Unit 1: Biomolecules & Bioenergetics

February 20, 2026

Semester 2
BP203T

Introduction to Biomolecules & Bioenergetics

Unit 1 provides the essential vocabulary for all of Biochemistry. You learn about the four major classes of biological molecules: Carbohydrates, Lipids, Nucleic Acids, and Proteins/Amino Acids. You also study the concept of Bioenergetics – specifically how free energy changes drive reactions, and why ATP is the universal energy currency of life.

Download PDF

Syllabus & Topics

  • 1Biomolecules: Introduction and overview.
  • 2Carbohydrates: Classification (Mono, Oligo, Polysaccharides), chemical nature, and biological role.
  • 3Lipids: Classification (Simple, Compound, Derived), chemical nature, and biological role.
  • 4Nucleic Acids: Classification (DNA and RNA), chemical nature, and biological role.
  • 5Amino Acids: Classification (based on R-group: acidic, basic, neutral), chemical nature.
  • 6Proteins: Classification (simple and conjugated), chemical nature, and biological role.
  • 7Bioenergetics: Concept of Free Energy (Gibbs Free Energy, ΔG).
  • 8Endergonic vs Exergonic reactions.
  • 9Relationship between free energy, enthalpy (ΔH), and entropy (ΔS).
  • 10Redox Potential: Concept and importance.
  • 11Energy-rich compounds: Classification.
  • 12ATP: Structure and biological significance.
  • 13Cyclic AMP (cAMP): Structure and role as a second messenger.

Learning Objectives

Classify Biomolecules: Give one example each of a monosaccharide, oligosaccharide, and polysaccharide.
Understand Free Energy: Explain the significance of a negative ΔG (exergonic reaction).
Know ATP: Draw the structure of ATP and explain its energy-releasing hydrolysis.
Role of cAMP: Explain how cAMP acts as a second messenger in hormone signaling.
Amino Acid Classification: Classify amino acids as acidic, basic, or neutral based on their R-groups.

Frequently Asked Questions (FAQs)

Q1. Why is ATP called the energy currency of the cell?

ATP (Adenosine Triphosphate) is called the energy currency because it stores energy in its high-energy phosphoanhydride bonds. When ATP is hydrolyzed to ADP + Pi, it releases about 7.3 kcal/mol (ΔG ≈ –30.5 kJ/mol) of free energy, which is used to drive endergonic (energy-requiring) reactions in the cell.

Q2. What is the difference between DNA and RNA?

  • DNA: Double-stranded, contains deoxyribose sugar, and has the base thymine (T).

  • RNA: Usually single-stranded, contains ribose sugar, and has uracil (U) instead of thymine.

Q3. What are Essential Amino Acids?

Essential amino acids are the nine amino acids that the human body cannot synthesize and must obtain from the diet:
Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and Valine.

Q4. What is Cyclic AMP (cAMP)?

Cyclic AMP (cAMP) is a second messenger formed from ATP by the enzyme adenylyl cyclase. It amplifies hormonal signals (such as adrenaline) that cannot directly enter the cell.

Q5. What is ΔG and why does it matter?

ΔG (Gibbs Free Energy change) indicates whether a reaction is spontaneous:

  • Negative ΔG (exergonic) → Reaction occurs spontaneously.

  • Positive ΔG (endergonic) → Reaction requires energy input.

It is crucial for understanding metabolic pathways and energy flow in biological systems.