Problem 60 - Objective Biology for NEET

Question

Sugar + Nitrogen bases + Phosphate forms (a) Nucleoside (b) Nucleotide (c) Peptide (d) Glycoside

Step-by-Step Solution

Answer

The combination of Sugar + Nitrogen bases + Phosphate forms a Nucleotide.

Step 1: Understanding molecular composition

First, one should understand what molecule each option represents. A Nucleoside is made up of a sugar and a nitrogenous base. A Nucleotide is made of a sugar, a nitrogenous base and a phosphate group. A Peptide is a short chain of amino acids, and a Glycoside consists of a sugar and another component often a non-sugar substance.

Step 2: Comparing given molecules to options

Next, compare the molecules given in the question (Sugar + Nitrogen bases + Phosphate) to the compositions defined in step 1. It can be seen that these molecules match with the composition of a Nucleotide.

Step 3: Conclusion

Therefore, Sugar + Nitrogen bases + Phosphate forms a Nucleotide. None other options match the molecular structure given in the question.

Key Concepts

Molecular Composition

Understanding the molecular composition of different biomolecules is key to grasping the foundations of biochemistry. Molecules are made up of atoms joined together by various bonds.
These can include covalent bonds, ionic bonds, and hydrogen bonds. Within living organisms, the molecular composition often refers to how atoms like carbon, nitrogen, hydrogen, oxygen, and others come together to form compounds.
Some common biomolecules formed include nucleotides, peptides, and glycosides.

• Nucleotides are made of three components: a sugar, a phosphate group, and a nitrogenous base.
• Peptides are formed from amino acids linked by peptide bonds.
• Glycosides involve a sugar and at least one other component, often non-sugar.

By comparing these molecular compositions, one can determine the identity and functionality of the compound.

Nucleoside

A nucleoside is a fundamental structural component in the biochemistry of nucleic acids. Despite sounding similar to a nucleotide, it's important to distinguish between the two.
A nucleoside is composed of two parts:

• A sugar (which is either ribose or deoxyribose).
• A nitrogenous base (such as adenine, guanine, cytosine, thymine, or uracil).

Unlike nucleotides, nucleosides do not contain a phosphate group. This difference is crucial, as the presence of the phosphate group in nucleotides is what allows them to form chains, such as those found in DNA and RNA.

Peptide

Peptides are small chains of amino acids that create the building blocks of proteins. They are formed when two or more amino acids are bonded together by peptide bonds.
These bonds occur between the carboxyl group of one amino acid and the amino group of another, releasing a molecule of water in the process.
The basic molecular structure of a peptide looks like: \[ H_2N - CH(R_1) - COO^- + NH_3^+ - CH(R_2) - COOH \]
where R1 and R2 are side chains specific to each amino acid. Peptides can be classified by the number of amino acids:

• Dipeptides contain two amino acids.
• Oligopeptides have a few amino acids.
• Polypeptides consist of many amino acids and can fold into functional proteins.

Understanding peptides helps us appreciate their role in forming proteins and contributing to various biological processes.

Glycoside

Glycosides are crucial in biology, particularly in the storage and transport of energy in cells. A glycoside encompasses two parts:

• A sugar molecule, which can be glucose, fructose, or others.
• An aglycone, which is a non-sugar component that can be another type of molecule like a sterol or alcohol.

The bond between the sugar and the aglycone is called a glycosidic bond. This bond is formed through a condensation reaction, releasing a molecule of water.
Glycosides are important in various biological functions, including signaling and defense mechanisms in plants. Some glycosides contribute to the bright colors in flowers and fruits, while others act as defensive compounds against herbivores.