Question

Choose the correct statement.
A. All proteins have 20 amino acids
B. Both ends of a protein are slimier
C. All proteins are soluble
D. Proteins are formed by peptide bonds

Answer 1

Protein molecules are large, complex molecules formed by one or more twisted and folded strands of amino acids. Proteins are mostly complex molecules that are actively involved in the most basic and important aspects of life. These comprise metabolism, movement, defense, cellular communication, and molecular recognition.

Complete answer: Protein structures are made through condensation of amino acids forming peptide bonds. The amino acid sequence in a protein is known as the primary structure. The secondary structure is set on by the dihedral angles of the peptide bonds, the tertiary structure by the folding of protein chains in space. The association of folded polypeptide molecules to complex functional proteins results in a quaternary structure.
Some characteristics of Peptide bonds are listed below:
-Peptide bonds are strong with partial double bond character.
-They do not fragment by heating or high salt concentration.
-They can be fragmented by exposing them to strong acid or base for a long time at raised temperatures. -Also by some particular enzymes (digestive enzymes).
-Peptide bonds are rigid and planar bonds, so they can stabilize protein structure.
-Peptide bonds contain partial positive charge groups (polar hydrogen atoms of amino groups) and partial negative charge groups (polar oxygen atoms of carboxyl groups).
Hence, the correct answer is Option D.

Note: A peptide bond is formed by a dehydration synthesis or reaction at a molecular level. Peptide bonds are strong with partial double bond nature. Peptide or protein of the amino acid is represented by the three letters or one-letter abbreviation.