B1 - cell biology

• Organisms can be prokaryotic or eukaryotic
• Animal and plant cells are eukaryotic
• Bacteria is a prokaryotic cell
• Nucleus contains genetic material that controls activities of cell
• Cytoplasm is where chemical reactions take place - contains enzymes
• Cell membrane - holds cell together and controls what goes in and out
• Mitochondria is where aerobic respiration takes place , transfer energy
• Ribosome is where proteins Are made
• Animal cell contains

  nucleus

  cytoplasm

  cell membrane

  mitochondria

  ribosome
• Plant cells contain

  nucleus

  cytoplasm

  cell membrane

  mitochondria

  ribosome

  cell wall

  permanent vacuole

  chloroplast
• Cell wall - supports and strengthens cell
• Permanent vacuole - contains cell Sap - weak solution of sugars and salts
• Chloroplast - where photosynthesis occurs , they contain Chlorophyll which Absorbs light needed for photosynthesis
• Bacteria cells contain

  cell membrane

  cell wall

  cytoplasm
• bacteria Cells don’t have true nucleus instead have a single circular strand of DNA that floats freely in the cytoplasm
• Bacteria cells contain plasmids - small rings of DNA
• Bacteria don’t have chloroplasts or mitochondria
• Two types of microscopes - light and electron microscopes
• Electron microscopes use electrons instead of light to form an image they have A higher magnification
• Electron microscopes have higher magnifications and higher resolution -
• resolution is the ability to distinguish between two points so higher resolution gives a sharper image
• Electron microscopes let us see smaller things in more detail like internal structures - mitochondria and chloroplasts and tinier - ribosome and plasmids
• Microscopes let us see things we can’t see with naked eye , microscopy techniques- developed
• Light microscopes use light and lenses to form an image and magnify it , let us see individual cells and larger subcellular Structures like nuclei
• Magnification - size of image divide by charge of real object
• How to prepare a slide steps

  1)add drop of water to middle of clean slide

  2) cut up an onion and separate into layers using tweezers peel of epidermal tissue

  3) use tweezers place epidermal tissue into water on slide

  4) add drop of iodine solution - is a stain , stains used to highlight objects in a cell - adds colour

  5)place a cover slip on top , stand coverslip upright on slide , next to water , then tilt and lower it , try not to get any air bubbles , they obstruct your view
• Light microscope -

  1)clip slide you prepared on stage

  2)select lowest powered objective lens

  3) use the coarse adjustment knob to move stage up to just below objective lense

  4)look down eyepiece , use coarse adjustment knob to move stage downwards until image roughly focus

  5) adjust focus with fine adjustment knob until clear image

  6) if need greater magnification , swap to higher powered objective lense
• cells differentiate to become specialised
• Differentiation is the process which a cell changes to become specialised for its job
• As cells change they develop different sub cellular structures and turn into different types of cells this allows them to carry out specific functions
• Most differentiation occurs as an organism develops
• In animal cells the ability to differentiate is lost at an early stage after become specialised
• Lots plants cells don’t ever lose ability to differentiate
• The cells that differentiate in mature animals are mainly used for repairing and replacing cells
• Stem cells are undifferentiated cells
• Sperm cells are specialised for reproduction
• Function of a sleek is to get male DNA to female DNA

  it has a long tail and streamlined head to help it swim to egg
• Sperm cell features

  long tail , streamlined head -swim

  lots mitochondria - provide energy needed

  carries enzymes in its head to digest through egg cell Membrane
• Nerve cells are specialised for rapid signalling
• Function of nerve cells is to carry electrical signals around Body