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• Cells


  The basic units of life that make up all living organisms
• Eukaryotic cells


  • Complex
  • All animal and plant cells are eukaryotic
• Prokaryotic cells


  • Smaller and simpler
  • Bacteria are prokaryotic cells
• Cells contain subcellular structures - parts of cells that each have specific functions
• Structures within eukaryotic cells

  • Nucleus
  • Cell membrane
  • Cytoplasm
  • Ribosomes
  • Mitochondria
• Additional structures in plant cells

  • Cell wall
  • Chloroplasts
• Structures within prokaryotic cells

  • Chromosomal DNA
  • Plasmids
  • Cell membrane
• Microscopes


  Instruments that use lenses to magnify and increase the resolution of objects
• Light microscopes


  • Can see cell nucleus and chloroplasts
• Electron microscopes


  • Have higher magnification and resolution than light microscopes
  • Can see smaller subcellular structures like plasmids
• Calculating total magnification


  Eyepiece lens magnification x Objective lens magnification
• Calculating magnification from image and real size


  Magnification = Image size / Real size
• Standard form


  A way to write very big or very small numbers in a simpler way
• Preparing a specimen for light microscopy

  1. Take thin slice

  2. Add drop of water

  3. Add specimen

  4. Add stain if needed

  5. Lower cover slip
• Viewing a specimen under a light microscope

  1. Clip slide onto stage

  2. Use lowest power objective lens

  3. Move stage up until in focus

  4. Adjust fine focus

  5. Use higher power lens if needed
• High magnification isn't always best as you may not see the whole specimen and it can be difficult to focus
• DNA


  The chemical instructions that tell the body which proteins to make
• DNA structure


  • Double helix
  • Made of nucleotides
  • Bases join between strands
• Monomers


  Small, basic molecules
• Polymers


  Large, complex molecules made from chains of monomers
• DNA is a polymer made up of nucleotide monomers
• Enzymes


  • Control cell reactions
  • Have active sites that are substrate specific
• Temperature increases


  Enzyme activity increases at first
• Temperature gets too high


  Enzyme is denatured and can't catalyse reaction
• Optimum temperature


  The temperature at which an enzyme works best
• pH is too high or too low


  Enzyme is denatured
• Optimum pH


  The pH at which an enzyme works best
• Substrate concentration increases


  Reaction rate increases
• Enzyme concentration increases


  Reaction rate increases
• Investigating effect of temperature on enzyme activity

  1. Measure oxygen produced by catalase enzyme

  2. Repeat at different temperatures
• Controlling variables is important to make the investigation fair
• Investigating how fast a product appears

  1. Collect oxygen produced

  2. Measure how much oxygen is produced in a set time

  3. Add hydrogen peroxide to a boiling tube

  4. Put tube in water bath at 10°C

  5. Add a source of catalase

  6. Record oxygen produced in first minute

  7. Repeat at 20°C, 30°C, 40°C

  8. Control variables
• Investigating how fast a substrate disappears

  1. Put a drop of iodine solution into each well

  2. Every 10 seconds, drop a sample of the mixture into a well

  3. Record time when iodine solution remains browny-orange

  4. Repeat at different temperatures

  5. Control variables
• Respiration


  The process of transferring energy from glucose (or other biological molecules)
• Respiration is NOT "Breathing In and Out"
• Respiration


  • It's a chemical process that goes on in the cells of all living organisms
  • The energy released by respiration is used to make ATP
  • Respiration is an exothermic reaction - some energy is released as heat
• Substrates that can be broken down in respiration

  • Glucose
  • Other carbohydrates
  • Fats
  • Lipids
• Aerobic respiration


  Respiration with oxygen
• Aerobic respiration


  • Produces lots of ATP - 32 molecules per molecule of glucose
  • The equation is: glucose + oxygen → carbon dioxide + water
• Anaerobic respiration


  Respiration without oxygen