Key Concepts in Biology

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  • Section 1 - Key Concepts in Biology
    • Cells
      • Eukaryotic cells are complex and Prokaryotic cells are simple
      • Suncellular structures
        • Animal cells: nucleus, cytoplasm, cell membrane, mitochondria, ribosomes
        • Plant cells also have: cell wall, vacuole, chloroplasts (photosynthesis)
      • Bacterial cells: chromosomal DNA, ribosomes, cell membrane, plasmid DNA, flagellum
    • Specialised Cells
      • Structure makes them adapted to function
        • egg cell: nutrients - cytoplasm, haploid nucleus, membrane stops any more sperm entering after fertilisation
        • sperm cell: long tail, haploid nucleus, mitochondria, acrosome
        • epithelial cells line organs - move substances
      • nucleus of egg cell and sperm cell fuse - fertilised egg - embryo
        • haploid cells combine - right number of chromosomes
    • Microscopy
      • better resolution = more detail
      • light microscope passes light through specimen to see sub-cellular structures
        • electron microscopes have higher resolution and magnification
      • total magnification = eyepiece lens magnification x objective lems magnification
      • magnification = image size / real size
      • standard form & unit conversion
    • Enzymes
      • biological catalysts - higher temperature
      • key & lock - enzymes with active site have high specifity for substrate
      • temperature increases reaction rate until a certain point - denatures
      • optimum pH (often neutal 7)
      • faster reaction with higher substrate concentration
      • rate = 1000 / time
    • Breakdown and Synthesis
      • Proteins, Lipids, Carbohydrates broken down to digest easily
      • carbohydrases > carbohydrates > simple sugars
      • Protease > proteins > amino acids
      • Lipases > lipids > glycerol & fatty acids
      • Enzymes catalyse reactions needed to synthesise molecules from smaller components
    • Diffusion, Osmosis, Active Transport
      • Diffusion is the net movement of particles from an area of high concentration to an area of lower concentration
      • Osmosis is the net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
      • Active transport is the movement of particles across a membrane against a concentration gradient using energy transferred during respiration


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