Biology

• Eukaryotic Cells

  Eukaryotic cells have a 'true' nucleus (containing DNA) and membrane - bound organelles (bits of the cell) .
• Prokaryotic Cells

  Prokaryotic cells have free floating DNA (no nucleus) and no membrane bound organelles.
• Cell membrane

  Controls movement of substances into and out of the cell
• Cell wall


  • Strengthens the cell
  • Supports the plant
• Cytoplasm


  • Jelly-like substance
  • Site of chemical reactions
• Nucleus


  • Contains genetic material (DNA)
  • Controls the activities of the cell
• Vacuole

  • Filled with cell sap
  • Keeps the cell turgid
• Chloroplasts

  • Contains chlorophyll
  • Site of photosynthesis
• Mitochondria

  Site of respiration (release of energy)
• Magnification:

  How much bigger and object appears to be than it really is when viewed through a microscope.
• Resolution:

  The smallest distance that can be seen between 2 points - the smaller the distance, the higher the resolving power.
• Magnification = size of image / real size of object
• Light microscope

  Device that uses visible light and a series of lenses to produce an enlarged image of an object
• Electron microscope

  Uses a beam of electrons instead of beams or rays of light. Living cells cannot be observed.
• Different Types of Microscopes

  • Light microscope
  • Electron microscope
• Positives of Electron Microscopes:

  Higher magnification

  Greater resolution

  Negatives:

  Expensive

  Specimens must be dead and viewed in a vacuum

  Black and white images
• Light Microscopes Positives:

  Within budget

  See colour images

  small / portable

  Specimen can be alive and unharmed

  Negatives:

  Lower magnification ( up to 2000x )

  Lower resolving power
• Sterile: Free from any microorganism
• Inocultion: Introducing microorganisms to a liquid or solid medium
• Aseptic: preventing infection / free from microorganisms
• Specialisation: Designed to perform a specific or particular role
• Specialised Cell: a cell that has a special shape and features that can help it to do its job
• Differentiation: The generration of specialised cells which acquire different organelles to enable them to carry out specific functions
• Stem cells: Cells that have not undergone variation
• Xylem: carries water and minerals
• Phloem: Transports glucose
• Sperm Cell Adaptations:

  Long tail to swim

  Enzymes in the head to help sperm get into the egg

  Lots of mitochondria to release lots of energy
• Root Hair Cell:

  Large surface area to absorb lots of water

  Thin cell wall to allow water to pass through easily

  No chloroplasts as they don't undergo photosynthesis
• Red Blood Cell:

  Large surface area

  Contains haemaglobin which picks up oxygen

  No nucleus, makes room for more oxygen

  Carries out oxygen from the lungs and carbon dioxide from the body back to the lungs
• Nerve Cells:

  Extremely elongated

  has many branches at ends to connect with other nerve cells

  The long axis (main branch) is covered in fat to prevent the electrical impulses affecting the surrounding parts of your body

  Carries out nerve impulses around your body
• Ciliated cell:

  Tiny hairs called cilia

  Stop lung damage

  hairs sweep mucus and dust and bacteria back up the throat to be swallowed

  If you smoke, the hairs die and mucus builds up -> smoker's cough
• Cell: smallest functional unit of an organsim. The basic unit of life
• DNA: polymer which has a double helix structure
• Genes: section of chromosome that codes for making poteins
• Chromosomes: hold the genes and is made of DNA. Humans have 46 total (23 pairs)