Cytology and Genetics( March 14) - NEET MCQ

The given molecule is adenylic acid. It is a nucleotide found in RNA. It is an ester of phosphoric acid with the nucleoside adenosine. It consists of a phosphate group, a pentose sugar ribose, and the nucleobase adenine.

Double helix model of DNA was proposed by James Watson and Francis Crick in 1953 based on X-ray diffraction data produced by Maurice Wilkins and Rosalind Franklin.

The number of substrate molecules changed per minute by a molecule of enzyme is called turn over number. Higher the turn over number more effective is the enzyme.

The diagram shown is a uracil which is a pyramidine belonging to nitrogen bases.

• There are 20 naturally occurring amino acids.
• All the amino acids except glycine are chiral. Amino acids are classified as acidic, basic or neutral based on the relative number of amino and carboxylic groups.
• Amino acids are classified as essential amino acids and non-essential based on whether they are synthesized in the body or not.

• Proteins are polymers of amino acids undergo dehydration to form a peptide linkage.
• Dipeptides are formed by a single peptide bond and a tripeptide through two peptide bonds and so on.

In most fungi the structural polysaccharide of cell wall is chitin. In plant cells cell wall is made up of cellulose.

Based on number of amino and carboxyl groups, there are acidic (e.g., glutamic acid), basic (lysine) and neutral (valine) amino acids. Similarly, there are aromatic amino acids (tyrosine, phenylalanine, tryptophan).

Uracil nitrogenous base is produces nucleoside only with ribose sugar. This nucleoside is present only inside the RNA and absent in DNA.

• Primary structure of protein is formed by peptide linkages between two amino acids.
• Secondary structure, i.e. α-Helix and β-Sheath, of protein is formed by hydrogen bonds.
• Tertiary structure of protein is formed by sulphide linkages between different amino acids Quaternary structure is formed when multiple chains of polypeptides held together by hydrogen bonds.