Proteins
Proteins play a major role in ensuring your health , have innumerable functions in the
body include :
1. Proteins serve as a major energy supplier.
2. Building and repairing of body tissues
3. Regulation of body processes and formation of enzymes and hormones.
4. Formation of antibodies that enable the body to fight infection .
5. Proteins form a major part of your body, next to water, the composition of
proteins in the body is like that muscle contains about 1/3 protein, bone about
1/5 part and skin consists of 1/10 portion. The rest part of proteins is in the
other body tissues and fluids.
Amino acids are the basic building blocks of proteins. Fundamentally, amino acids
are joined together by peptide bonds to form the basic structure of proteins.
Amino acids are carbon compounds that contain two functional groups: an amino
group (NH2) and a carboxylic acid group (COOH).
Examples of amino acids structures
Biuret's test
This test is a general test for proteins
The Biuret's test is a chemical test used for detecting the presence of peptide bonds,
In the presence of peptides, a copper(II) ion forms a violet-colored complex in an
alkaline solution. The Biuret's reaction can be used to assay the concentration of
proteins because peptide bonds occur with the same frequency per amino acid in the
peptide.
Steps:
1.
Put 1 ml of protein solution in a clean test tube.
2.
Add 6 drops of biuret reagent.
3.
Observe formation of violet color indicates presence of protein.
Test
Observation
Result
Biuret's test
Violet colored complex
Protein
Essential
Nonessential
Isoleucine
Alanine
Leucine
Asparagine
Lysine
Aspartic Acid
Methionine
Cysteine*
Phenylalanine
Glutamic Acid
Threonine
Glutamine*
Tryptophan
Glycine*
Valine
Proline*
Essential amino acids must be obtained from the
Selenocysteine*
diet , and cannot be made by the body
Serine*
Tyrosine*
Arginine*
Histidine*
Ornithine*
Taurine*
Non essential amino acids because they made by the body, not need be obtained from the diet