WJEC GCSE Biology Complete Specification Study Guide

1.1 Cells and Movement Across Cell Membranes

  • Cell Structure: Recognition of animal and plant cell parts: cell membrane, cytoplasm, nucleus, mitochondria, cell wall, chloroplast, and vacuole.

  • Microscopy: Use of a light microscope to view cells; production of labelled scientific diagrams.

  • Specialised Cells: Understanding cell differentiation in multicellular organisms.

  • Levels of Organisation: Tissues (similar cells/function), organs (several tissues), and organ systems working as an organism.

  • Diffusion: Movement of substances down a concentration gradient; the cell membrane's role; Visking tubing as a living material model (membrane pore/particle size).

  • Passive Process: Diffusion allows specific substances (oxygen, carbon dioxide) through the membrane.

  • Osmosis: Diffusion of water through a selectively permeable membrane from high water (low solute) concentration to low water (high solute) concentration.

  • Active Transport: An active process allowing substances to enter cells against a concentration gradient.

  • Enzymes: Proteins made by cells that speed up (catalyse) reactions.

    • Composed of amino acids folded into specific shapes.

    • Active Site: Specific shape determines function; understood through 'lock and key' modelling.

    • Molecular collisions: Result in enzyme-substrate complexes.

    • Factors: Effect of temperature and pH; boiling denatures most enzymes.

1.2 Respiration and the Respiratory System in Humans

  • Aerobic Respiration: Series of enzyme-controlled reactions using glucose and oxygen to release energy (ATPATP), carbon dioxide, and water.

    • Word Equation: Glucose+Oxygen→Carbon Dioxide+Water+(Energy)\text{Glucose} + \text{Oxygen} \rightarrow \text{Carbon Dioxide} + \text{Water} + (\text{Energy})

  • Anaerobic Respiration: Occurs without oxygen; glucose breaks down into lactic acid and energy. It is less efficient (incomplete breakdown, less ATPATP) and results in oxygen debt.

    • Word Equation: Glucose→Lactic Acid+(Energy)\text{Glucose} \rightarrow \text{Lactic Acid} + (\text{Energy})

  • Anatomy: Nasal cavity, trachea, bronchi, bronchioles, alveoli, lungs, diaphragm, ribs, and intercostal muscles.

  • Mechanisms:

    • Inspiration/Expiration: Changes in thoracic volume and pressure driven by the diaphragm and rib cage.

    • Bell Jar Model: Used to illustrate breathing but has limitations.

  • Gas Exchange: Alveoli structure (moist lining, capillary wall, red blood cells, plasma); differences between inspired and expired air percentages; use of limewater to detect CO2CO_2.

  • Smoking Effects: Damage to cilia and mucus; links to lung cancer and emphysema.

1.3 Digestion and the Digestive System in Humans

  • Nutrient Breakdown: Large insoluble molecules to small soluble products:

    • Fats →\rightarrow Fatty acids and glycerol (provide energy).

    • Proteins →\rightarrow Amino acids (build body proteins).

    • Starch →\rightarrow Glucose (provides energy or stored as glycogen).

  • Food Tests:

    • Starch: Iodine solution.

    • Glucose: Benedict’s reagent.

    • Protein: Biuret solution.

  • Enzymes: Role of carbohydrase, protease, and lipase.

  • Anatomy: Mouth, oesophagus, stomach, liver (secretes bile), gall bladder (stores bile), bile duct, pancreas, small intestine, large intestine, anus.

  • Peristalsis: Movement of food through the system.

  • Absorption: Soluble substances pass through the small intestine wall; Visking tubing used as a model gut.

  • Balanced Diet: Requirement for protein, carbohydrates, fats, minerals (iron), vitamins (Vitamin C), fibre, and water. Effects of excess sugar, salt, and fat (stored as fat).

1.4 Circulatory System in Humans

  • Blood Components: Red blood cells (biconcave, transport oxygen), white cells (phagocytes and lymphocytes), platelets (clotting), and plasma.

  • Heart Structure: Four chambers (left/right atria and ventricles), valves (tricuspid, bicuspid, semi-lunar), and major vessels (pulmonary artery/vein, aorta, vena cava, coronary vessels).

  • Double Circulation: Pulmonary system (lungs) and systemic system (organs).

  • Blood Vessels:

    • Arteries: High pressure, carry blood away from heart.

    • Veins: Low pressure, carry blood to heart, have valves.

    • Capillaries: Thin walls for diffusion/exchange.

  • Cardiovascular Disease (CVD): Treatments including statins, angioplasty, and lifestyle changes (diet/exercise).

1.5 Plants and Photosynthesis

  • Process: Using chlorophyll to absorb light to convert carbon dioxide and water into glucose and oxygen.

    • Word Equation: Carbon Dioxide+Water→Light/Chlorophyll→Glucose+Oxygen\text{Carbon Dioxide} + \text{Water} \rightarrow \text{Light/Chlorophyll} \rightarrow \text{Glucose} + \text{Oxygen}

  • Limiting Factors: Temperature, CO2CO_2 concentration, and light intensity.

  • Leaf Structure: Cuticle, epidermis, stomata (guard cells), palisade layer, spongy layer, xylem, and phloem.

  • Transport:

    • Xylem: Water transport; significance of root hairs and osmosis.

    • Phloem: Carrying sucrose for respiration or starch storage.

    • Transpiration: Movement of water through the plant and evaporation from leaves.

  • Nutrients: Nitrates (growth), Potassium (yellow leaves if deficient), Phosphate (root growth); use of NPK fertilisers.

1.6 Ecosystems, Nutrient Cycles and Human Impact

  • Food Chains/Webs: Producers, consumers (1st, 2nd, 3rd stage), herbivores, carnivores, and decomposers.

  • Energy Transfer: Energy used for growth/repair; lost via waste and respiration.

  • Pyramids: Pyramids of numbers and biomass; calculation of energy transfer efficiency.

  • Material Cycling:

    • Carbon Cycle: Photosynthesis, respiration, and combustion of fossil fuels.

    • Nitrogen Cycle: Decomposers (proteins/urea to ammonia), nitrifying bacteria (ammonia to nitrates), nitrogen fixation (air to nitrates), and denitrification.

  • Human Impact: Intensive farming (fertilisers, pesticides, battery methods), pollution indicators (lichens for air, indicator species/O2O_2 levels for water), and bioaccumulation of heavy metals.