GCSE Biology Paper 1

Jul 1, 2024

GCSE Biology Paper 1 Review

Cell Structure and Function

Eukaryotic Cells

  • True nucleus and DNA in chromosomes
  • Includes plant and animal cells
  • Plant cells: Unique organelles
    • Chloroplast: Photosynthesis (contains chlorophyll)
    • Permanent vacuole: Stores cell sap
    • Cell wall: Made of cellulose, provides structure and support
  • Common organelles in both:
    • Mitochondria: Respiration, breaks down glucose
    • Cytoplasm: Site of cellular reactions
    • Cell membrane: Controls entry and exit
    • Ribosomes: Protein synthesis
    • Nucleus: Contains DNA in chromosomes

Specialized Animal Cells

  • Nerve cells (Neurons): Insulating fat sheath, long branches for connections
  • Muscle cells: Many mitochondria, for muscle contraction (three types: smooth, cardiac, skeletal)
  • Sperm cells: Acrosome with enzymes, haploid nucleus, many mitochondria, flagellum (tail)
  • Egg cells (Ova): Many mitochondria, nutrient-rich cytoplasm, haploid nucleus, adaptive cell membrane
  • Ciliated epithelial cells: Wafts mucus in the respiratory system
  • Red blood cells: No nucleus, hemoglobin-rich, biconcave shape for gas exchange

Prokaryotic Cells (Bacteria)

  • Free DNA, sometimes pathogenic or beneficial
  • Key Components:
    • Nucleoid: Free DNA (single loop)
    • Binary fission for division
    • Plasmids: Extra DNA loops, often encode for antibiotic resistance
    • Flagellum: Movement

Specialized Plant Cells

  • Root hair cells: Large surface area, absorbs water/minerals (osmosis, diffusion, active transport)
  • Xylem: Water transport, lignin walls, no end walls, unidirectional flow
  • Phloem: Companion cells for energy, transports sugars and amino acids bidirectionally

Cell Transportation

Mechanisms

  1. Diffusion
  • Passive, high to low concentration, across membrane
  • Common for glucose and gases (CO₂ and O₂)
  1. Osmosis
  • Passive, high to low water concentration, across membrane
  • Practical with plant tissues (mass change as indicator)
  1. Active Transport
  • Active, low to high concentration, across membrane
  • Occurs in root hair cells (ions) and small intestine (glucose)

Cell Division

Mitosis

  • Produces exact genetic copies
  • Steps:
    1. Growth and organelle increase
    2. DNA replication (two chromosome copies)
    3. Chromosomes line up; pulled apart
    4. Nucleus and cell divide
    5. Two genetically identical daughter cells

Meiosis

  • Produces genetically diverse gametes (haploid)
  • Process:
    • DNA replication
    • Two cell divisions
    • Four unique gametes
  • Used in sexual reproduction (sperm and egg)

DNA Structure

  • Double helix polymer of nucleotides (phosphate, deoxyribose sugar, nitrogenous bases)
  • Base pairing: A-T, C-G with hydrogen bonds

Microscopy

Calculations

  • Magnification, object size, and image size triangle (I = A x M)
  • Conversion: mm to µm (×1000) and vice versa

Types of Microscopes

  • Light microscope: Portable, views living specimens, lower resolution
  • Electron microscope: Higher magnification and resolution, for non-living specimens, black and white images

Preparing a slide

  • Thin specimen layer on slide, stained and covered with a cover slip

Enzymes

Characteristics

  • Biological catalysts, proteins, specific to substrates (lock and key model)
  • Sensitive to temperature, pH, and substrate concentration

Reactions

  • Temperature and pH: Optimum point, then denaturation
  • Substrate concentration: Optimum plateau

Key Enzymes

  • Amylase: Starch to glucose
  • Protease: Proteins to amino acids
  • Lipase: Lipids to fatty acids and glycerol

Photosynthesis

  • Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6 O₂ (requires chlorophyll, light)
  • Factors: Light intensity, CO₂ concentration, temperature
  • Uses of Glucose: Stored as starch, cellulose for cell walls, lipids in seeds, respiration, amino acids/proteins for growth

Respiration

Aerobic

  • With oxygen: Glucose → CO₂ + H₂O

Anaerobic

  • Without oxygen: Glucose → lactic acid (muscle fatigue) or fermentation (ethanol + CO₂)

The Immune System

White Blood Cells

  • Phagocytes: Engulf pathogens (phagocytosis)
    • Not specific
  • Lymphocytes: Produce antibodies and antitoxins
    • Specific response
  • Pathogens: Microorganisms causing disease (viruses, bacteria, fungi, protists)

Communicable Diseases

  • Fungal: Athlete's foot, Rose black spot
  • Protist: Malaria
  • Viral: Tobacco mosaic virus, influenza, measles
  • Bacterial: Gonorrhea, Salmonella

Treatments

  • Painkillers: Relieve symptoms, do not cure
  • Antibiotics: Treat bacterial infections, resistance concerns
  • Vaccines: Preventative, stimulate antibody production

Human Physiology

Circulatory System

  • Double system: Blood passes through heart twice
  • Blood Vessels: Capillaries (exchange), veins (low pressure, valves), arteries (high pressure)

Respiratory System

  • Trachea → bronchi → bronchioles → alveoli
  • Gas Exchange: O₂ in, CO₂ out by diffusion

Digestive System

  • Enzymes in small intestine (duodenum, jejunum, ileum)
  • Villi/microvilli for increased absorption

Non-Communicable Diseases

  • Cancer: Benign (non-cancerous), malignant (cancer spread)
  • Coronary Heart Disease: High cholesterol, leads to heart attack