Metabolism – following atoms through digestion, respiration and building
BiologyCell BiologyAges 15–16
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Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Cell Biology
Follow the atoms of a meal: starch, protein or fat is hydrolysed into monomers, some of the monomers are respired with oxygen to carbon dioxide and water, making ATP, and that ATP powers the condensation reactions that build glycogen, body protein or body fat. A table counts the C, H, O and N atoms and the mass taken in and given out, which always balance. A second screen builds glycogen, a protein chain and a fatty acid one unit at a time and adds up the ATP and NADPH from catabolism that each one costs.
Lesson: Metabolism: catabolism and anabolism (digestion, respiration and biosynthesis)
What it shows
Metabolism is the sum of the reactions in a body. Catabolic reactions break molecules down: digestion hydrolyses food polymers into monomers, and respiration oxidises some of them to carbon dioxide and water, releasing energy that is stored in ATP. Anabolic reactions build molecules up: condensation joins monomers into glycogen, proteins and fats, and every new bond costs ATP; fatty acid synthesis also needs NADPH. The model uses a chain of alanine as the protein and tripalmitin as the fat, net equations and textbook ATP values. No atom is created or destroyed, so the atom counts and the mass always balance.
How to use
On Atom map, choose a Food and the number of Food units, set Units respired and press Run. Use Follow atoms of to pick Carbon, Hydrogen, Oxygen or Nitrogen and see where those atoms end up, then compare the totals in the table. Respire too little and some monomers stay unused. On Building (anabolism), pick a Product, set Units to add and press Step to watch the ATP and NADPH being spent.
Parameters you can change
- Screen Atom map: food to body, Building (anabolism)
- Food Starch, Protein (alanine model), Fat (tripalmitin)
- Food units 4–24
- Units respired 0–24
- Follow atoms of Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N)
- Product on the Building screen Glycogen, Protein, Fatty acid
- Units to add on the Building screen 1–7
Questions to explore
- Why are there more hydrogen and oxygen atoms in the monomers than in the food they came from?
- Why must part of the food be respired before the rest can be built into body molecules?
- Which building process needs NADPH as well as ATP, and what is the NADPH used for?
