According to my book Concise Biology Revised edition of Selina Publication for Class IX, "1 mole of glucose releases 686 kilocalories of energy". It's also mentioned there that " They produce more energy than carbohydrates do - one mole of fat releases 9.45 kcal of energy". I think that the measure of the amount of released energy has been messed up. Some sites say that "1 gram of fat releases 9.45 kcal of energy." But, I would highly appreciate it if anyone could explain it in a detailed manner (probably through mathematical calculations) and help me to know the correct value along with unit.
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2$\begingroup$ Check that you have your units correct. $\endgroup$– Bryan Krause ♦Commented Jul 14 at 18:50
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$\begingroup$ Yes, that's what written in my book. $\endgroup$– KakiaririkiCommented Jul 15 at 5:22
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2$\begingroup$ Welcome to SE Biology. Please read the Help on asking good questions. There are two points I would make. 1. You should give full details of your book, and verbatim quotations of the sentences containing the points at issue. We need to be sure you are not misinterpreting what is written, and may even be able to check the context. I personally would be suspicious of a book that talked about compounds “releasing energy”, or referring to “fat” rather than a specific triglyceride, for example. 2. We expect posters to try to answer their own questions. Have you done an Internet search on this? $\endgroup$– DavidCommented Jul 15 at 8:25
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$\begingroup$ I have edited my question...is it okay now? $\endgroup$– KakiaririkiCommented Jul 15 at 15:48
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1 Answer
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A triglyceride can produce 450 ATP compared to glucose's 32. Triglycerides win in energy production.
TL;DR One pyruvate molecule ultimately produces 15 ATP. Glucose produces 32 pyruvate for a total of 15 X2 ATP + 2 ATP = 30 +2 =32 ATP per molecule of glucose including the 2 ATP generated by anaerobic respiration.
Triglycerides are a glycerol molecule linking 3 fatty acids. Each fatty acid has 16, 18, or 20 carbons in its composition, which is convenient, because pyruvate is a 2 carbon molecule. fatty acids can produce 8, 9, or 10 pyruvate molecules. So fatty acids can produce 15x 8 ATP = 120 ATP. A glyceride, having 1,2,or 3 Fatty acids can produce up to 30 pyruvate molecules. 15 X30 ATP = 450 ATP One triglyceride> 450 ATP One glucose molecule> 32 ATP
Fatty acids have the potential to produce more ATP than glucose could hope to produce.
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$\begingroup$ To answer the first question a little better: glucose gives quick energy. It is broken down to create 2 ATP for a muscle, say, or the brain, for example. $\endgroup$ Commented Aug 7 at 15:06