Bio paper 1

• Light Microscopes


  They are cheap to make
• Light Microscopes


  They allow you to see the outlines of cells
• Electron microscopes


  They allow you to visualise finer details including organelles
• Electron microscopes have greater resolving power than light microscopes
• Image size


  It is measured in micrometers (μm)
• Typical cell size is 8-33 μm long
• Converting micrometers to millimeters

  Divide by 1000
• Mitochondria

  Site of cellular respiration
• Nucleus


  Contains genetic material, including DNA, which controls the cell's activities
• Cytoplasm


  Jelly-like material where many of the chemical reactions happen
• Mitochondria


  Site of cellular respiration
• Cell membrane


  Controls the movement of substances in and out of the cell
• Ribosomes


  Organelle where protein synthesis occurs
• Cell wall


  Made from cellulose, strengthens the cell and supports the plant
• Chloroplast

  Contains the green pigment, chlorophyll, absorbs light energy for photosynthesis
• Vacuole


  Filled with cell sap to help keep the cell turgid
• Magnification

  The ability to make small objects seem larger
• Resolution

  The ability of a microscope to distinguish detail
• Microscopes


  • Light Microscope
  • Electron Microscope
• Light Microscope uses focused light and lenses to magnify
• Electron Microscope uses a beam of accelerated electrons to magnify
• What does a plant cell have that an animal cell does not

  -cell wall

  -chloroplast

  -vacuole
• Bacteria reproduce by binary fission they divide every 10 minutes
• Making cultures with aseptic technique practicle:

  1. Lift lid of petri dish towards flame
  2. put drop of culture on agar/ spread evenly
  3. put discs of antibiotics on culture
  4. few bits of tape to allow aerobic respiration, incubate at 25*c
  5. measure size of cultures/ areas with no bacteria
• All human cells have 23 pairs of chromosomes (diploid) except gametes (eggs/sperm) that have just 23 (haploid)
• New diploid cells are mad by mitosis, for growth and repair
• Mitosis process

  1. nucleus dissolves and genetic material is duplicated
  2. the two sets of chromosomes move to different sides
  3. mitochondria ribosomes and other organelles are duplicated
  4. the cell divides producing two identical diploid cells
• Stem cells can specialise to perform specific functions

  they are found in animal embryos and plant meristems
• Stem cells can be made from your bone, blood, embryo, clones
• Stem cells can be used to treat conditions
• Cloning


  Produces cells associated with desired traits
• Cloning can be used to preserve species or crops with desired traits
• Diffusion is the movement of particles from an area of high concentration to an area of low concentration.

  this is passive as it requires no energy
• Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
• Osmosis practical

  1. weigh and place identical cylinders from same vegetable in sugar solutions of varying concentrations
  2. after set time remove excess water and reweigh, calculate % change in made
  3. plot % change in mass against concentration
• Active transport is the movement of molecules from an area of low concentration to an area of high concentration against a concentration gradient
• Organisation

  1. cell (e.g. Heart cell)
  2. tissue (heart tissue)
  3. organ (heart)
  4. organ system (circulatory system)
• Digestive system- 1. mouth

  teeth break down food mechanically: saliva contains amylase
• Digestive system- 2. liver

  the liver produces bile which is stored in gall bladder before going to the small intestine

  bile emulsifies lipids to form droplets increasing their surface area
• Digestive system- 3. stomach

  stomach contains hydrochloric acid and enzymes that chemically break down food