Biology - Chapter 9: Biomolecules
Understanding Proteins, Carbohydrates, Lipids, and Enzymes
1. Classification of Biomolecules
All organic compounds found in living organisms are called biomolecules. They are classified into two main categories:
| Category | Molecular Weight | Examples |
|---|---|---|
| Biomicromolecules | 18 – 800 Daltons | Amino acids, Sugars, Nucleotides |
| Biomacromolecules | More than 10,000 Daltons | Proteins, Polysaccharides, Nucleic Acids |
💡 Quick Concept:
Small molecules = Micromolecules
Large complex molecules = Macromolecules
2. Important Questions & Answers
Q1. What are amino acids? Why are they called zwitterions?
Answer: Amino acids are the building blocks of proteins.
They contain both an amino group (-NH₂) and a carboxyl group (-COOH).
At certain pH levels, they carry both positive and negative charges, hence called zwitterions.
Zwitterion Structure
Q2. What are the four levels of protein structure?
Answer:
• Primary → Sequence of amino acids
• Secondary → Alpha-helix / Beta-sheet
• Tertiary → 3D folding
• Quaternary → Multiple polypeptide chains
• Primary → Sequence of amino acids
• Secondary → Alpha-helix / Beta-sheet
• Tertiary → 3D folding
• Quaternary → Multiple polypeptide chains
Q3. Explain the lock and key model of enzyme action.
Answer: Enzymes have a specific active site where only a particular substrate fits, like a key in a lock.
This forms an enzyme-substrate complex and converts it into products.
Lock and Key Model
Q4. What are the components of a nucleotide?
Answer:
1. Nitrogenous base 2. Pentose sugar (Ribose/Deoxyribose) 3. Phosphate group
1. Nitrogenous base 2. Pentose sugar (Ribose/Deoxyribose) 3. Phosphate group
Q5. Describe the DNA model proposed by Watson and Crick.
Answer: DNA has a double helix structure.
Two strands run in opposite directions.
Base pairing: A = T and G = C.
Q6. Factors affecting enzyme activity?
Answer:
• Temperature
• pH
• Substrate concentration
• Temperature
• pH
• Substrate concentration
🔥 Exam Booster:
Protein = Amino acids
DNA = Genetic material
Enzymes = Biocatalysts