Question

In: Biology

What is an amino acid? How many amino acids are there? 

What is an amino acid? How many amino acids are there? 

Solutions

Expert Solution

Aminoacids are organic, structural monomer units and are building blocks of proteins through peptide bonds.

There are 20 standard and naturally occurring aminoacids.

(in nature, total 22, in Eukaryotes and humans 21 aminoacids)

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Aminoacids are organic nutrients that appear in foods and in the human body either as building blocks of proteins or as free amino acids.

Amino acids are made of the amino group (NH2), carboxyl group (COOH) and a side chain containing carbon, hydrogen or oxygen; two amino acids (cysteine and methionine) also contain sulfur and one (selenocysteine) contains selenium.

It is the R-group or side chain that differs between the 20 amino acids.

Amino acids are the structural units (monomers) that make up proteins. They join together to form short polymer chains called peptides or longer chains called either polypeptides or proteins. These polymers are linear and unbranched, with each amino acid within the chain attached to two neighboring amino acids.

Amino–Acid–Name–with (Abbreviation)

Classification

1. Histidine (His)
2. Isoleucine (Ile)
3. Leucine (Leu)
4. Lysine (Lys)
5. Methionine (Met)
6. Phenylalanine (Phe)
7. Threonine (Thr)
8. Tryptophan (Trp)
9. Valine (Val)

ESSENTIAL Amino Acids

The 9 amino acids on the right are essential (vital), which means they are necessary for the human life and health but cannot be produced in your body so you need to get them from foods.

10. Arginine (Arg)
11. Cysteine (Cys)
12. Glutamine (Gln)
13. Glycine (Gly)
14. Proline (Pro)
15. Serine (Ser)
16. Tyrosine (Tyr)

CONDITIONALLY ESSENTIAL Amino Acids

These amino acids can be synthesized in your body, but in certain circumstances, like young age, illness or hard exercise, you need to get them in additional amounts from foods to meet the body requirements for them. Ornithine is also considered conditionally essential amino acid, but it does not form proteins .

17. Alanine (Ala)
18. Asparagine (Asn)
19. Aspartic acid (Asp)
20. Glutamic acid (Glu)

21. Selenocysteine

NONESSENTIAL Amino Acids

These amino acids can be synthesized in your body from other amino acids, glucose and fatty acids, so you do not need to get them from foods.

Twenty-two amino acids are naturally incorporated into polypeptides and are called proteinogenic or natural amino acids. Of these, 20 are encoded by the universal genetic code. The remaining 2, selenocysteine and pyrrolysine, are incorporated into proteins by unique synthetic mechanisms.
In eukaryotes, including humans, there are only 21proteinogenic amino acids, the 20 of the standard genetic code, plus selenocysteine.


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