Cell Biology

• Why is the cover slip lowered at an angle?


  To prevent air bubbles
• Why is only a thin layer of epidermis used?


  To help see individual cells
• Mitosis


  Genetic material is replicated

  Replicated chromosomes are pulled apart

  Cytoplasm divides into two cells
• Adaptations of gills for gas exchange

  Large surface area

  Lots of blood capillaries

  Thin surface layer
• Chromosome

  coiled up lengths of DNA molecules containing genetic information
• Stem Cells

  undifferentiated cells that have the ability to develop into different types of specialized cells in the body.
• Undifferentiated Cell Function

  repairing and replacing damaged cells
• Stem cell research: For vs Against


  Could cure existing sufferers

  Most of the stem cells used would be destroyed anyway

  Embryos could be a human life
• Therapeutic cloning


  the embryo could be made to have the same genetic information as a parent. This would make sure the cells are rejected by the patients body
• Light Microscopes

  Use light and lenses to form an image

  Can see individual cells and structures
• Binary Fission


  Circular DNA and plasmids replicate

  Circular DNA strands move to opposite side of cell

  Cytoplasm begins to divide and new cell wall begins to form

  Cytoplasm divides so 2 new daughter cells are produced
• Electron microscopes


  use image to form an electron

  higher magnification and resolution

  can see internal structures
• What affects the rate of diffusion 


  Surface area

  Temperature

  Concentration gradient
• How exchange surfaces are adapted to maximise effectiveness


  thin membrane

  large surface area

  lots of blood vessels in animals

  gas exchange surfaces are ventilated in animals
• How to prepare a slide on a light microscope


  drop of water to the middle of a clean slide

  use tweezers to peel off epidermal tissue place it on the slide

  drop of iodine solution used as stain

  place a cover slip at an angle
• How to use a light microscope

  Clip the slide onto the stage

  Select the lowest powered objective lens

  Coarse adjustment knobs to move stage down

  Fine adjustment knobs until clear image
• Sperm Cells 


  Specialised for reproduction

  Long tail and streamlined head

  Lots of mitochondria

  Carries enzymes
• Nerve Cells

  Specialised for rapid signalling

  Carries electrical signals

  Long to cover more distance

  Branched connections
• Muscle Cells


  Specialised for contraction

  Function to contract quickly

  Long to have space to contract

  Lots of mitochondria
• Muscle Cells


  Specialised for contraction

  Function to contract quickly

  Long to have space to contract

  Lots of mitochondria
• Restrictions of adult stem cells


  can only be specialised into certain types of cells
• Root Hair Cells


  Specialised for absorbing water and minerals

  On the surface of the plant roots

  Large surface area
• Osmosis


  The movement of water from a high to low concentration across a semi permeable membrane
• Active Transport


  Movement of particles from a low to high concentration

  Requires energy
• Differentiation


  the process by which a cell differentiates
• Eukaryotes


  Organisms made up of eukaryotic cells
• Prokaryote


  Single celled organism
• Magnification Equation


  Image size divided by actual size
• Stain Function


  Highlights structures in a cell by adding colour to them
• Diffusion


  The movement of a substance from a high to low concentration
• Substances that move through diffusion


  Oxygen

  Glucose

  Amino Acids

  Water
• binary fission occurs in prokaryotic cells
• correct conditions for bacteria

  warm environment

  lots of nutrients
• process of binary fission

  circular DNA and plasmids replicate

  cell gets bigger

  circular DNA strands move to opposite poles of the cell

  cytoplasm begins to divide and new cell wall starts to form

  cytoplasm divides

  2 daughter cells are produced
• if the environment of the bacteria becomes unfavourable, the bacteria will stop dividing and die