Biology

• To work out a microscope magnification you multiply the magnifications of its 2 lenses together. Eg. X5 eyelpeive lens and a x10 objective lens is 5x10= x50
• Micriscopes:

  Milli- ÷1000
• Microscopes

  micro- ÷1000000
• Nano- ÷1000000000
• Pico- ÷1000000000000
• A cell with a nucleus is eukaryotic
• Inside a nucluse is chromosomes which contains DNA
• The cell membrane is like a very thin bag. Controls what enters and leaves, and separates one cell from another.
• Protein breaks down into amino acids
• Starch breakes down into glucose
• Lipid breaks down into fatty acids and glycerol
• Lock and key model show how the enzyme and substrate fit together. The substrate fits into the active site of the enzyme.
• Changes in pH or temptress can affect the enzyme. If the active site changes too much the enzyme can no longer catalyse the reaction. We say the enzyme is denatured
• Amylase - starch to sugar (saliva)
• Lactase - lactose to glucose + galactose (small intestine)
• Change is mass=start mass-final mass ÷ start mass x 100
• Microscope


  Contains two lenses, invented at the end of the 16th century
• Magnification


  How much bigger an object appears compared to its actual size
• Units for very small sizes

  Millimetres (mm), micrometres (μm), nanometres (nm), picometres (pm)
• Magnification


  Multiplying the magnifications of the eyepiece lens and objective lens
• Magnification examples


  • A photo of a water flea magnified ×50
  • A microscope with a ×5 eyepiece lens and ×10 objective lens has a magnification of ×50
• Resolution


  The smallest distance between two points that can still be seen as two points
• Electron microscope


  Uses beams of electrons instead of light to build up an image, can magnify up to ×2 000 000 with resolutions down to 0.0000002 mm
• The highest resolution of electron microscopes is 0.0000002 mm
• Eukaryotic cell


  A cell with a nucleus
• Parts of an animal cell

  • Nucleus (controls the cell and its activities, contains chromosomes with DNA)
  • Cell membrane (controls what enters and leaves, separates one cell from another)
  • Cytoplasm (contains a watery jelly, where most cell activities occur)
  • Mitochondria (jelly-bean shaped structures where aerobic respiration occurs)
  • Ribosomes (tiny round structures that make new proteins)
• Plant cells have additional structures compared to animal cells, including a cell wall, large permanent vacuole, and chloroplasts
• Most human cell nuclei contain two copies of the 23 different types of chromosome, while gametes contain just one copy
• Diploid


  Cells with two sets of chromosomes
• Haploid


  Cells with one copy of each chromosome
• Adaptations of specialised cells

  • Nerve cells are extremely long to carry information quickly
  • Small intestine cells have many tiny folds (microvilli) to increase surface area for absorption
  • Pancreas cells have many ribosomes to make digestive enzymes
  • Muscle cells in the small intestine wall have many mitochondria to provide energy
• Gametes


  Specialised reproductive cells (egg cell and sperm cell)
• Sperm cells are haploid
• Cilia are specialised structures that help move substances
• Nerve cells


  Require a lot of energy
• Specialised cells for reproduction

  During sexual reproduction, two specialised cells (gametes) fuse to create a cell that develops into an embryo
• Human gametes


  The egg cell and the sperm cell
• A human egg cell has a diameter of 0.1 mm
• Fertilisation occurs in the oviducts of the female reproductive system
• Cells in the lining of the oviduct


  • They transport egg cells (or the developing embryos after fertilisation) towards the uterus
  • They are adapted for this function by having hair-like cilia that wave from side to side to sweep substances along