A essential amino acid , or an irreplaceable amino acid , is an amino acid that can not be synthesized de novo (from the beginning) by an organism, and so it should be provided in the food. Nine amino acids that can not be synthesized are phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine (ie, F V T W M L I K H).
Six other amino acids are considered important in the human diet, which means their synthesis can be limited under special pathophysiological conditions, such as prematurity in infants or individuals in severe catabolic difficulties. These six are arginine, cysteine, glycine, glutamine, proline, and tyrosine (ie, R C G Q P Y). Five amino acids can be removed in humans, which means they can be synthesized in sufficient quantities in the body. These five are alanine, aspartic acid, asparagin, glutamic acid and serine (ie, A D N E S).
Video Essential amino acid
Human essence
(*) Pyrrolysine, sometimes regarded as "amino acid 22", is not used by humans.
Eukaryotes can synthesize some amino acids from other substrates. As a result, only a portion of the amino acids used in protein synthesis are important nutrients.
Maps Essential amino acid
Suggested daily intake
Estimating daily needs for an irreplaceable amino acid has proved difficult; these numbers have undergone major revisions over the last 20 years. The following table lists WHO and the United States recommend the daily amount currently used for essential amino acids in adult humans, along with their standard one-letter abbreviation.
The recommended daily intake for children aged three years and older is 10% to 20% higher than the adult level and for infants can reach 150% higher in the first year of life. Cysteine ​​(or sulfur-containing amino acids), tyrosine (or aromatic amino acids), and arginine are always needed by growing babies and children.
Relative amino acid composition of protein source
Various attempts have been made to express the "quality" or "value" of different types of proteins. Sizes include biological values, net protein utilization, protein efficiency ratio, protein digestible protein scores and complete protein concepts. These concepts are important in the livestock industry, since the relative deficiency of one or more essential amino acids in livestock feed will have a limiting effect on growth and thus on the feed conversion ratio. Thus, various feed ingredients can be incorporated in combination to enhance the utilization of the net protein, or individual amino acid supplements (methionine, lysine, threonine, or tryptophan) can be added to the feed.
Although plants tend to have less protein per weight than animal sources such as eggs or milk, they remain "complete" in that, overall, they contain all the essential amino acids in human nutrition. The same applies to algae and marine phytoplankton. Eating a variety of plant foods in combination can give the protein a higher biological value. Some of the original food combinations, such as corn and beans, soybeans and rice, or red beans and rice, contain essential amino acids necessary for a sufficient number of humans.
Protein per calorie
It can be shown that common vegetable sources contain adequate protein, often more protein per calorie than the standard reference, raw whole eggs, while other plant sources, especially fruits contain less. For example, while 100 g of raw broccoli provides only 28 cal and 3 g of protein, it has more than 100 mg protein per cal. Eggs contain five times more calories (143 cal) but only four times more protein, about 90 mg protein per cal. However, carrots have only 23 mg protein per cal or twice the minimum recommendation, bananas meet the minimum, and apples are under the recommendation. It is recommended that adult humans obtain 10-35% of their calories as protein, or about 11-39 mg protein per cal per day (22-78 g for 2,000 cal). The US FDA's daily reference value of 50 g protein per 2000 cal is 25 mg/day per day.
Complete protein in non-human animals
Scientists have known since the beginning of the twentieth century that rats can not survive on a diet whose source of protein is simply zein, derived from corn, but recovered if they were given casein from cow's milk. This led William Cumming Rose to discover the discovery of the essential amino acid threonine. Through the manipulation of rodent diets, Rose was able to show that ten essential amino acids for mice: lysine, tryptophan, histidine, phenylalanine, leucine, isoleucine, methionine, valine, and arginine, in addition to threonine. Rose's work then shows that eight amino acids are essential for adult humans, with histidine also important for infants. Long-term studies of histidine are also important for adult humans.
Swap Ability
The difference between essential and non-essential amino acids is somewhat unclear, as some amino acids can be produced from others. Amino acids containing sulfur, methionine and homocysteine, can be converted to one another but can not be synthesized to de novo in humans. Likewise, cysteine ​​can be made from homocysteine ​​but can not be synthesized on its own. Thus, for convenience, sulfur-containing amino acids are sometimes regarded as a collection of the same amino acids such as aromatic amino acids, phenylalanine and tyrosine. Similarly, arginine, ornithine, and citrulline, which can be exchanged by the urea cycle, are considered as a single group.
Effects of deficiency
If one of the essential amino acids is less than that required for the individual, the utilization of other amino acids will be blocked and thus protein synthesis will be less than usual, even with adequate total nitrogen intake.
Lack of protein has been shown to affect all organs and many systems, including brain and brain function of infants and young children; immune system, thus increasing the risk of infection; function of intestinal mucus and permeability, which affect absorption and susceptibility to systemic diseases; and kidney function. Physical signs of protein deficiency include edema, failure to grow in infants and children, poor muscles, dull skin, and thin and brittle hair. Biochemical changes that reflect protein deficiency include low serum albumin and low serum transferrin.
The important amino acids in the human diet are established in a series of experiments led by William Cumming Rose. The experiment involves elemental diets for healthy male graduate students. This diet consists of cornstarch, sucrose, butterfat without protein, corn oil, inorganic salt, known vitamin, large chocolate "candy" made from liver extract flavored with peppermint oil (to supply unknown vitamins), and mixed of highly purified individuals. amino acid. The main outcome measure is the balance of nitrogen. Rose notes that symptoms of anxiety, fatigue, and dizziness are found to a greater or lesser extent whenever human subjects are deprived of essential amino acids.
Deficiency of essential amino acids should be differentiated from protein energy malnutrition, which may manifest as marasmus or kwashiorkor. Kwashiorkor was once associated with a pure protein deficiency in individuals who consume enough calories ("baby sugar syndrome"). However, this theory has been challenged by findings that there is no difference in the diet of children developing marasmus compared with kwashiorkor. However, for example in the USDA Dietary Reference Intakes (DRI), the lack of one or more essential amino acids is described as protein energy malnutrition.
See also
- Biological Value (BV)
- edible protein per unit land area
- Essential fatty acids
- Essential genes
- List of standard amino acids
- Low protein diet
- Orthomolecular medicine
- Protein Digestibility Corrected Amino Acid Score
- Ketogenic amino acids
- Glucogenic amino acids
References
External links
- Amino acid content from some vegetarian foods at veganhealth.org.
- Amino Acid Profile of Some General Means at Virginia Tech.
- Molecular Expressions: The Amino Acid Collection at Florida State University. Displays detailed information and crystal photos of any amino acid.
- vProtein, an online software tool for analyzing the profile of essential amino acids from one and all plant-based foods based on human needs.
Source of the article : Wikipedia
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