Matter & Energy in Living Systems — Chapter Practice, Grade 10

the cell's main energy currency

ATP is the small, spendable energy-carrying molecule cells use to power almost every activity — its nickname is the cell's energy currency.

ATP has three phosphate groups and ADP has two

ATP has three phosphate groups; ADP has two. Hydrolysis forms ADP and inorganic phosphate.

36.5 kcal

5 × 7.3 = 36.5 kcal under the stated conditions; actual cellular values depend on conditions.

When ATP releases energy it becomes ADP plus a phosphate, but it isn't discarded — the cell adds energy from food or sunlight to reattach the phosphate and turn ADP back into ATP. This ATP–ADP cycle repeats over and over, like recharging a battery.

An oak tree

An oak tree makes its own food from sunlight, carbon dioxide, and water, so it is an autotroph (producer). The wolf, mushroom, and human are heterotrophs that must eat other organisms.

Continuous regeneration keeps production matched to ongoing demand.

Cell work continually converts ATP to ADP and phosphate.

Available ATP is limited, so metabolic processes must replenish it.

Response criteria

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

Account for both hydrolysis and regeneration.

Energy-coupled transport cannot continue normally without sufficient chemical energy supply.

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

No. ATP is repeatedly regenerated and used, so turnover and standing amount differ.

The pathway, reaction conditions, coupling and other energy transfers matter; ATP count is only one defined output.

ATP hydrolysis can support an energetically linked change, such as a transport protein’s conformational cycle. The useful change depends on the overall reaction and coupling, not on energy being released by breaking one isolated bond. ADP and inorganic phosphate can be used to rebuild ATP through other energy-transferring processes. ATP therefore serves repeated short-term transfers rather than a perpetual source. Count a stated ATP demand separately from the food input or the rate of ATP production; molecule count and energy amount are different quantities.

The pathway, reaction conditions, coupling and other energy transfers matter; ATP count is only one defined output.

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.

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.

Carbon dioxide and water

Photosynthesis uses carbon dioxide and water (plus light energy) to build glucose and release oxygen. Glucose and oxygen are the products, not the reactants.

The chloroplast

Photosynthesis happens in the chloroplast, whose thylakoid membranes hold the chlorophyll that captures light.

6 O2 molecules

The equation 6 CO2 + 6 H2O → C6H12O6 + 6 O2 shows 6 molecules of O2 released per glucose.

The oxygen comes from splitting water (H2O). This happens in the light-dependent reactions, in the thylakoid membranes, where light energy is used to break water apart.

absorbs red and blue light and reflects green light

Chlorophyll absorbs mostly red and blue wavelengths to power photosynthesis and reflects green light back to our eyes, which is why plants look green.

CO₂ supplies carbon; water supplies the oxygen atoms released as O₂.

Carbon is incorporated from CO₂.

In oxygenic photosynthesis, released O₂ comes from water.

Response criteria

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

Light supplies energy; it is not a source of carbon atoms.

Water supplies electrons and hydrogen in light reactions; released O₂ originates from water.

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

Yes. Cellular respiration can continue while photosynthesis occurs.

They measure different quantities; relating them requires controlled biological and optical conditions.

A pigment interacts with light at particular wavelengths. An absorption spectrum shows absorption versus wavelength, while an action spectrum shows a measured biological process versus wavelength under controlled conditions. Pigments and associated structures can broaden useful light capture, but absorbed light is not all converted into organic production. Leaf thickness, other pigments, light intensity and physiological conditions influence the outcome. A leaf’s visible color reflects light reaching the observer, not proof that the other wavelengths never interact.

They measure different quantities; relating them requires controlled biological and optical 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.

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.

Glucose and oxygen

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

electron transport chain on the inner mitochondrial membrane

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

2 ATP

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

15 times

30 ÷ 2 = 15 under the stated model.

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.

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.

Atoms and energy must be accounted for separately.

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

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

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

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.

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.

The products of one are the reactants of the other

Their simplified net equations connect reactants and products, but their biochemical pathways differ.

cycles; flows one way

The same atoms are reused over and over (matter cycles), but energy enters as sunlight and is lost as heat at each step (energy flows one way and must be resupplied).

Carbon atoms can be reused; energy is transferred and dispersed as heat. Biological work needs usable input, and matter also crosses real forest boundaries.

Both plants and animals commonly carry out aerobic respiration

Plants and animals commonly use aerobic respiration; some specialized cells and other organisms use different pathways.

24 CO2 molecules

Each glucose respired releases 6 CO2, so 4 × 6 = 24 CO2 molecules.

Respiration continues even when light-dependent photosynthesis stops.

Cells still need ATP for maintenance and work.

Aerobic respiration can continue using stored organic molecules when photosynthesis is not occurring.

Response criteria

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

Measure net flux rather than treating it as one process.

12−5=7 units, under the stated boundary.

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

Matter can cycle, but energy inputs and thermal losses require ongoing external energy.

No. Equal production and consumption can balance to zero while both continue.

Gross production refers to production before a specified subtraction; net exchange is the signed balance of inflows/outflows or production/consumption at the stated boundary. In this oxygen model, production is 12 units/h and consumption four, so net release is eight. A zero net rate can therefore coexist with active production and consumption. Definitions must identify the variable: ecosystem net carbon production, leaf oxygen exchange and biomass growth are related but different accounts. Changing a light level may alter more than one process.

No. Equal production and consumption can balance to zero while both continue.

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.

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.