Question

Differentiate between the following :
(i) Acidic amino acids and basic amino acids
(ii) Nucleotide and Nucleoside

Hint:

Memory aid: Nucleo{s}ide = {S}ugar + Base. Nucleo{t}ide = {T}ri-component (Sugar + Base + Phosphate).

Answer 1

(i) Acidic amino acids and Basic amino acids

Acidic amino acids:
- Acidic amino acids contain a carboxyl group (-COOH) in their side chain, which can donate a proton (H+) and thus makes them acidic.
- Examples of acidic amino acids are Aspartic acid (Asp) and Glutamic acid (Glu).
- They have a negative charge at physiological pH due to the deprotonation of the carboxyl group in the side chain.

Basic amino acids:
- Basic amino acids contain an amino group (-NH₂) in their side chain, which can accept a proton (H+) and thus makes them basic.
- Examples of basic amino acids are Lysine (Lys), Arginine (Arg), and Histidine (His).
- They have a positive charge at physiological pH due to the protonation of the amino group in the side chain.

(ii) Nucleotide and Nucleoside

Nucleotide:
- A nucleotide is a basic building block of nucleic acids like DNA and RNA.
- It consists of a nitrogenous base (purine or pyrimidine), a pentose sugar (ribose or deoxyribose), and one or more phosphate groups.
- Example: Adenosine triphosphate (ATP) is a nucleotide, which contains adenine as the nitrogenous base, ribose as the sugar, and three phosphate groups.

Nucleoside:
- A nucleoside consists of a nitrogenous base and a pentose sugar (ribose or deoxyribose), but it does not contain any phosphate group.
- It is the precursor to a nucleotide, which gains one or more phosphate groups to form a nucleotide.
- Example: Adenosine is a nucleoside, which contains adenine as the nitrogenous base and ribose as the sugar.