← Biology — Std 11
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Biomolecules

Ch. 6Std 11

Easy Overview

Ever wondered what your body is actually made of? It's not just 'flesh and bones'. It's carbs, proteins, fats, and DNA — all working together. This chapter is about the molecules that make life possible. No, it's not boring chemistry. It's literally what you're made of.

Carbohydrates — Fuel and Structure

Carbs are sugars and their bigger cousins. Glucose is the simplest — it's what your cells burn for energy. Starch is how plants store energy. Cellulose is what plant cell walls are made of — you can't digest it, but cows can. Carbs are made of C, H, and O.

Proteins — The Workers

Proteins do almost everything. They're made of amino acids linked together like beads on a string. There are 20 different amino acids. Enzymes are proteins that speed up reactions. Hair, nails, muscles — all protein. Hemoglobin carries oxygen. Everything gets done by these guys.

Lipids — Fats and Oils

Lipids don't dissolve in water. They're for long-term energy storage and making cell membranes. Fats are made of glycerol and fatty acids. The difference between butter and oil is just saturation — saturated fats are solid at room temp, unsaturated are liquid.

Nucleic Acids — DNA and RNA

DNA holds your genetic blueprint. RNA helps execute it. They're made of nucleotides — each with a sugar, a phosphate, and a nitrogen base. DNA is double-stranded (the famous double helix). RNA is single-stranded. A, T, G, C — those four letters code for everything about you.

Enzymes — The Catalysts

Enzymes make reactions happen faster. Without them, digestion would take years. They work like a lock and key — each enzyme fits a specific molecule. They're not used up in the reaction, so they can work over and over. Temperature and pH affect how well they work.

Key Points

  • •Carbohydrates: sugars and starches, source of energy, structural role.
  • •Proteins: amino acid chains, do most cellular work, enzymes are proteins.
  • •Lipids: fats and oils, energy storage, cell membrane component.
  • •Nucleic acids: DNA (genetic info) and RNA (protein synthesis).
  • •DNA is double-stranded; RNA is single-stranded.
  • •Enzymes are biological catalysts — they speed up reactions.
  • •Lock and key model: each enzyme fits a specific substrate.
  • •Enzymes are sensitive to temperature and pH.

Practice Questions

  • What are the four major types of biomolecules? Give one function of each.
  • Differentiate between DNA and RNA.
  • What are enzymes? Explain the lock and key model.
  • What is the difference between saturated and unsaturated fats?
  • Draw the structure of an amino acid.