Biology Topic 1

• How can we see cells?

  Via microscopes (normal & electron)
• What are the differences between the 2 microscopes?

  Light is cheaper to make however it shows the outlines of cells whereas electron is expensive but can visualise sub-cellular structures due to their high resolution and power.
• Formula for magnification?


  Magnification = Image height / Object height
• Measurement for cells and conversion

  Cells are measured in μm and can be converted to mm via by 1000
• What are the two groups of cells?

  Prokaryotic/bacteria cell (no nucleus) and eukaryotic/plant/animal cell(contains a nucleus) cells.
• Organelles

  • Cell membrane (found in both) semi permeable, controls what enters & leaves.
  • Cell wall (plant cell ONLY) made from cellulose providing a rigid structure.
  • Cytoplasm (both) liquid in which most chemical reactions take place.
  • Mitochondria (both) where respiration takes place releasing energy for the cell
  • Ribosomes (both) where proteins are assembled/ protein synthesis
  • Chloroplasts (plant cell ONLY) contains chlorophyll for photosynthesis.
• What do bacteria reproduce by and how often?

  Binary fission, rapidly and every 10 minutes
• How many pairs of chromosomes do all human cells have?

  23 (diploid)
• How are new diploid (new) cells made?

  Mitosis, for growth and repair.
• What is the process of mitosis?

  • Nucleus dissolves & genetic material is duplicated.
  • Two sets of chromosomes move to different sides.
  • Organelles are duplicated
  • Cell divides producing two genetically identical diploid cells
• What are examples of specialised cells?

  Nerve, muscle, root hair, xylem and phloem
• What are stem cells?

  Cells that haven't been specialised yet to perform specific functions. They're found in human/animal embryos and meristems in plants.
• Where else can stem cells be made but what only into?

  Bone marrow, but can only be specialised into red blood cells.
• What are embryo clones?

  Genetically identical copies of an embryo which can be harvested for stem cells to treat conditions without them being rejected by the patient's body.
• What can cloning be used for?

  Prevent species from becoming extinct or produce crops with desired traits.
• What is diffusion?

  Diffusion is the movement of particles from an area of high concentration to an area of low concentration.
• What is osmosis?

  Osmosis is the diffusion of water (high to low conc.) through a semi-permeable membrane
• What factors affect osmosis and diffusion?

  Temperature, surface area & concentration gradient.
• What is active transport?

  Movement of nutrients and minerals through a membrane.