How much ATP one glucose molecule earns, and why the figure in a book is never exact. How fats and proteins enter the pathway and how the pathway builds new molecules. The respiratory quotient and what it tells about the substrate.
3 lessons, about 1 h 15 min3 simulations10 problems3 practice questionsPython in every lesson
Created by StemPy LabOne glucose can be followed through glycolysis, the link reaction, the Krebs cycle and the electron transport system. NCERT counts 36 ATP in all, from 4 made directly, 28 from NADH and 4 from FADH2. This is a theoretical figure, because a living cell uses all its pathways together, and other books give 38 or about 30.
Glucose is the favourite substrate, but fats and proteins can be respired. Glycerol enters as PGAL, fatty acids as acetyl CoA, and amino acids as pyruvic acid, acetyl CoA or a Krebs cycle intermediate. The same pathway is also used to build fats and proteins, so it is amphibolic and not only catabolic.
The respiratory quotient is the volume of carbon dioxide released divided by the volume of oxygen taken in. It is 1 for carbohydrates, about 0.9 for proteins, 0.7 for fats and more than 1 for organic acids. It tells what substrate a tissue is respiring.
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