Exam Revision Sheet: Biology & Chemistry Fundamentals

1. 📌 Essentials

• Water’s polarity leads to cohesion,, high specific heat, and floating ice.
• Organic molecules: carbohydrates, lipids, proteins nucleic acids.
• Cell theory: all living organisms are made of cells; cells arise from pre-existing cells.
• Enzymes are biological catalysts that lower activation energy.
• Macromolecules are built from monomers via dehydration synthesis.
• Eukaryotic cells contain membrane-bound organelles; prokaryotic cells do not.
• Water is a universal solvent; critical for biochemical reactions.
• Chemical bonds: ionic (transfer), covalent (sharing), hydrogen bonds (polar attraction).
• Cell membrane: phospholipid bilayer, selectively permeable.
• Metabolism includes catabolic (breakdown) and anabolic (build-up) pathways.

2. 🧩 Key Structures & Components

• Water molecule — polar, forms hydrogen bonds, essential for life.
• Carbohydrates — energy source and structural support (e.g., glucose, cellulose).
• Lipids — long-term energy storage, membrane components (fats, phospholipids).
• Proteins — composed of amino acids, perform structural, enzymatic, and transport functions.
• Nucleic acids — DNA and RNA store genetic information.
• Cell membrane — phospholipid bilayer with embedded proteins.
• Mitochondria — ATP production via cellular respiration.
• Chloroplasts — photosynthesis in plant cells.
• Nucleus — contains genetic material.
• Enzymes — proteins that catalyze biochemical reactions.

3. 🔬 Functions, Mechanisms & Relationships

• Water’s hydrogen bonds give it high surface tension and solvent abilities.
• Ionic bonds form salts; covalent bonds form stable molecules.
• Organic molecules polymerize via dehydration synthesis; break down via hydrolysis.
• Enzymes bind specific substrates at active sites, lowering activation energy.
• Cellular processes depend on the hierarchical organization: molecules → organelles → cells.
• Mitochondria and chloroplasts are energy organelles in eukaryotic cells.
• Water’s properties support temperature regulation, transport, and biochemical reactions.
• Cell membrane controls substance flow, maintaining homeostasis.
• Metabolic pathways are interconnected; energy released in catabolism fuels anabolism.

4. Comparative Table: Organic Molecules

5. 🗂️ Hierarchical Diagram

Cell
 ├─ Nucleus
 │    └─ Contains DNA
 ├─ Cytoplasm
 │    ├─ Organelles
 │    │    ├─ Mitochondria (ATP)
 │    │    ├─ Chloroplasts (photosynthesis)
 │    │    ├─ ER (protein/lipid synthesis)
 │    │    ├─ Golgi (modification)
 │    │    └─ Lysosomes (waste)
 │    └─ Cytoskeleton (shape/movement)
 └─ Cell Membrane
      └─ Phospholipid bilayer

6. ⚠️ High-Yield Pitfalls & Confusions

• Confusing covalent vs. ionic bonds; remember: transfer vs. sharing.
• Mistaking water’s density anomaly; ice floats because solid form is less dense.
• Overlooking enzyme specificity; enzymes only catalyze specific substrates.
• Confusing prokaryotic and eukaryotic cell features.
• Assuming all lipids are unhealthy; unsaturated fats are healthier.
• Forgetting that hydrogen bonds are weaker than covalent bonds but crucial for water’s properties.
• Misunderstanding enzyme denaturation; caused by extreme pH or temperature.
• Confusing dehydration synthesis (builds molecules) with hydrolysis (breaks molecules).

7. ✅ Final Exam Checklist

• Water’s properties: polarity, cohesion, adhesion, high heat capacity, solvent role.
• Types of chemical bonds and their significance.
• Major organic molecules: monomers, polymers, functions.
• Cell theory principles.
• Differences between prokaryotic and eukaryotic cells.
• Key organelles and their functions.
• Enzyme structure, function, and factors affecting activity.
• Metabolic pathways: catabolism vs. anabolism.
• Basic biochemical reactions: bonds, energy changes.
• Cell membrane structure and selective permeability.
• Water’s role in temperature regulation and transport.
• Basic molecular structures: sugars, lipids, amino acids, nucleotides.
• Common misconceptions about biological molecules and cell functions.

This revision sheet emphasizes high-yield facts, clear structure, and exam focus, aiding rapid review and memorization.