Four changes happen in cells. (i) Amino acids are joined into a protein…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Four changes happen in cells. (i) Amino acids are joined into a protein. (ii) Glucose is broken down to lactic acid in a muscle. (iii) Sugar is built into starch in a potato. (iv) A fat is broken down to release energy. (a) Say whether each change is anabolic or catabolic. (b) In which of them does the cell capture energy as ATP, and in which does it spend ATP? (c) Why is ATP called the energy currency?
Need a reminder? The key ideaShow
Metabolism is all the chemical reactions of a living thing, in pathways of enzyme-catalysed steps. Anabolic pathways build molecules and use energy; catabolic pathways break them down and release energy, which is stored in ATP, the energy currency. Metabolic flux is the rate of flow through a pathway. A closed system reaches equilibrium: no net flow, no free energy and no work. A living cell is an open system held in a steady state far from equilibrium by a continuous flow of matter and energy.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Naming each one. (i) and (iii) build larger molecules, so they are anabolic. (ii) and (iv) break molecules down, so they are catabolic.
Step 2. ATP. The catabolic changes, (ii) and (iv), release energy, which the cell captures as ATP. The anabolic changes, (i) and (iii), spend ATP.
Step 3. The currency. ATP is made where energy is released and spent where energy is needed, and it is rebuilt again and again, like money.
Answer: (a) anabolic, catabolic, anabolic, catabolic; (b) ATP is made in (ii) and (iv) and spent in (i) and (iii); (c) it carries energy from where it is released to where it is used.
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