Question

The units of proteins which unite in long chain to form proteins, are called as
A. Sugar
B. Purines
C. Pyrimidines
D. Amino acids

Answer 1

Proteins are the most important macromolecules of organisms. The word protein was given by Gerardus Johannes Mulder. Proteins are made up of carbon, hydrogen, oxygen, nitrogen and sulphur. These are highly organized linear polymers of amino acids and called polypeptides.
A protein may be heteropolymer or homopolymer. The protein having a single polypeptide chain is called monomeric protein while the protein having two or more polypeptide chains is termed as oligomeric protein.

Complete answer: To answer this question first we need to know about all the options that we are provided with.
Carbohydrates are also called saccharides or compounds containing sugar. Sugars are simple carbohydrates and are very sweet in taste. They are soluble in water and have low molecular weight.
Nucleotides are the small complex molecules that form a part of the information transfer system in cells. They are the building block of nucleic acids. The nitrogen bases occurring in nucleotides are heterocyclic compounds. Purines are the nine membered molecules with double rings while Pyrimidines are the six membered molecules with single rings.
Amino acids are the small molecules made up of carbon, hydrogen, oxygen and nitrogen. These condense to form peptides in which the carboxylic group of one amino acid joins with the amino group of other amino acids with a loss of water molecule. Successive amino acids may be linked by peptide bonds to form a linear chain of many amino acids.

So, the correct answer is option (D) amino acids because proteins are macromolecules formed from a large number of amino acids.

Note: There are 20 amino acids that are normal components of protein and are called protein amino acids. Proteins are the antibodies that help to bind with foreign particles to protect our body. Proteins are also called transport or storage proteins because they carry atoms and molecules within cells and throughout the body.