GCSE Science Quick-Revision Notes

Biology

  • Cell types

    • Eukaryotic – DNA inside nucleus (animal, plant, fungus)
    • Prokaryotic – DNA free in cytoplasm (bacteria)

  • Organelles

    • Nucleus – controls cell
    • Mitochondria – aerobic respiration
    • Ribosomes – protein synthesis
    • Chloroplasts – photosynthesis (contains chlorophyll)
    • Permanent vacuole – cell sap, rigidity

  • Membrane transport

    • Diffusion – particles high → low concentration
    • Osmosis – water through partially permeable membrane low solute → high solute conc.
    • Active transport – low → high conc., energy required
    • Partially permeable membrane – selective passage

  • Microscopy

    • Magnification=ImageRealMagnification = \frac{Image}{Real}
    • Magnification – scale factor; Resolution – ability to distinguish close points

  • Specialised cells

    • Animal – sperm, nerve, muscle
    • Plant – xylem, phloem, palisade
    • Adaptations = structural features enabling function

Organisation & Cell Reproduction

  • Biological hierarchy: Organelles → Cells → Tissues → Organs → Organ Systems → Organism
  • Mitosis sequence: Interphase → Mitosis → Cytokinesis
    • Interphase – DNA & organelles replicate
    • Mitosis – chromosomes align, chromatids pulled apart
    • Cytokinesis – cytoplasm/ membrane divide → 2 identical cells
  • Meiosis listed as second type of cell reproduction (detail not given)
  • Stem cells
    • Undifferentiated; Differentiation = becoming specialised
    • Plant meristems (root/shoot tips)
    • Embryonic (≤4 weeks) – pluripotent
    • Adult – multipotent (tissue-specific)
    • Therapeutic cloning – embryo genetically identical to patient

Physics

  • Key quantities

    • Energy – ability to do work
    • Power – rate of energy transfer

  • Energy stores

    • Gravitational potential, Kinetic, Thermal, Elastic, Electrostatic
    • Conservation of energy – cannot be created or destroyed, only transferred

  • Work & transfers

    • Mechanical work – force moves object
    • Electrical work – charge moves through potential difference
    • Radiation – energy transfer by electromagnetic waves

  • Other terms

    • Useful energy store – energy used for intended purpose
    • Friction – resistive force between surfaces

Chemistry

  • Basic particles & substances

    • Atom, Molecule, Element, Compound, Mixture
    • Isotope – same protons, different neutrons
    • Ion – atom that gained/lost electrons

  • Conservation of mass – total mass unchanged in reactions

  • Sub-atomic particles

    • Proton +1+1, Neutron 00 (nucleus); Electron −1-1 (shells)

  • Other definitions

    • Solvent – liquid that dissolves solute; Solubility – amount dissolvable
    • Filtration – separate insoluble solid
    • Boiling – liquid → gas; Condensation – gas → liquid
    • Reactants – starting substances; Products – formed substances
    • Mass number = protons + neutrons

Periodic Table & Groups

  • Atomic number – number of protons; basis of modern ordering

  • Outer electrons = group number; Period = electron shells

  • Newlands’ law of octaves – repeating properties every 8 when ordered by mass

  • Metals – left of staircase from Al; Non-metals – right

  • Ions: Cations (+), Anions (−)

  • Group 1 Alkali metals

    • React with water → metal hydroxide + hydrogen
    • Word: Alkali metal + water → metal hydroxide + hydrogen
    • Symbol: 2M+2H<em>2O→2MOH+H</em>22M + 2H<em>2O \rightarrow 2MOH + H</em>2
    • Reactivity ↑ down group (shielding & atomic radius ↑, nuclear attraction ↓)

  • Group 7 Halogens

    • "Salt makers"; reactivity ↓ down group
    • States: F, Cl gases; Br liquid; I & below solids
    • Colours: F yellow, Cl green, Br orange, I purple

  • Reactivity factors

    • Nuclear attraction – pull of nucleus on outer electrons
    • Shielding – inner shells reduce attraction
    • Atomic radius – distance nucleus → outer shell