Give information on the structural organization of proteins. Mention their general functions.

(N/A) $\rightarrow$ Proteins are polypeptides. They are linear chains of amino acids linked by peptide bonds.
$\rightarrow$ Each protein is a polymer of amino acids. There are $21$ types of amino acids (e.g.,alanine,cysteine,proline,tryptophan,lysine,etc.).
$\rightarrow$ Protein is a heteropolymer. $A$ homopolymer has only one type of monomer repeating '$n$' number of times.
$\rightarrow$ Certain amino acids are essential for our health and they have to be supplied through our diet. Dietary proteins are the source of essential amino acids.
$\rightarrow$ Amino acids can be essential or non-essential. Essential amino acids are obtained through our food,while non-essential amino acids are those which our body can synthesize.
$\rightarrow$ Proteins carry out many functions in living organisms: some transport nutrients across cell membranes,some fight infectious organisms,some act as hormones,and some function as enzymes.
$\rightarrow$ Some proteins and their functions:

Protein	Functions
Collagen	Intercellular ground substance
Trypsin	Enzyme
Insulin	Hormone
Antibody	Fights infectious agents
Receptor	Sensory reception (smell,taste)
$GLUT$-$4$	Enables glucose transport in the cells

$\rightarrow$ Collagen is the most abundant protein in the animal world,and Ribulose bisphosphate Carboxylase Oxygenase (RuBisCo) is the most abundant protein in the whole of the biosphere.