Dr Praveen Kumar Agrawal is teaching live on Unacademy Plus
COURSE BIOMOLECULES Lesson Proteins Concept and basic structures Dr. Praveen Kumar Agrawal
PROTEINS Proteins are the main structural components of the body. These are the primary requirement for growth. . Besides forming the structural components, proteins are required for the proper execution of all biological processes in the form of enzymes. Proteins were discovered by J. J. Berzilius. The term 'protein' was coined by G. J. Mulder (1802 1880). (It is de rived from a Greek word - proteios, which means first or primary) Chemically, proteins are the polymers of amino ac ids. Various amino acids are joined together with the help of pep tide bonds to form proteins. Proteins are the most diverse compounds. They occur in many shapes and sizes. . Some are linear and others are variously folded. The size and molecular weights of proteins vary greatly, e.g., the molecular weight of ACTH hormone (a protein, secreted from adrenal cortex) is only 4500. On the other hand, molecular weight of a myosin filament is 4,80,000.
Chemistry of proteins . Proteins are the polymers of amino-acids. Proteins are not freely soluble in water and they usually form colloidal solutions. We have discussed about 20 types of biologically important amino acids. These amino acids are joined together by peptide bonds to form long chains of amino acids. These linear chains are called polypeptide chains. . These represent the simplest kind of proteins. Complex proteins are formed by further processing of these simple proteins Formation of proteins occurs on ribosomes while their processing takes place in endoplasmic reticulum and Golgi complex. The information for the synthesis of a protein is present in DNA (gene). This information comes to the ribosome through mRNA (messenger RNA). Ribosomes in turn assemble the amino acids according to this information in a specific sequence. . Therefore, the sequence of amino acids in a particular protein is very specific and fixed. All kinds of living proteins are synthesised only from 20 types of amino acids, similar to 26 alphabets (English language), which can form millions of words and phrases.
Simple protein Peptide bond NH-H-CO-NH-CH-C0-NH-CH-CO- Peptide bond
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