Student Sheet: EVALUATE: Tracing Matter and Energy
Cut out each step. Glue the 12 steps in order to show the set of events that explain how a labeled
carbon atom in a molecule of atmospheric carbon dioxide ends up in a human muscle protein.
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Some amino acids may become involved in aerobic respiration, releasing energy. (breakdown)
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Energy from cellular respiration can be linked to the biosynthesis of protein, during which
anabolic reactions incorporate labeled amino acids into protein. This labeled protein may be
incorporated into muscle tissue in the cow. (synthesis)
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A cow eats the plant, which contains labeled macromolecules. (breakdown)
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Solar energy is trapped in chemical form through photosynthesis.
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The labeled carbon is fixed into sugars through reactions that use some of the energy trapped by
photosynthesis. (breakdown of the carbon dioxide molecule; synthesis of a sugar molecule)
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Human digestion breaks down this labeled protein to its component amino acids, one of which
contains the labeled carbon atom. (breakdown)
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The plant uses these labeled sugars to synthesize labeled macromolecules, including labeled
starch and labeled proteins. (synthesis)
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Labeled carbon dioxide from the air is taken up by a plant leaf through the stomates.
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In the cow, the labeled plant macromolecules are broken down to labeled amino acids and
labeled sugars through digestive processes. (breakdown)
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In biosynthetic reactions in the human, which require energy, the labeled amino acid becomes
incorporated into muscle protein as the body rebuilds tissue after exercise; thus, the labeled
carbon from carbon dioxide becomes incorporated into protein in a human muscle. (synthesis)
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The cow is slaughtered and processed, and then a human eats a hamburger that includes the
labeled protein. (breakdown)
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The labeled sugars then are broken down further by the process of cellular respiration, which
releases energy in the metabolically useful form of ATP. (breakdown)