Tuesday, June 15, 2010

Nutrition Series: The Basics - Amino Acids, Proteins, and Enzymes

(pictured is a space-filling model of myoglobin, a protein found in muscle tissue)


Amino acids are the building blocks of proteins. They connect to each other in long chains to form proteins, which take the form of very complex shapes, with many bends and folds.
There are 22 amino acids that comprise the proteins in our cells.
These can be subdivided into
Essential/non-essential - there are 8 amino acids considered essential, in that they can not be produced by our bodies and must be obtained through the diet. However, certain essential amino acids can be synthesized from certain non-essential ones. Also, in certain populations, non-essential amino acids become essential because of some type of disease or disorder; these amino acids are considered conditionally essential.
Essential Amino Acids: Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and Valine
Non-essential: Alanine, Aspartate(aka aspartic acid), Glutamate(aka glutamic acid), Pyrrolysine*, Selenocysteine* (*unclassified)
Conditionally Essential: Histidine, Tyrosine, Arginine, Cysteine, Glutamine, Glycine, Proline, Serine, and Asparagine.
Amino acids can also be characterized as either glucogenic, ketogenic or both. Glucogenic describes those amino acids that can be converted to glucose through gluconeogenesis. Ketogenic amino acids are those that can produce ketones through the process of ketogenesis
Glucogenic Amino Acids: Glycine, Serine, Valine, Histidine, Arginine, Cysteine, Proline, Alanine, Glutamate, Glutamine, Aspartate, Asparagine, and Methionine.
Both glucogenic or ketogenic: Isoleucine, Threonine, Phenylalanine, Tyrosine, and Tryptophan.
Ketogenic Amino Acids: Leucine and Lysine.
Enzymes are proteins that catalyze(or increase the rate of) chemical reactions. Most enzyme reaction rates are millions of times faster than comparable un-catalyzed rates.

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