biology

• What are the main organelles found in a cell?

  Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes, chloroplasts (in plant cells)
• What is the key difference between prokaryotic and eukaryotic cells?

  Prokaryotic cells lack membrane-bound organelles and a true nucleus, while eukaryotic cells have membrane-bound organelles and a nucleus.
• What is cell specialization?

  The process by which cells develop specific structures and functions to perform particular roles in the body.
• What is cell differentiation?


  The process by which a less specialized cell becomes a more specialized cell type.
• What type of transport requires energy in the form of ATP?

  Active transport
• What is the difference between diffusion and osmosis?

  Diffusion is the movement of particles from high to low concentration, while osmosis is the diffusion of water molecules across a partially permeable membrane.
• Drawbacks of using embryonic stem cells

  • Limited supply of embryonic stem cells
  • Ethical issues
  • Body may reject these cells
  • Medication cannot always stop rejection
  • Possible virus transmission
  • Possible tumor development
  • Embryos have potential for human life
• An alternative to using embryonic stem cells is using adult stem cells from the patient
• Using adult stem cells can prevent rejection but can only work when blood cells are needed
• Specialised cells


  Have a specific role within the organism and are adapted to fulfil that role
• Specialised cells have specific amounts of different organelles to be the most efficient at their role
• Stem cells in medicine

  1. Embryo cells are extracted from early embryos

  2. They are then grown in a laboratory

  3. They are simulated to differentiate into the specific cell needed

  4. They are given to patients to replace faulty cells
• Conditions caused by faulty cells

  • Type 1 diabetes
  • Paralysis
  • Sickle cell anaemia
• Types of stem cells

  • Embryonic stem cells
  • Adult stem cells
  • Plant stem cells
• Stem cells


  Are able to divide by mitosis to form more cells which can then differentiate into specialised cells
• Adult stem cells can divide by mitosis but are only able to differentiate into platelets, white blood cells, and red blood cells
• Adult stem cells replace damaged cells but do not form any new tissue
• Plant stem cells are found in meristems which are areas that are always growing
• Plant stem cells persist for the plant's entire life
• Binary fission


  Asexual reproduction of prokaryotic organisms (mostly bacteria) to create more cells
• Binary fission process


  1. Before a bacteria can divide, it grows in size and replicates its genetic material

  2. Genetic strands move to either end of the cell

  3. Plasmids are arranged randomly

  4. A new cell wall grows down the middle of the cell

  5. The two sides of the cell pull apart

  6. Two daughter cells are created
• All living organisms require a continuous supply of new cells for growth, development, and repairing damaged cells
• Mitosis process


  1. Cells increase in size

  2. The number of sub cellular structures increase

  3. DNA is replicated so that each new cell has a full set

  4. Each chromosome is duplicated

  5. Chromosomes are pulled to each end of the cell

  6. Cell membrane and cytoplasm pull apart forming two daughter cells which are identical to each other and the parent cell
• How to prepare a slide to view onion cells

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

  2. Cut up an onion and separate it into layers

  3. Use tweezers to peel off some epidermal tissue

  4. Place the epidermal tissue into the water on the slide

  5. Add a drop of iodine solution

  6. Place a cover slip on top
• Slide


  A strip of clear glass or plastic onto which the specimen is mounted
• Iodine solution is a stain
• Stains


  Used to highlight objects in a cell by adding colour to them
• Using the microscope

  1. Clip prepared slide to stage

  2. Select lowest-powered objective lens

  3. Use course adjustment knob to move stage just below lens

  4. Look down eyepiece and move stage down until roughly in focus

  5. Use fine adjustment knob to fully focus

  6. Look with higher magnification
• Image size = actual size x magnification
• 1mm = 1000 μm