Cell biology

• Cells are studied using microscopes
• Microscopes


  • Let us see things that we cannot see with the naked eye
  • Have developed over the years in technology and knowledge
  • Improved lenses to form an image of a specimen
  • Use electrons instead of light to form an image
  • Have a higher resolution than light microscopes
  • Have a much higher magnification than light microscopes
• Resolution


  The ability to distinguish between two objects that are close together
• Using a microscope


  1. Select the objective lens

  2. Use the coarse adjustment knob to move the stage up and down

  3. Look down the eyepiece and use the fine adjustment knob to focus
• Stains can make subcellular structures easier to see
• Bacteria are prokaryotes and do not have a true nucleus or organelles like chloroplasts and mitochondria
• Eukaryotic cells are more complex and include animal and plant cells
• Subcellular structures in animal cells

  • Nucleus
  • Mitochondria
  • Cytoplasm
  • Cell membrane
  • Ribosomes
• Additional subcellular structures in plant cells

  • Rigid cell wall
  • Chloroplasts
  • Permanent vacuole
• Preparing a slide


  1. Add a drop to the middle of a clean slide

  2. Cut up an onion and separate out the epidermal tissue

  3. Place the epidermal tissue into the drop

  4. Add a drop of staining solution

  5. Place a cover slip over the specimen
• Magnification = image size / real size
• To write numbers in standard form, the first number needs to be between 1 and 10 and the power of 10 represents how many places the decimal point has moved
• Drawings of cells should be in proportion, have a title, magnification, and label the important features
• Cells Differentiate to Become Specialised
• Cell Differentiation


  The process by which a cell changes to become specialised for a specific function
• Cells that differentiate in multicellular animals are mainly used for packing and placing, such as skin or blood cells
• Stem cells are undifferentiated cells
• Sperm Cells


  • Have a long tail and streamlined head to help it swim to the egg
  • Have a lot of mitochondria to provide the energy needed
  • Carry enzymes in its head to digest through the egg cell membrane
• Nerve Cells


  • Are long to cover more distance
  • Have branched connections at their ends to connect to other nerve cells and form a network throughout the body
• Muscle Cells


  • Contract
• Root Hair Cells


  • Absorb water and minerals
• Embryonic Stem Cells


  Can turn into ANY type of cell
• Phloem and Xylem Cells


  • Transport substances such as food and water around plants
  • Are long and joined end to end to form tubes
• Stem cells may be able to cure many diseases
• Cells have the same basic bits but are specialised for their function
• Some people are against stem cell research
• Stem cells can produce identical plants
• Chromosomes


  Contain genetic information
• Cell Cycle


  Makes cells for growth, development and repair
• Cell Cycle


  1. Growth and DNA Replication

  2. Mitosis
• Mitosis produces two identical daughter cells
• Diffusion is the small random movement of particles from an area of higher concentration to an area of lower concentration
• Osmosis


  A special case of diffusion where water moves from an area of higher water concentration to an area of lower water concentration through a partially permeable membrane
• Cell Membranes


  • Allow some substances to pass through but not others
  • Only very small molecules can pass through freely
• The larger the surface area of the membrane


  The faster the diffusion rate
• Osmosis is the reason why it's bad to drink sea-water
• Root Hairs


  • Take in minerals using active transport
• Active Transport


  Uses energy to move substances against their concentration gradient
• Multicellular organisms need exchange surfaces
• Smaller objects have a larger surface area to volume ratio than larger objects