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Protein

Very important, both from the point of view of Food Science and Nutrition. The word “protein” is derived from the Greek language meaning “holding first place”.

No life would exist without it. It is needed for all living cells both plant an d animal.

Structure of Protein

·         Organic compounds, containing carbon, hydrogen, oxygen and nitrogen.

·         No other nutrient apart from protein supplies the body with nitrogen, some proteins also contain sulphur and phosphorus.

·         There is a large range of proteins e.g. gluten and keratin, but they are all built from the same 20 building blocks, called amino acids.

·         What makes one protein unique from the other is the number , sequence and types of amino acid in protein.

Amino Acids

Have the same basic structure. They have at least one amino group (NH2) and at least one carboxyl group (COOH). The amino and carboxyl groups are attached to a central carbon atom.

Basic Structure of Amino Acid

The building blocks of protein are amino acids. Amino acids are compounds containing, carbon, hydrogen, oxygen and nitrogen and in some cases sulphur.

Acid Group

Amino Group

 

 

 

 

 

 

 

Classifying Amino Acids

Indispensable

Out of the 20 amino acids 8 are considered indispensable for all people and one must be supplied in the diets of rapidly growing infants (the body cannot manufacture these and they must therefore be present in food).

Dispensable

Amino acids which the body is able to make for itself by a process called Transamination, takes place in the liver under the influence of an enzyme. HN2 (amino) group from an amino acid of which there is an excess is transferred to another molecule and a new amino acid is created.

The only known foods to provide nearly the correct mixture of amino acids for human growth are eggs and human breast milk.

 

The building of a protein molecule from Amino Acids.

 

AA1

AA3

AA4

AA2

Peptide Link

Plus                             3 water molecules

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

After Reaction:

A small portion of a protein molecule is built up from amino acid.

·         Protein molecules are built from amino acids which have chemically combined. A single protein, molecule of average size will have around 500 amino acids.

·         Every time that 2 amino acids join up, a molecule of water is eliminated.

·         Protein chains are formed when the amino group (NH2) of one amino acid reacts with the acidic [COOH] group of the next one. The join is called a peptide link.

·         Protein building does not end here; this is the first step on the path to working out total protein structure and is referred to as Primary Protein Structure. The chains of amino acids do not necessarily remain in straight lines. It is the secondary protein structure that, it gives the molecule its…