Covers protein metabolism, from essential and non-essential amino acids through digestion, deamination and urea formation to nitrogen balance, then hormonal and neural control of protein turnover. Lipid digestion and absorption follow, including bile acids, chylomicrons and lymphatic transport, then lipid utilisation for energy, and finally hormonal regulation of lipid metabolism. Closes with recap questions on these points.
Topic 54 of 104 in the MU Sofia syllabus for Physiology (Medicine, Year 2). The free AceMed note covers it in 6 sections, about 538 words (4 min of reading), with 15 flashcards.
In this note
Protein and lipid metabolism. Regulation.
Protein Metabolism
Regulation of Protein Metabolism.
Lipid Metabolism
Regulation of Lipid Metabolism
Recap Questions.
Protein Metabolism
Amino Acids: The human body requires 20 amino acids.
11 can be synthesized internally (non-essential amino acids).
9 must be obtained through diet (essential amino acids).
Protein Digestion and Absorption:
Initial breakdown into smaller peptide chains occurs in the digestive system via enzymes: pepsin, trypsin, chymotrypsin, and elastase.
Further breakdown into individual amino acids is facilitated by carboxypeptidase, aminopeptidase, and dipeptidase, enabling absorption into the bloodstream.
Next is the breakdown of amino acids into their constituent parts (catabolism). This removes the nitrogen or amino group from the amino acids. The process is called deamination. Deamination breaks the amino group down into ammonia and keto acid carbon skeleton. Ammonia (is toxic) is converted to urea, filtered through the kidneys, and excreted in urine (urea is the primary storage of nitrogen)
Nitrogen Balance: Protein serves as the primary source of nitrogen in the body.
For every 6.25 grams of protein consumed, 1 gram of nitrogen is excreted.
Nitrogen balance can be assessed to determine protein absorption by multiplying the grams of nitrogen excreted by 6.25.
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