Amino Acid
Definition
The monomer unit of proteins. All 20 standard amino acids share a central carbon bonded to an amino group, a carboxyl group, a hydrogen, and a variable side chain (R-group) that determines the amino acid's chemical properties. Peptide bonds link amino acids end-to-end to form polypeptide chains.
- Role
- Monomer unit of proteins
- Standard count
- 20 standard amino acids
- Shared structure
- Central carbon with amino, carboxyl, R-group
- Linkage
- Peptide bond
Common questions
How does the R-group determine an amino acid's role in a protein?+
The variable side chain gives each amino acid distinct chemical properties, such as being acidic, basic, polar, or hydrophobic, and the sequence of these side chains along a chain determines how the resulting protein folds and what it can bind or catalyze.
Why are amino acids relevant to forensic biological evidence beyond DNA?+
Proteins and enzymes built from amino acids, such as blood group substances and body-fluid-specific enzymes, provide an older but still useful layer of identification and body-fluid typing that is independent of nuclear DNA profiling.
Related terms
- Haemoglobin
- The iron-containing oxygen-transport protein in red blood cells, composed of four polypeptide subunits each with a haem prosthetic group. Its pseudoperoxidase activity...
- Isoenzyme (Isozyme)
- Multiple molecular forms of the same enzyme that differ in amino acid sequence but catalyse the same reaction. In forensic serology, isoenzyme...
- Peroxidase
- An enzyme that catalyses the transfer of oxygen from hydrogen peroxide to an electron donor, often producing a coloured product. Haemoglobin has...
- Protein Denaturation
- The loss of a protein's three-dimensional structure without breaking peptide bonds, caused by heat, pH change, UV radiation, or chemical agents such...
- Proteolysis
- The hydrolytic cleavage of peptide bonds by proteolytic enzymes (proteases). In biological evidence, proteolysis occurs via endogenous cellular proteases released during autolysis...