Question

Each polypeptide in a protein has amino acids linked with each other in a specific sequence. This sequence of amino acids is said to be:
A. Primary structure of proteins
B. Secondary structure of proteins
C. Tertiary structure of proteins
D. Quaternary structure of proteins

Answer 1

Polypeptides are long chains of amino acids linked with peptide bonds and these long chains are called proteins. Different structures of proteins have different functionalities like sequence of amino acids, local sub structures and three dimensional structures.

Complete step by step answer:
Before getting into the sequence of amino acids we need to know about polypeptides. Peptides are short chains of amino acids linked with peptide bonds which are between two to fifty amino acids. Chains which are fewer than ten or fifteen amino acids are called oligopeptides and also include dipeptides, tripeptides and tetrapeptides.

A polypeptide is a longer continuous and unbranched peptide chain of up to approximately fifty amino acids. Polypeptides that contain more than approximately fifty amino acids are known as proteins. Proteins consist of one or more polypeptides arranged in a biologically functional way often bound to ligands such as coenzymes and cofactors or to other proteins.

Amino acids that have been incorporated into peptides are termed as residues. And a water molecule is released during formation of each amide bond. All peptides except cyclic peptides have an N-terminal or amine group and C-terminal or carboxyl group residue at the end of the peptide.
Now as we have learned about polypeptides we also need to know the difference between primary, secondary, tertiary and quaternary structure of Proteins.
A. Primary structure of proteins refers to the sequence of amino acids in the polypeptide chain.
The primary structure is held together by peptide bonds that are made during the process of protein biosynthesis.
B. Secondary structure of proteins refers to highly regular local sub structures on the actual polypeptide backbone chain. These structures are defined by patterns of hydrogen bonds between the main chain peptide groups.
C. Tertiary structures refers to the three dimensional structure of monomeric and multimeric protein molecules which are folded into a compact globular structure.
D. Quaternary structure is the three dimensional structure consisting of aggregation of two or more individual polypeptide bonds that operate as a single functional unit.
Now from the above information about different structures of proteins we get to know that sequences of amino acids are referred to by the primary structure of amino acids.

**Therefore the answer is option A.

Note: **
Polypeptides are long chains of amino acids linked with peptide bonds and these long chains are called proteins. Primary structure of proteins refer to sequence of amino acids, secondary refer to local sub structures and tertiary and quaternary look into the three dimensional structure of proteins.