1. Cell biology

• Eukaryotic cells contain a nucleus
• Plant and animal cells have the following:

  Cytoplasm - chemical reaction take place

  Cell membrane - controls what enters and leaves the cell

  Mitochondria - to release energy during respiration

  Ribosomes - site of protein synthesis
• Plant cells have 3 extra characteristics:

  Cell wall - made of cellulose, to strengthen and keep cell shape

  Chloroplast - the site of photosynthesis

  Permanent vacuole - filled with cell sap, keeps the cell dense
• Prokaryotic cells - no nuclei, single DNA loop

  Cell wall

  Cell membrane

  Ribosomes

  Cytoplasm

  Flagella

  Genetic material
• Specialised cells - cells that have a specific function and are adapted to carry out that function.
• Nerve - carries electrical signals
• Sperm - fertilises egg

  streamlined to swim faster

  long tail to swim
• Muscle - they contact to allow movement

  Contains large number of mitochondria
• Red blood cell - transports oxygen

  Contains haemoglobin to bind to oxygen

  Has no nucleus

  Increases surface area
• Root hair cell - absorb water and minerals from soil

  hair like projections to increase surface area
• Xylem - carry water and minerals from the roots to the leaves.

  Transpiration - dead cells

  Flows in ONE direction
• Phloem - carry glucose

  Translocation - living cells have end plates and holes

  Flows in BOTH directions
• Light microscope - uses light rays
• light microscope - max magnification x1500
• Light microscope - resolution 200nm
• Light microscope - small and portable
• Light microscope - low cost
• Light microscope

  Pros - can observe living organisms

  Cons - low resolution
• Electron microscope - uses electron beams
• Electron microscope - max magnification 2,000,000x
• Electron microscope - resolution, 0.2nm
• Electron microscope - very large and not portable
• Electron microscope - cost a lot
• Electron microscope

  Pros - high detailed/ high resolution, 2D and 3D images

  Cons - cannot view living specimens
• Magnification = image size/actual size
• Stem cell - undifferentiated cells that can differentiate to form specialised cells
• Stem cells from embryos can be used to treat patients with certain diseases.
• We can use stem cells to make different types of human cells. Called therapeutic cloning
• Adult stem cells can form many types of cells, including blood cells
• Stem cells in plants are found in the meristem tissue, which is found in the tips of shoots and roots
• Meristem tissue can be used to clone plants with useful features e.g. disease resistance
• Mitosis divides into 2 identical daughter cells
• Mitosis

  1. The cell grows. The DNA replicates to form two copies of each chromosomes. NEW mitochondria and ribosomes are made
  2. Mitosis; one set of chromosomes is pulled to each end of the cell. The nucleus divides
  3. The cytoplasm and cell membrane divide. 2 new identical cells are formed
• Mitosis - for growth and repair of damaged cells, and for cell division during development
• Cancer is the result of uncontrolled cell division and causes mutations in the cell
• Benign tumours are uncontrolled growths of abnormal cells. Contained area. Non-cancerous and don't invade other parts of the body
• Malignant tumours are cancerous and can spread to other parts of the body
• Diffusion - movement of particles from high to low concentration, down a concentration gradient
• Factors that affect the rate diffusion

  • The bigger the difference in concentrations, the faster diffusion
  • The higher the temperature, the faster diffusion
  • The bigger the surface area area of the membrane, the faster diffusion
• Osmosis - diffusion of water through a partially permeable membrane from a region of higher water concentration to a region of lower water concentration