Class 11 Biology Chapter 9 Biomolecules – Revision Notes

Biomolecules – carbohydrates, proteins, lipids, and nucleic acids – make up this chapter’s core, alongside how enzymes function as biological catalysts.

Last Updated: September 23, 2026

Carbohydrates

• Mono-, oligo-, poly-saccharides. Starch (plant), glycogen (animal) storage; cellulose structural.

Proteins

• Amino acids linked by peptide bonds.
• Structure: primary, secondary, tertiary, quaternary.

Lipids and Nucleic Acids

• Lipids: fatty acids, triglycerides, phospholipids, steroids.
• DNA (deoxyribose, A/T/G/C) vs RNA (ribose, A/U/G/C).

Enzymes

• Biological catalysts (mostly protein); lower activation energy; affected by temperature, pH, substrate concentration.

One-Line Summary

Biomolecules — carbohydrates, proteins, lipids, and nucleic acids — are the chemical building blocks of life, with enzymes (mostly proteins) catalyzing the biochemical reactions that sustain cellular metabolism.

Frequently Asked Questions

What are the four major classes of biomolecules discussed in this chapter?
The chapter covers carbohydrates, proteins, lipids, and nucleic acids, each performing distinct roles such as energy storage, structural support, catalysis, and carrying genetic information.

What determines the specific shape and function of a protein?
The sequence of amino acids in a protein, known as its primary structure, folds into a unique three-dimensional shape through hydrogen bonds and other interactions, and this final shape determines the specific function of the protein.

Written by Satish

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