🔬 Metabolism

• Definition: The sum of all chemical reactions occurring within a cell or organism to maintain life.

• Types:

  • Catabolism: Breaks down complex molecules into simpler ones, releasing energy. Example: breakdown of glucose in cellular respiration.

  • Anabolism: Builds complex molecules from simpler ones, requiring energy. Example: protein synthesis.

• Importance: Helps maintain homeostasis, allowing the body to adapt and respond to changes.

💧 Osmosis

• Definition: Passive movement of water molecules across a semi-permeable membrane from a region of low solute concentration to high solute concentration.

• Key Effects:

  • In a hypertonic solution: water exits the cell → cell shrinks.

  • In a hypotonic solution: water enters the cell → cell swells or bursts.

  • In an isotonic solution: no net water movement → cell stays the same.

🧪 Membrane Transport

• The cell membrane is selectively permeable and controls movement of substances in/out of the cell.

Passive Transport (no energy required):

1. Simple Diffusion: Small, non-polar molecules move freely (e.g., O₂, CO₂).

2. Facilitated Diffusion: Larger/polar molecules (e.g., glucose, ions) move via specific protein channels.

Active Transport (requires ATP):

• Moves substances against the concentration gradient.

• Sodium-Potassium Pump (Na⁺/K⁺ ATPase): Actively pumps 3 Na⁺ out and 2 K⁺ into the cell, crucial for nerve impulses and cell potential.

Bulk Transport:

• Endocytosis: Cell engulfs substances (e.g., food, pathogens).

• Exocytosis: Vesicles release substances out of the cell (e.g., hormones).

⚛️ Biochemistry & Cellular Chemistry

• Biomolecules:

  • Carbohydrates: Provide energy (e.g., glucose), stored as glycogen (animals) or starch (plants).

  • Proteins: Composed of amino acids; involved in structure, transport (e.g., hemoglobin), and enzymes.

  • Lipids: Include fats and phospholipids; key in energy storage and forming cell membranes.

  • Nucleic Acids: DNA and RNA; store and transmit genetic information.

• Enzymes:

  • Act as biological catalysts, speeding up reactions by lowering activation energy.

  • Highly specific to substrates; affected by temperature, pH, and substrate concentration.

  • Work via models like lock and key or induced fit.