Proteins are unbranched polymers constructed from 22 standard α-amino acids.
The protein show four levels of structural organisation; the primary structure, secondary structure, tertiary structure and quaternary structure.
The structure of proteins are stabilized by peptide bonds between the amino acid and hydrogen bond between the peptide chainds.
The primary structure of a protein is determined by the sequence of amino acids, but secondary and tertiary structures of protein define their natural or native conformation.
The solubility of protein varies according to the pH, ionic strength, nature of solvent, temperature etc.
Proteins can be classified as simple proteins or conjugated proteins on the basis of their composition.
The proteins can also be classified as fibrous proteins or globular proteins on the basis of their shape.
Proteins play a major part in body structure and function as most of the molecules like antibodies, immunoglobulins, hemoglobin, myoglobin ,most of the enzymes are proteins.
So proteins are also called building blocks of the body.
Blood and lymph are the two circulating fluids in the animal body. Blood belongs to the circulation system whereas lymph belongs to the lymphatic system. Blood contains pigments which carry oxygen. Therefore, blood can be found in different colors in different types of organisms. But, lymph is a colorless fluid. Blood is composed of red blood cells, white blood cells, platelets and a fluid called plasma. Lymph is composed of white blood cells and a watery fluid. Both blood and lymph possess a circulatory function as well as an immune function. The main difference between blood and plasma is that blood circulates inside blood vessels whereas lymph circulates inside lymphatic vessels.
A scientific theory explains the reason for the occurrence of phenomena. However, a scientific law is limited to applicability and does not give any explanation regarding the phenomena in which it can be applied to.
