We need protein for building muscles. We get calories from protein. Is the protein not burned to produce the calories or does the burning leave the amino acids we need intact?

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We cannot just have carbohydrates to burn for calories. We need protein and fat. Which presumably means we do not just burn them for calories but need some part of them intact.

So do we not burn them for calories? Do we burn part of them for calories and use other parts intact? Does the calorie count include just the part we burn or do we count the other parts we use for calories?

In: Biology

5 Answers

Anonymous 0 Comments

The body can generate some amino acids *de-novo,* generally from certain carbohydrates from the *Citric Acid Cycle* and the *Urea Cycle.*

The citric acid cycle is the process whereby carbohydrates are oxidized to produce ATP, water, and CO2.

Glutamine is generated from Alpha-ketoglutarate and urea. Asparatic acid is generated from Oxaloacetate and certain amine compounds. Arginine is synthesized from fumarate and urea, just as a few examples. Both of these precursors are generated from the citric acid cycle use to oxidize sugars for energy. When proteins are metabolized for energy this process is essen

Humans cannot synthesize eight amino acids. These are called Essential Amino acids and these need to be obtained from food. As nonspecialist omnivores this isn’t usually a problem. In plants the biosynthesis pathways for these 8 are significantly longer and more complex than the others. But plants can get free energy from the sun. Access to nitrogen tends to be a bigger limiting factor for them.

Generally the body tends to retain EAA’s and tends to avoid metabolizing them for energy in favor of the nonessential ones. Although this isn’t a subject that’s well studied. Poor regulation of EAA breakdown may play a role in the pathology of diabetes. This isn’t a problem if you eat a relatively diverse and balanced diet though, unless you have certain rare genetic conditions.

However since children’s bodies are growing they’re more likely to suffer from protein deficiency if they have inadequate food or only have certain specific foods available. Cereal grains, for example, tend to be deficient in 5 or 6 of the 8.

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