Matter & Energy in Living Systems — Chapter quiz · Life Science: Biology, Grade 10

Model photosynthesis, respiration, and how atoms cycle while energy is transferred.

Problem 1

What is the main role of ATP in a cell?
  1. It is the energy currency cells spend to power their activities
  2. It stores the cell's genetic instructions
  3. It is the green pigment that captures light
  4. It is the site where photosynthesis occurs
Answer and explanation

It is the energy currency cells spend to power their activities

ATP is the small, usable energy-carrying molecule cells spend to power almost everything they do.

Problem 2

When ATP releases energy, what does it become?
  1. NADPH plus water
  2. ADP plus a free phosphate
  3. DNA plus a sugar
  4. Glucose plus oxygen
Answer and explanation

ADP plus a free phosphate

Breaking off ATP's third phosphate releases energy and leaves ADP (two phosphates) plus a free phosphate.

Problem 3

Which pair are the reactants of photosynthesis?
  1. Oxygen and water
  2. Glucose and carbon dioxide
  3. Carbon dioxide and water
  4. Glucose and oxygen
Answer and explanation

Carbon dioxide and water

Photosynthesis uses carbon dioxide and water (plus light) to make glucose and release oxygen.

Problem 4

In which organelle does photosynthesis take place?
  1. The mitochondrion
  2. The nucleus
  3. The cell membrane
  4. The chloroplast
Answer and explanation

The chloroplast

Photosynthesis occurs in the chloroplast, whose thylakoid membranes hold chlorophyll.

Problem 5

Using 6 CO2 + 6 H2O → C6H12O6 + 6 O2, how many CO2 molecules are needed to make 3 glucose molecules?
Answer and explanation

18 CO2 molecules

Each glucose needs 6 CO2, so 3 × 6 = 18 CO2 molecules.

Problem 6

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

Glucose and oxygen

Respiration breaks down glucose using oxygen: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O.

Problem 7

Where is most of the ATP from aerobic respiration produced?
  1. The nucleus
  2. The electron transport chain on the inner mitochondrial membrane
  3. The cytoplasm during glycolysis
  4. The Krebs cycle in the matrix
Answer and explanation

The electron transport chain on the inner mitochondrial membrane

The electron transport chain makes about 32 ATP — far more than the 2 each from glycolysis and the Krebs cycle.

Problem 8

Using stated 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 this model; biological yields vary.

Problem 9

Which statement best describes the relationship between photosynthesis and cellular respiration?
  1. The products of one process are the reactants of the other
  2. They are identical reactions
  3. Only photosynthesis stores energy; respiration does nothing with energy
  4. Both occur only in the chloroplast
Answer and explanation

The products of one process are the reactants of the other

Photosynthesis's products (glucose and oxygen) are respiration's reactants, and vice versa — they are reverse processes.

Problem 10

In an ecosystem, how do matter and energy move?
  1. Matter cycles and is reused; energy flows one way and is lost as heat
  2. Both matter and energy cycle endlessly
  3. Both matter and energy flow one way and are lost
  4. Matter flows one way; energy cycles
Answer and explanation

Matter cycles and is reused; energy flows one way and is lost as heat

Atoms are reused over and over (matter cycles), but energy enters as sunlight and leaves as heat, so it must be constantly resupplied.

Problem 11

Trace how energy from sunlight ends up in the ATP that powers an animal's muscle cell. Name the two main processes involved.
Answer and explanation

Sunlight is captured by a plant's chloroplasts during photosynthesis and stored as chemical energy in glucose. An animal eats the plant, and its cells break down that glucose through cellular respiration, transferring the energy into ATP. The muscle cell then spends that ATP to contract.

Problem 12

A student claims that plants do not need mitochondria because they have chloroplasts. Explain why this is incorrect.
Answer and explanation

Chloroplasts only store energy by making glucose; they don't release it in a form the cell can spend. Mitochondria carry out cellular respiration to release that stored energy as ATP. Plant cells need ATP constantly — including at night and in non-green parts like roots — so they must have mitochondria and respire, just like animal cells.

Problem 13

At each transfer of energy between organisms, the quantity available to the next organism decreases mainly because
  1. atoms are destroyed
  2. energy is converted to heat and dispersed
  3. ATP cannot be transferred
  4. matter stops cycling
Answer and explanation

energy is converted to heat and dispersed

Every transformation releases some energy as heat, which disperses and is unavailable for cellular work. Atoms are conserved throughout.

Problem 14

Trace the energy in a glucose molecule in your blood back to its original source, naming each transformation.
Answer and explanation

Light energy from the sun was absorbed by chlorophyll in a plant and converted into chemical energy, first in ATP and electron carriers and then in the bonds of sugar built from carbon dioxide and water. The plant or an animal that ate it transferred that sugar through digestion into the bloodstream. In a cell, respiration will release the energy from glucose's bonds and capture part of it in ATP, which couples to cellular work, and the remainder will leave as heat. Each step is a transformation with losses, not a creation of energy.

Response criteria

  • State a biologically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

Problem 15

Independent chapter check: A defined process receives 240 energy units and delivers 72 to the selected useful output. Find efficiency and explain where the remainder belongs in an energy account.
Answer and explanation

Efficiency is 72/240×100 = 30%; 168 units goes to other transfers/storage under the boundary. It is not destroyed, and identifying particular outputs requires a complete measured account.

Efficiency is 72/240×100 = 30%; 168 units goes to other transfers/storage under the boundary. It is not destroyed, and identifying particular outputs requires a complete measured account.

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.

Problem 16

Which statement about the two stages of photosynthesis is accurate?
  1. Both occur in the stroma
  2. The light reactions occur in the thylakoid membranes and carbon fixation in the stroma
  3. Carbon fixation requires light directly
  4. The light reactions produce glucose
Answer and explanation

The light reactions occur in the thylakoid membranes and carbon fixation in the stroma

Light absorption and water splitting happen in the thylakoid membranes; carbon dioxide is fixed into sugar in the stroma using the ATP and NADPH produced.

Problem 17

A grower adds supplementary light to a greenhouse and sees no increase in growth. Propose two explanations and the measurement that would distinguish them.
Answer and explanation

Light may no longer be the limiting factor, with carbon dioxide concentration or temperature now setting the rate; alternatively the plants may already be at their maximum photosynthetic capacity, limited by enzyme quantity. Measuring carbon dioxide concentration and leaf temperature in the greenhouse distinguishes the first possibility, and raising carbon dioxide while holding light constant tests it directly: if the rate rises, carbon dioxide was limiting. If neither more light nor more carbon dioxide raises the rate at an appropriate temperature, the limitation is internal capacity.

Response criteria

  • State a biologically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

Problem 18

Independent chapter check: A lit plant’s gross photosynthetic oxygen production is 14 units/h and its oxygen consumption is 5 units/h under the supplied model. Find net output and explain the oxygen-atom source in oxygenic photosynthesis.
Answer and explanation

Net output is 14−5 = 9 units/h. The released photosynthetic O₂ is traced to water; plants also consume oxygen, and a net gas measurement alone is not gross production.

Net output is 14−5 = 9 units/h. The released photosynthetic O₂ is traced to water; plants also consume oxygen, and a net gas measurement alone is not gross production.

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.

Problem 19

Fermentation allows a cell to
  1. produce as much ATP as aerobic respiration
  2. continue making a small amount of ATP without oxygen
  3. produce oxygen
  4. avoid using glucose
Answer and explanation

continue making a small amount of ATP without oxygen

Fermentation regenerates the carriers glycolysis needs so that a small ATP yield continues without oxygen; it does not approach the aerobic yield.

Problem 20

Explain why cells with high sustained energy demands contain many mitochondria, and why increasing mitochondria would not help a cell deprived of oxygen.
Answer and explanation

The reactions that produce most of a cell's ATP occur in the mitochondria, so a cell with a high sustained demand benefits from having many, and muscle and heart cells accordingly contain large numbers. Those reactions require oxygen as the final electron acceptor, so without oxygen the electron transport chain stops regardless of how many mitochondria are present. A deprived cell is limited to glycolysis and fermentation in the cytoplasm, so additional mitochondria would be idle.

Response criteria

  • State a biologically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

Problem 21

Independent chapter check: 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.

Problem 22

A plant is placed in continuous darkness. Over time its mass decreases because
  1. it stops respiring
  2. it continues respiring while no longer photosynthesizing
  3. it loses chloroplasts
  4. carbon dioxide accumulates in its cells
Answer and explanation

it continues respiring while no longer photosynthesizing

Respiration continues day and night and consumes stored organic matter. Without photosynthesis to replace it, stored mass is depleted.

Problem 23

Explain how carbon atoms cycle between photosynthesis and respiration, and why energy does not cycle with them.
Answer and explanation

Carbon dioxide from the air is fixed into sugar by photosynthesis, that sugar is broken down by respiration in the same plant or in an organism that consumed it, and the carbon returns to the air as carbon dioxide, ready to be fixed again. The atoms are conserved and reused indefinitely. Energy follows a one-way path: it enters as light, part is stored in chemical bonds, and at each transformation some is released as heat that disperses and cannot be recaptured. Matter cycles and energy flows through, which is why sunlight must arrive continuously.

Response criteria

  • State a biologically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

Problem 24

Independent chapter check: For six hours a model produces 10 oxygen units/h and consumes 3. For the remaining 18 hours production is zero and consumption remains 3. Find the day’s net change.
Answer and explanation

Net daytime gain is 6×(10−3)=42 units; later loss is 18×3=54. The day’s net change is −12 units despite positive daytime release under the stated simplified conditions.

Net daytime gain is 6×(10−3)=42 units; later loss is 18×3=54. The day’s net change is −12 units despite positive daytime release under the stated simplified conditions.

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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