Science Class 12 - Biomolecules Notes

Biomolecules

Welcome to the chapter on Biomolecules for Class 12. In this chapter, you will learn about the different types of biomolecules, their structure, functions, and importance in living organisms. By the end of this chapter, you will understand the role of carbohydrates, proteins, lipids, nucleic acids, and enzymes in life processes.

Introduction

Biomolecules are organic molecules found in living organisms. They are essential for structure, function, and regulation of the body’s tissues and organs.

Types of Biomolecules

• Carbohydrates: Provide energy and structural support.
• Proteins: Build and repair tissues, act as enzymes and hormones.
• Lipids: Store energy, form cell membranes, and act as signaling molecules.
• Nucleic Acids: Store and transfer genetic information (DNA and RNA).
• Enzymes: Biological catalysts that speed up chemical reactions.

Carbohydrates

• Made of carbon, hydrogen, and oxygen.
• Monosaccharides (glucose, fructose), disaccharides (sucrose, lactose), and polysaccharides (starch, cellulose, glycogen).
• Main source of energy for cells.

Proteins

• Made of amino acids linked by peptide bonds.
• Have primary, secondary, tertiary, and quaternary structures.
• Functions: enzymes, hormones, antibodies, structural components.

Lipids

• Include fats, oils, waxes, and steroids.
• Insoluble in water, soluble in organic solvents.
• Functions: energy storage, insulation, cell membrane structure (phospholipids).

Nucleic Acids

• DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
• Made of nucleotides (sugar, phosphate, nitrogen base).
• DNA stores genetic information; RNA helps in protein synthesis.

Enzymes

• Proteins that act as biological catalysts.
• Speed up biochemical reactions without being consumed.
• Have active sites where substrates bind.
• Affected by temperature, pH, and substrate concentration.

Practice Questions

1. What are the building blocks of proteins?
2. Name two functions of lipids in living organisms.
3. What is the difference between DNA and RNA?
4. Give one example each of a monosaccharide and a polysaccharide.
5. How do enzymes speed up chemical reactions?

Challenge Yourself

• Draw the structure of an amino acid and label its parts.
• Explain the lock and key model of enzyme action.

Did You Know?

• Hemoglobin is a protein in red blood cells that carries oxygen.
• Cellulose, a polysaccharide, is the most abundant organic molecule on Earth.

Glossary

• Monosaccharide: Simple sugar molecule (e.g., glucose).
• Amino Acid: Building block of proteins.
• Nucleotide: Building block of nucleic acids.
• Enzyme: Protein that speeds up a chemical reaction.

Answers to Practice Questions

1. Amino acids.
2. Energy storage and forming cell membranes.
3. DNA has deoxyribose sugar and is double-stranded; RNA has ribose sugar and is single-stranded.
4. Glucose (monosaccharide), starch (polysaccharide).
5. By lowering the activation energy needed for the reaction.

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Understanding biomolecules is the key to understanding life itself!