Biology Paper 1 Notes and Flashcards

1. Cell Structure and Function

  • Plant Cell

    • Cell Membrane: Controls movement in and out of the cell.

    • Cell Wall: Provides structure and support.

    • Vacuole: Helps maintain structure and stores substances.

    • Cytoplasm: Site of most cellular reactions.

    • Ribosomes: Sites of protein synthesis.

    • Chloroplasts: Responsible for photosynthesis (green).

    • Mitochondria: Energy production (pink).

    • Nucleus: Control center containing DNA.

  • Animal Cell

    • Similar components to plant cells but lack cell wall, vacuole, and chloroplasts.

  • Bacterial Cell

    • Cell Membrane: Controls movement in and out of the cell.

    • Cytoplasm: Site of reactions.

    • Chromosome: Contains DNA; not enclosed in nucleus.

    • Flagella: Used for locomotion.

    • Cell Wall: Provides structure.

2. Cellular Differentiation and Specialization

  • All cells initially have a similar structure.

  • Cells differentiate based on gene activation, leading to various specialized cells such as:

    • Neurons: Long axons for signaling.

    • Muscle Cells: Contract and relax to enable movement.

    • Villi Cells: Increase surface area for absorption.

3. Microscopy and Measurement

  • Historical range from basic lenses to advanced electron microscopes.

  • Magnification Calculation: Magnification = Image Height / Object Height.

4. DNA Structure

  • DNA: Long strand of deoxyribonucleic acid twisted into a double helix and packaged into chromosomes located in the nucleus.

5. Cell Division

  • Mitosis: Process of cell division resulting in two identical daughter cells. Steps include:

    1. Condensation of DNA into chromosomes.

    2. Alignment of chromosomes.

    3. Separation of chromosomes to opposite ends.

    4. Formation of new nuclei and division of the cell.

6. Stem Cells

  • Stem cells can differentiate into any cell type and have potential in medical applications like:

    • Treating Parkinson's disease and spinal injuries.

    • Growing organs for transplants.

  • Controversial due to ethical concerns surrounding embryo creation and destruction.

7. Transport Mechanisms

  • Diffusion: Movement from high to low concentration (e.g., oxygen and carbon dioxide exchange in lungs and gut absorption).

  • Osmosis: Movement of water across a partially permeable membrane from high water concentration to low.

  • Active Transport: Movement against concentration gradient using energy (e.g., glucose absorption in the gut).

8. Hierarchy of Biological Organization

  • Cells: Basic building blocks.

  • Tissues: Groups of similar cells performing a function.

  • Organs: Composed of different tissues working together.

  • Organ Systems: Groups of organs collaborating for specific functions (e.g., Digestive System).

9. Digestive System Overview

  • Mouth: Mechanical breakdown of food.

  • Salivary Glands: Produce amylase for starch digestion.

  • Liver: Produces bile to emulsify fats.

  • Stomach: Breaks down food using acid and enzymes.

  • Small Intestine: Main site for nutrient absorption.

  • Large Intestine: Absorbs excess water, excretes waste.

10. Digestive Enzymes

  • Lipase: Breaks down fats into fatty acids and glycerol (produced in pancreas and small intestine).

  • Protease: Breaks down proteins into amino acids (produced in stomach and pancreas).

  • Amylase: Converts starch into sugars (produced in salivary glands and pancreas).

  • Lock and Key Mechanism: Specific enzymes fit specific substrates to form enzyme-substrate complexes, leading to the reaction.