Biology - cells

• Plant cell - sub-cellular structures

  • cell wall
  • cell membrane
  • permanent vacuole
  • mitochondria
  • ribosomes
  • cytoplasm
  • chloroplasts
• Animal cell - sub-cellular structures

  • cell membrane
  • cytoplasm
  • mitochondria
  • ribosomes
• Bacteria cell - sub-cellular structures

  • cell wall
  • cell membrane
  • plasmids
  • nucleiod
  • cytoplasm
  • flagellum
  • ribosomes
• Prokaryotic cells

  • Example - bacteria cell
  • Genetic material is enclosed in a single strand of DNA (nucleoid) and sometimes plasmids which are small rings of DNA that are found in the cytoplasm
  • cells divide by binary fission
  • binary fission is the process by which prokaryotic cells, such as bacteria, divide and reproduce.
  • The speed of this division depends on conditions such as temperature and nutrient concentrations.

  
• Eukaryotic cells

  • Example - animal and plant cells
  • genetic material is enclosed in a nucleus
  • cells divide by mitosis
  • mitosis is the process by which eukaryotic cells, such as animal and plant cells, divide and reproduce
  • the speed of this division is dependant on the temperature and even light (plant cell)
• Nucleus

  • controls the cell’s activities
  • contains genetic material (DNA)
• Cytoplasm

  • A jelly-like substance that contains nutrients, salts and organelles (e.g ribosomes)
  • where chemical reactions take place
• Cell wall

  • Made from cellulose
  • strengthens the cell
• Cell membrane

  • Controls the movement of substances in and out of the cell
  • this is because its structure is permeable to some structures and not to others
• Mitochondria

  • Site of aerobic respiration
  • therefore, releases energy for the cell to use for its function
• Ribosomes

  • site of protein synthesis
  • where proteins are made
• Permanent vacuole

  • supports the cell and maintains its shape (keeps the cell turgid)
  • contains cell sap
• Chloroplasts

  • the site of photosynthesis
  • contains chlorophyll
  • chlorophyll is a green pigment that absorbs sunlight for photosynthesis. therefore, making glucose to provide the cells with energy to grow and respire
• Nucleoid

  • Single strand of DNA found in the cytoplasm of a prokaryotic cell (e.g bacteria cell)
• Plasmids

  • small rings of DNA
• Order of magnitude

  
• Microscopy - Practical 1: Preparing the slide - plant cells

  Preparing the slide - plant cells

  • cut a thin layer of epidermal cells from inside an onion
  • place cells on a microscope slide
  • add a drop of iodine to dye the cell structures
  • lower cover slip onto the onion cells using forceps - this needs to be done gently to avoid trapping air bubbles
• Microscopy - Practical 1: Preparing the slide - animal cells

  • Remove cells from the inside of your cheek using a cotton bud
  • Smear the cotton bud onto a microscope slide
  • Add a drop of methylene blue (a chemical stain)
  • Lower a coverslip onto the cheek cells using forceps - this needs to be done gently to prevent trapping air bubbles
• Microscopy - Practical 1

  1. Place slide on to the stage and use the clips to hold the slides in place

  2. Select the lowest power objective lens (x4)

  3. Slowly turn the coarse focusing dial to position the objective lens so it is almost touching the microscope slide - look at the microscope from the side when doing this because if we look through the eyepiece when doing this, we could damage the damage the slide

  4. Use a higher power objective lens (x10 or x40)

  5. Look down the eyepiece lens and slowly turn the coarse focusing dial to increase the distance between the objective lens and the slide - do this until the cells come into focus

  6. Use the fine focusing dial to bring the cells into a clear focus

  7. Calculate the total magnification
• Total magnification

  Magnification of eyepiece lens x magnification of the objective lens