63. Metabolism of the Nutrients in the organism. Metabolism of Carbohydrates: the level and regulation of Glucose in the circulating blood. Metabolism of Proteins and its control. Me-tabolism of Lipids and its control.

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.