Topic 1

• Eukaryotic cells


  Animal and plant cells
• Prokaryotic cells


  Bacterial cells
• Structures in eukaryotic cells


  • Cell membrane
  • Cytoplasm
  • Nucleus containing DNA
• Structures in prokaryotic cells


  • Cell wall
  • Cell membrane
  • Cytoplasm
  • Single circular strand of DNA and plasmids
• Organelles in animal and plant cells


  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Organelles only in plant cells


  • Chloroplasts
  • Permanent vacuole
  • Cell wall
• Structures in bacterial cells


  • Cytoplasm
  • Cell membrane
  • Cell wall
  • Chromosomal DNA (circular)
  • Plasmids
  • Flagella
• Differentiation


  A process that involves the cell gaining new sub-cellular structures in order for it to be suited to its role
• Specialised animal cells


  • Sperm cells
  • Egg cells
  • Ciliated epithelial cells
• Specialised plant cells


  • Root hair cells
  • Xylem cells
  • Phloem cells
• Light microscope


  Has two lenses, usually illuminated from underneath, maximum magnification of 2000x and resolving power of 200nm
• Electron microscope


  Uses electrons instead of light, can achieve magnification up to 2,000,000x and resolving power of 10nm (SEM) and 0.2nm (TEM)
• Electron microscopes have allowed the discovery of viruses and detailed examination of proteins
• Magnification


  Magnification of the eyepiece lens x magnification of the objective lens
• Size of an object

  Size of image/magnification = size of object
• Prefixes


  • Centi (0.01)
  • Milli (0.001)
  • Micro (0.000,001)
  • Nano (0.000,000,001)
• Estimating population size


  Take a sample area, count the number of organisms, then multiply by the number of sample areas in the whole field
• Parts of a light microscope


  • Eyepiece
  • Barrel
  • Turret
  • Lens
  • Stage
• Using a light microscope


  1. Place slide on stage

  2. Turn focus wheel to obtain clear image

  3. Start with lowest objective lens magnification

  4. Increase magnification and refocus
• Preparing a slide


  1. Take thin layer of cells

  2. Add chemical stain

  3. Apply cells to glass slide

  4. Lower coverslip
• Magnification calculations


  • Magnification = measured size / actual size
  • Actual size = measured size / magnification
  • Total magnification = objective lens magnification x eyepiece lens magnification
• Enzymes


  Biological catalysts that increase the rate of reaction without being used up
• Active site


  The uniquely shaped site on an enzyme where the substrate binds
• Lock and key hypothesis

  The shape of the substrate is complementary to the shape of the active site, forming an enzyme-substrate complex
• Magnification

  Measured size / actual size
• Actual size


  Measured size / magnification
• Total magnification


  Objective lens magnification x eyepiece lens magnification
• Enzymes


  Biological catalysts (a substance that increases the rate of reaction without being used up)
• Enzymes


  • Present in many reactions - allowing them to be controlled
  • They can both break up large molecules and join small ones
  • They are protein molecules and the shape of the enzyme is vital to its function
• Active site


  Where the substrate binds
• Lock and Key Hypothesis


  1. The shape of the substrate is complementary to the shape of the active site (matches the shape of the active site), so when they bond it forms an enzyme-substrate complex

  2. Once bound, the reaction takes place and the products are released from the surface of the enzyme
• Enzymes can only catalyse (speed up) reactions when they bind to a substrate that has a complementary shape, as this is the only way that the substrate will fit into the active site
• Enzyme specificity


  Enzymes can only catalyse reactions when they bind to a substrate that has a complementary shape
• Enzymes


  • They require an optimum pH and temperature, and an optimum substrate concentration
• Optimum temperature


  In humans is a range around 37 degrees Celsius (body temperature)
• As temperature increases


  The rate of reaction increases up to the optimum, then rapidly decreases and eventually the reaction stops
• Denaturation


  When the bonds that hold the enzyme together break, changing the shape of the active site so the substrate can no longer 'fit into' the enzyme
• Optimum pH


  For most enzymes is 7 (neutral), but some have a lower optimum pH
• If the pH is too high or too low


  The forces that hold the amino acid chains that make up the protein will be affected, changing the shape of the active site so the substrate can no longer fit in
• Substrate concentration


  The concentration of the substance binding to the enzyme