Cellular Respiration — Practice · Grade 10 Science

Chapter: Matter & Energy in Living Systems

What this practice covers

By the end of Cellular Respiration you should be able to:

10 questions, multiple choice, numeric and written answer, each with a worked explanation.

Vocabulary used: glycolysis, citric acid cycle, oxidative phosphorylation, fermentation, aerobic respiration.

Problem 1

Which pair are the reactants of cellular respiration?
  1. Carbon dioxide and water
  2. ATP and sunlight
  3. Glucose and carbon dioxide
  4. Glucose and oxygen
Answer and explanation

Glucose and oxygen

Cellular respiration breaks down glucose using oxygen, producing carbon dioxide and water: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O.

Problem 2

Most of a cell's ATP from aerobic respiration is produced in the
  1. electron transport chain on the inner mitochondrial membrane
  2. cytoplasm during glycolysis
  3. nucleus
  4. ribosomes
Answer and explanation

electron transport chain on the inner mitochondrial membrane

Oxidative phosphorylation coupled to electron transport makes most of the ATP in this eukaryotic model.

Problem 3

How many ATP molecules does glycolysis produce as a NET gain from one glucose?
Answer and explanation

2 ATP

Glycolysis makes 4 ATP but spends 2 to get started, for a net gain of 2 ATP.

Problem 4

Using model yields of 30 ATP per glucose aerobically and 2 from glycolysis supported by fermentation, how many times as much ATP is obtained aerobically?
Answer and explanation

15 times

30 ÷ 2 = 15 under the stated model.

Problem 5

Explain why you breathe faster during hard exercise, in terms of what the electron transport chain needs and what it produces.
Answer and explanation

Exercise raises demand for ATP and material transport. Oxygen supports the end of electron transport, while CO₂ is produced during pyruvate processing and the citric acid cycle. Ventilation and circulation help meet those demands.

Problem 6

Why can a prokaryote obtain energy by respiration without mitochondria? Explain the reasoning in your own words.
Answer and explanation

Mitochondria are the eukaryotic compartment, not a universal requirement for respiration.

Respiration requires linked biochemical pathways and suitable membranes.

Prokaryotes can use their cell membrane for relevant electron-transport processes.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 7

Why can fermentation help glycolysis continue when oxygen-dependent pathways are unavailable? Show the reasoning, not just the conclusion.
Hints

Atoms and energy must be accounted for separately.

Answer and explanation

It regenerates NAD⁺ needed for glycolysis, with products depending on the organism/pathway.

Problem 8

Does anaerobic metabolism always produce the same amount of ATP as aerobic respiration?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

No. Yields and pathways differ; simple fermentation typically yields much less ATP per glucose than aerobic respiration.

Problem 9

Fermentation can keep glycolysis supplied with a required carrierFermentation can keep glycolysis supplied with a required carrierGlycolysisuses NAD⁺Fermentationregenerates NAD⁺Net glycolytic ATP in the supplied glucose model: 2 ATP.Fermentation supports carrier recycling, not a second large ATP yield.
Original carrier-recycling abstraction; the two-ATP count belongs to the stated glycolysis model, not every anaerobic process.
Interpret the supplied visual. What would limit ongoing glycolysis if the needed oxidized carrier were not regenerated?
Answer and explanation

The carrier supply would become insufficient; regeneration enables continued pathway flow under suitable conditions.

NAD⁺ is an electron carrier used in glycolysis, becoming reduced NADH. Fermentation regenerates NAD⁺ by transferring electrons to selected organic products, allowing glycolysis to continue under suitable conditions. In the simple glucose-to-glycolysis account, the net ATP yield is two per glucose; the fermentation conversion is not an additional large ATP-producing electron-transport system. Different fermentation pathways produce different materials, such as lactate or ethanol plus CO₂. “Anaerobic” does not name one identical pathway for every organism.

The carrier supply would become insufficient; regeneration enables continued pathway flow under suitable conditions.

Response criteria

  • Read the structures, axes, directions and units correctly.
  • Connect the evidence with the biological mechanism.
  • Respect stated model assumptions and distinguish an observation from a further inference.

Problem 10

A sample chamber loses 24 oxygen units in 10 min while a matched reference loses 4. Calculate corrected rate and explain why it does not alone provide an exact ATP count.
Answer and explanation

The corrected decline is 20 units, giving 2 units/min. Pathway coupling, oxygen-to-substrate relations and other demands must be specified before converting gas exchange into ATP yield.

The corrected decline is 20 units, giving 2 units/min. Pathway coupling, oxygen-to-substrate relations and other demands must be specified before converting gas exchange into ATP yield.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

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