Cell biology

• Eukaryotic


  Organisms made of eukaryotic cells
• Prokaryotic


  Single-celled organisms with prokaryotic cells
• Eukaryotic cells


  • Contain a nucleus
  • Contain membrane-bound organelles
• Prokaryotic cells


  • No nucleus
  • Single circular strand of DNA
  • May have plasmids
• Parts of a cell

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Cell wall (in plants)
• Microscopes


  • Use electrons to form an image
  • Provide higher magnification and resolution
• Nucleus


  Contains genetic material and controls cell activity
• Cytoplasm


  • Gel-like substance where most chemical reactions happen
  • Contains enzymes
• Preparing a slide


  1. Add a drop of water

  2. Cut up onion and peel off epidermal tissue

  3. Place tissue on slide

  4. Add iodine stain

  5. Cover with coverslip
• Cell wall


  • Made of cellulose
  • Supports and strengthens the cell
• Cell sap


  Weak solution of sugars and salts
• Chloroplasts


  • Where photosynthesis occurs
  • Contain chlorophyll to absorb light
• Bacterial cells


  • No nucleus
  • Single circular strand of DNA
  • May have plasmids
• Nerve cells


  Rapid signalling to carry electrical signals
• Muscle cells


  Contraction to generate energy
• Sperm cells


  • Specialised for reproduction
  • Long tail and streamlined head
  • Contain enzymes to digest through egg
• Root hair cells


  Absorb water and minerals
• Phloem and xylem cells


  Transport food and water around plants
• Stem cells


  Undifferentiated cells that can differentiate into different cell types
• Chromosomes contain genetic information
• Diffusion


  Movement of particles from high to low concentration
• Osmosis


  Movement of water molecules across a partially permeable membrane
• Cell cycle


  1. Growth

  2. DNA replication

  3. Mitosis to produce two identical cells
• Larger surface area of membrane

  Faster diffusion rate
• Higher temperature


  Faster diffusion rate
• Larger concentration gradient


  Faster diffusion rate
• Most body cells have two copies of each chromosome, one from each parent
• Body cells have 23 pairs of chromosomes
• Stem cells can differentiate into different cell types
• Active transport moves substances against a concentration gradient
• For farmers


  • Disease resistance
• Identical plants that have desired
• Diffusion


  The movement of particles from an area of high concentration to an area of low concentration
• Happens in liquids and gases because particles are free to move
• Bigger concentration gradient


  Faster diffusion rate
• Higher temp


  Faster diffusion rate
• Larger surface area of membrane

  Faster diffusion rate
• Osmosis


  The movement of water molecules across a partially permeable membrane from an area of higher concentration to an area of lower concentration
• Partially permeable membrane


  Has very small holes in it
• Required Practical


  1. Cut up a potato into identical cylinders

  2. Measure the mass of the potato cylinders and place them in beakers with different sugar solutions for 24 hours

  3. Take them out, dry them and measure the mass again