Cell Biology

• Microscopy Required Practical


  • Includes preparing a slide, using a light microscope, drawing any observations- use a pencil and label important observations
• Differentiation


  When a cell changes to become a specialised cell
• Specialised Cells and their Functions

  • Sperm - To get the male DNA to the female DNA
  • Nerve - To send electrical impulses around the body
  • Muscle - To contract quickly
  • Root hair - To absorb water from the soil
  • Phloem - Transports substances around the plant
  • Xylem - Transports water through the plant
• Osmosis and Potato Practical

  • Independent variable - concentration
  • Dependent variable - change in mass
  • Control variables - volume of solution, temperature, time, surface area of the potato
  • The potato in the sugar solution will lose water and so will have less mass at the end; the potato in the pure water solution will gain water
• Equations and Maths Skills

  • Conversions: Micrometres to millimetres (divide by 1000)
  • Standard Form: 0.003 = 3 x 10^-3, 5.6 x 10^-3 = 0.0056
• Prokaryotic and Eukaryotic Cells

  • Prokaryotic cells do not have a true nucleus, they have a single strand of DNA that floats in the cytoplasm
  • Bacterial cells contain plasmids
• Similarities and Differences between Animal and Plant Cells

  • Animal cells have: cell membrane, nucleus, cytoplasm, mitochondria, ribosomes
  • Plant cells have: cell membrane, nucleus, cytoplasm, chloroplasts, permanent vacuole, cell wall, mitochondria, ribosomes
• Chromosomes


  In the nucleus of a human cell there are 23 pairs of chromosomes, which contain a double helix of DNA and a large number of genes
• Cell Cycle


  The cell cycle makes new cells, DNA has to be copied/replicated before the cell carries out mitosis
• Mitosis


  The process where DNA is copied and the cell divides into two genetically identical daughter cells
• Types of Stem Cells

  • Embryonic stem cells - undifferentiated, can turn into any type of cell
  • Adult stem cells - found in bone marrow, can only turn into some types of cells e.g. blood cells
• Uses of Stem Cells

  • Replacing faulty blood cells
  • Making insulin producing cells
  • Making nerve cells
• Arguments for and against stem cell research

  • For - Curing patients with stem cells more important than rights of embryos, using unwanted embryos from fertility clinics
  • Against - Embryos are human life, scientists should find other sources of stem cells
• Stem Cells in Plants

  Found in the meristem, able to produce clones of the plant, can be used to grow crops with specific features
• Gas Exchange in Lungs

  • Alveoli have a large surface area, moist lining, thin walls and good blood supply
• Gas Exchange in Small Intestine

  • Villi increase the surface area to absorb more digested food, they are a single layer of cells with good blood supply
• Gas Exchange in Plants

  • Leaf surface is flattened to increase surface area for gas exchange by diffusion, oxygen and water vapour diffuse out of the stomata which are opened and closed by guard cells
• Diffusion


  The movement of particles from an area of high concentration to an area of lower concentration
• Cell Membranes


  Only small molecules can get through, larger molecules require active transport
• Osmosis


  The movement of water molecules across a partially permeable membrane from an area of high water concentration to an area of low water concentration
• Active Transport


  The movement of substances against a concentration gradient, requiring energy
• Gas Exchange in Fish

  • Water enters through the mouth and flows over the gill filaments, carbon dioxide diffuses from the blood to the water, the large surface area and thin walls of the gill lamellae allow efficient gas exchange