BIOC 303 Lecture Notes - Lecture 2: Nitrogen Balance, Polyamine, Cachexia
Document Summary
Assessing the importance of amino acid and protein metabolism. The quantitative importance of proteins and amino acids is becomes clear when we consider the overall contribution to body mass and various measures of the dynamics of supply and utilization. Water represents approximately 65% of our body weight, so the dry mass for a 70kg individual is about 25kg. The amount of fat stored varies enormously between individuals. Those with a lean phenotype are generally considered to have fat stores that make up 10-14% of body weight. For a 70kg individual, this would approach ~10kg of fat mostly as membrane lipids and triglycerides. Of the remaining dry mass, protein contributes about 10kg. 500gm), minerals and nucleic acids make up the final ~5kg. Healthy adult humans maintain a relatively constant body mass over many years provided caloric balance is maintained. Nitrogen balance is maintained when daily dietary intake of nitrogen is equal to the amount of nitrogen excreted.
