Alevel biology

• How does TEM microscope works

  Use electromagnets to focus a beam of electrons

  Beam transmitted through specimen

  Denser part absorbs more electrons

  (seen as more darker )
• Advantages of TEM microscope 


  Higher resolution image - give more detailed image

  Allow internal structures within cell to be seen
• Disadvantages of TEM microscope 


  Only used on thin specimen

  No colour image

  No 3D image

  specimen is not living
• What is an SEM microscope 


  Uses beam of electron across specimen

  Specimen bounces of beams electrons are detected

  which allows a 3D image to be produced
• Advantages of SEM microscope


  Used on thick specimen

  Gives a 3d image
• Disadvantages of SEM microscope 


  No colour image

  Not used on love specimen

  Low resolution image
• Light microscope 


  Uses a beam of light to form image which limits resolution

  Smaller organelles are not seen
• electron microscope 


  use beam of electron to form an image which increases resolution

  smaller organelles able to be seen
• What happens during interphase 


  G1- cell elongates and new organelles and proteins are made

  s- dna is replicated

  G2- cell continues elongation and proteins need for cell division are made
• What happens during prophase 


  Chromatone condense into chromosomes

  Nuclear membrane starts to break down

  Centrioles migrating to poles spindle fibres developing
• What happens in metaphase 


  Chromosomes viable as 2 chromatids

  Align down equator of cell
• What happens in anaphase 


  Spindle fibres shorten

  Centrometest split

  Chrimatids move to opposite poles
• What happens in telophase 


  Chromosomes start to uncoil

  Nuclear membrane start to reform
• What happpens in cytokinesis 


  Cell splits into two forming two genetically identical daughte cells