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Lysine (symbol Lys or K) [2] is an α-amino acid that is a precursor to many proteins.Lysine contains an α-amino group (which is in the protonated −NH + 3 form when the lysine is dissolved in water at physiological pH), an α-carboxylic acid group (which is in the deprotonated −COO − form when the lysine is dissolved in water at physiological pH), and a side chain (CH 2) 4 NH 2 (which ...
Liebig's law has been extended to biological populations (and is commonly used in ecosystem modelling).For example, the growth of an organism such as a plant may be dependent on a number of different factors, such as sunlight or mineral nutrients (e.g., nitrate or phosphate).
The limiting amino acid is the essential amino acid which is furthest from meeting nutritional requirements. [4] This concept is important when determining the selection, number, and amount of foods to consume because even when total protein and all other essential amino acids are satisfied if the limiting amino acid is not satisfied then the ...
A rare exception to the dominance of α-amino acids in biology is the β-amino acid beta alanine (3-aminopropanoic acid), which is used in plants and microorganisms in the synthesis of pantothenic acid (vitamin B 5), a component of coenzyme A. [77]
The carbon skeletons of many non-essential amino acids are made from citric acid cycle intermediates. To turn them into amino acids the alpha keto-acids formed from the citric acid cycle intermediates have to acquire their amino groups from glutamate in a transamination reaction, in which pyridoxal phosphate is a cofactor.
Within a sequence, amino acids that are important for folding, structural stability, or that form a binding site may be more highly conserved. [17] [18] The nucleic acid sequence of a protein coding gene may also be conserved by other selective pressures. The codon usage bias in some organisms may restrict the types of synonymous mutations in a ...
Protein quality is the digestibility and quantity of essential amino acids for providing the proteins in correct ratios for human consumption. There are various methods that rank the quality of different types of protein, some of which are outdated and no longer in use, or not considered as useful as they once were thought to be.
Amino acid composition is the principal effect. All proteins are made up of combinations of the 21 biological amino acids. Some of these can be synthesised or converted in the body, whereas others cannot and must be ingested in the diet. These are known as essential amino acids (EAAs), of which there are 9 in humans.