Science

• Magnification


  Size of image/real size of object
• Light microscopes


  • Cells range in size:

  animal cells are between 0.01 mm – 0.05 mm

  plant cells are between 0.01 mm – 0.10 mm

  The human eye can see objects as small as around 0.05 mm. A microscope is required to see cells in any detail.
• Compound microscope


  Uses two lenses to magnify the specimen – the eyepiece and an objective lens
• Magnification of the microscope

  Magnification of eyepiece × magnification of objective
• Magnification of a lens is shown by a multiplication sign followed by the amount the lens magnifies, eg ×10
• Most animal and plant cells are 0.01 – 0.10 mm in size. The smallest thing seen with the naked eye is about 0.05 mm.
• Micrometre


  Unit to measure most cells
• Nanometre


  Unit to measure sub-cellular structures and organisms like viruses
• Animal cells


  • Have a basic structure including cytoplasm, nucleus, cell membrane, mitochondria, ribosomes
• Plant cells


  • Have additional structures including chloroplast, cell wall, permanent vacuole
• Eukaryotic cells


  Cells of animals, plants and fungi
• Prokaryotic cells


  Cells of bacteria
• Sperm cell


  • Head contains genetic material, acrosome contains enzymes, middle piece has mitochondria, tail enables swimming
• Nerve cell


  • Extended with branches to communicate, covered in fatty sheath to insulate and speed up nerve impulses
• Muscle cell


  • Contains protein filaments that slide over each other to cause contraction, many mitochondria to provide energy
• Root hair cell


  • Large surface area to absorb water, thin walls to not restrict water movement
• Xylem cell


  • No top and bottom walls, thickened woody walls to support the plant
• Phloem


  • Transports dissolved sugars and amino acids both up and down the stem, companion cells provide energy