi Bhabha Class 9 Biology Respiration MCQs with step-by-step solutions (12 questions). Part of Life Processes. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Respiration · medium · theory
The type of respiration that takes place in the presence of oxygen is called:
A. transpiration
B. fermentation
C. anaerobic respiration
D. aerobic respiration ✓ Correct
Solution: Aerobic respiration uses oxygen and releases more energy than anaerobic respiration.
Q2 — Respiration · hard · theory
Anaerobic respiration in yeast produces carbon dioxide and:
A. water only
B. lactic acid
C. oxygen
D. ethanol (alcohol) ✓ Correct
Solution: Yeast carries out fermentation, producing ethanol and CO₂.
Q3 — Respiration · hard · theory
During vigorous exercise, the anaerobic respiration in our muscles produces:
A. carbon dioxide only
B. glucose
C. lactic acid ✓ Correct
D. ethanol
Solution: When oxygen is scarce, muscle cells form lactic acid, which causes cramps.
Q4 — Respiration · medium · theory
The organelle where most of the energy is released during respiration is the:
A. ribosome
B. nucleus
C. mitochondrion ✓ Correct
D. chloroplast
Solution: Mitochondria are the sites of aerobic respiration, releasing energy as ATP.
Q5 — Respiration · hard · theory
Which statement correctly distinguishes breathing from respiration?
A. Breathing is a physical process; respiration is a chemical process that releases energy ✓ Correct
B. They are exactly the same
C. Breathing releases energy from food
D. Respiration is only physical
Solution: Breathing is the physical exchange of gases, while respiration is the chemical breakdown of food to release energy.
Q6 — Respiration · medium · theory
Respiration releases energy by the breakdown of:
A. water
B. oxygen
C. glucose ✓ Correct
D. carbon dioxide
Solution: Glucose is oxidised during respiration to release energy stored in it.
Q7 — Respiration · hard · theory
Which of the following is TRUE about plants?
A. Plants only photosynthesise
B. Plants respire all the time, taking in oxygen and giving out carbon dioxide ✓ Correct
C. Plants respire only in sunlight
D. Plants never respire
Solution: Plants respire continuously (day and night), while photosynthesis occurs only in light.
Q8 — Respiration · easy · theory
During heavy exercise, the muscles of humans may respire without enough oxygen. The end product formed is:
A. Lactic acid ✓ Correct
B. Ethanol and carbon dioxide
C. Carbon dioxide and water
D. Only pyruvate
Solution: When oxygen is limited, muscle cells break down pyruvate anaerobically into lactic acid. Its build-up causes muscle cramps and fatigue.
Q9 — Respiration · easy · theory
In which cell organelle does aerobic respiration mainly take place?
A. Nucleus
B. Ribosome
C. Chloroplast
D. Mitochondria ✓ Correct
Solution: Mitochondria are the site of aerobic respiration, where pyruvate is broken down using oxygen to release a large amount of energy. They are called the powerhouse of the cell.
Q10 — Respiration · medium · theory
When yeast respires anaerobically (fermentation), glucose is converted mainly into:
A. Carbon dioxide and water
B. Glucose and oxygen
C. Ethanol and carbon dioxide ✓ Correct
D. Lactic acid
Solution: In yeast, anaerobic respiration (fermentation) breaks glucose into ethanol and carbon dioxide. This is used in baking and brewing.
Q11 — Respiration · medium · numerical
Aerobic respiration of one glucose molecule yields about 38 units of ATP, while anaerobic respiration yields about 2 units of ATP. About how many times more energy does aerobic respiration release per glucose?
A. 36 times
B. 40 times
C. 19 times ✓ Correct
D. 2 times
Solution: Ratio = 38 divided by 2 = 19. So aerobic respiration releases about 19 times more energy per glucose molecule than anaerobic respiration, which is why aerobic organisms are far more efficient.
Q12 — Respiration · hard · theory
Fish breathe much faster than land animals of a similar size. The BEST reason for this is:
A. The amount of oxygen dissolved in water is much lower than the oxygen available in air ✓ Correct
B. Water contains no oxygen at all
C. Fish need far more oxygen than land animals
D. Air contains less oxygen than water
Solution: The concentration of dissolved oxygen in water is much lower than the oxygen content of air. To obtain enough oxygen, fish must pass large amounts of water over their gills, so their breathing rate is high.