UNIT 1 BIOLOGY

• Eukaryote


  Cells have cell membrane, cytoplasm and a nucleus
• Prokaryote


  Cells have cytoplasm, cell membrane, cell wall and no nucleus
• Plasmid


  Single loop of DNA found in prokaryotes
• Diffusion


  Particles move from a region where they are in high concentration to where they are in lower concentration
• Osmosis


  Water diffuses from where it is more concentrated, to where it is less concentrated, across a partially permeable membrane
• Active Transport


  The movement of a dissolved substance from a region where it is less concentrated, to a region where it is more concentrated, requiring energy from respiration
• Mitosis


  Cell division for growth and repair
• Meiosis


  Cell division to form gametes
• Gamete


  A sex cell (sperm or egg)
• Differentiation


  When a cell becomes specialised to perform a specific function
• Stem cell


  A cell which has not yet differentiated
• Electron microscope


  • Has a higher resolving power than a light microscope
  • Can study cells in finer detail
  • Better magnification
• Rate of diffusion


  • Affected by difference in concentration
  • Affected by temperature
  • Affected by surface area of the membrane
• Water moves in plant root hair cells

  By osmosis
• Mineral ions move into plant root hair cells


  • By active transport if there aren't many in the soil
  • By diffusion if there is a high concentration of them in the soil
• There are 23 pairs of chromosomes in the nucleus of each human cell
• DNA is in the chromosomes; each chromosome carries a large number of genes
• Mitosis


  1. Cell enlarges

  2. All organelles are copied

  3. The chromosomes replicate

  4. The 2 sets of chromosomes are pulled to opposite sides of the cells

  5. 2 new nuclei form

  6. The cell splits
• Meiosis


  1. The chromosomes replicate

  2. The cell divides twice to make 4 gametes

  3. All gametes are genetically different from each other
• Gametes join at fertilisation


  To make a new cell with the normal number of chromosomes
• The new cell divides by mitosis

  To grow
• Functions of cell organelles


  • Nucleus - stores the DNA
  • Cytoplasm - jelly-like substance where chemical reactions happen
  • Cell membrane - controls what enters and leaves the cell
  • Mitochondria - where respiration happens, to release energy
  • Ribosome - where proteins are made
  • Cell wall - to keep the cell rigid and give it shape
  • Vacuole - a store of sap and nutrients; keeps the cell firm
  • Chloroplast - contains chlorophyll to absorb sunlight for photosynthesis
  • Chromosomal DNA - store of DNA in prokaryotes
  • Plasmid DNA - extra loop of DNA in prokaryotes
  • Flagellum - for movement