Edexcel International GCSE Biology Crash Course

Introduction

Cells: Basic unit of life
- Visible under light microscope; subcellular structures visible under electron microscope
- Magnification: Image size / Object size
Cell types:
- Eukaryotic: Contain nucleus (e.g., plant and animal cells)
- Prokaryotic: No nucleus, DNA in plasmid ring (e.g., bacteria)
Organelles:
- Cell membrane: Semi-permeable
- Cell wall: Rigid structure in plant cells and bacteria
- Cytoplasm: Site of chemical reactions
- Mitochondria: Respiration, energy release
- Ribosomes: Protein synthesis
- Chloroplasts: Photosynthesis in plant cells
- Vacuole: Stores sap in plant cells
Specialization: Cells adapt for specific functions (e.g., nerve, muscle, root hair cells)
Stem cells: Unspecialized cells that can differentiate
- Found in embryos and bone marrow (limited to blood cells)
- Applications in medicine (e.g., combating diabetes, paralysis)
Cloning: Ethical considerations, preventing species extinction, producing specific crops

Diffusion: Molecules move from high to low concentration (passive)
Osmosis: Diffusion of water across a semi-permeable membrane
Active Transport: Carrier proteins use energy to move substances against gradient
Tissues, Organs, Systems:
- Tissues: Groups of similar cells
- Organs: Groups of tissues
- Systems: Groups of organs (e.g., circulatory, digestive systems)
Digestive System: Breaks down food into nutrients
- Enzymes: Biological catalysts, specific to substrates (e.g., amylase, proteases, lipases)
- Practical on enzymes: Optimal conditions for enzyme activity
Balanced Diet:
- Carbohydrates: Energy
- Fats: Energy
- Proteins: Growth, repair
- Vitamins & Minerals: Health maintenance (e.g., vitamin C, D, calcium, iron)
Respiratory System: Breathing and gas exchange
- Pathway: Trachea → Bronchi → Bronchioles → Alveoli
- Heart and Circulatory System: Double circulation, heart chambers, blood vessels
- Blood Components: Red cells, white cells, platelets, plasma
Plants:
- Photosynthesis: Light energy to chemical energy
- Leaf Structure: Cuticle, epidermis, mesophyll, veins, stomata
- Transportation: Xylem (water) and phloem (sugars)

Cell Division: Mitosis and meiosis
- Mitosis: Cell division for growth and repair
- Meiosis: Produces gametes for sexual reproduction
Genetics:
- DNA Structure: Double helix, nucleotides
- Genes and Chromosomes: Genotype vs. phenotype
- Inheritance: Dominant and recessive alleles, Punnett squares
- Genetic Disorders: Polydactyly, cystic fibrosis
- Sex determination: XX (female), XY (male)
Evolution:
- Natural Selection: Survival of the fittest
- Mutations: Genetic variations
- Speciation: Formation of new species
Biotechnology:
- Selective Breeding: Enhancing traits
- Genetic Modification: Engineered traits (e.g., insulin production)
- Cloning: Ethical implications, techniques

Ecosystems:
- Biotic and Abiotic Factors: Living vs. non-living components
- Interdependence: Organisms rely on each other
- Population Studies: Quadrats, transects
Food Chains and Webs:
- Trophic Levels: Producers, consumers, apex predators
- Pyramid of Biomass: Energy flow and loss
Cycles:
- Carbon Cycle: Photosynthesis, respiration, decomposition
- Water Cycle: Evaporation, precipitation, runoff
- Nitrogen Cycle: Fixation, nitrification, denitrification
Conservation:
- Biodiversity: Importance, threats, preservation methods
- Human Impact: Pollution, deforestation, climate change
- Sustainable Practices: Fishing, agriculture

Food Production:
- Agriculture: Crop biotechnology, pest control
- Aquaculture: Sustainable fishing techniques
Medical Applications:
- Genetics: Screening, personalized medicine
- Transplants: Organ and tissue engineering
Industrial Applications:
- Bioprocessing: Fermentation, enzyme technology
- Energy Production: Biofuels, biogas

Comprehensive overview of key biology topics
Essential for understanding cellular processes, genetics, ecology, and biotechnology
Insight into practical applications and ethical considerations in biology