BIO KEY CONCEPTS

• Animal cell

  • Nucleus - stores genetic information
  • Cell membrane - controls what enters and exits
  • Mitochondria - responsible for respiration
  • Ribosomes - make essential proteins
  • Cytoplasm - where chemical reactions happen
• Plant cell

  • Cell wall - gives extra strength and protection
  • Vacuole - stores cell sap
  • Chloroplasts - for photosynthesis
• Bacteria cell

  • Flagellum - acts like a 'tail' for movement
  • DNA floats loose in cytoplasm
  • Plasmid loops - extra DNA
• Prokaryotic cells

  Smaller, simpler, no nucleus
• Eukaryotic cells

  Bigger, more complex, have a nucleus
• Sperm cell

  • Haploid nucleus
  • Lots of nutrients in cytoplasm
  • Acrosome with enzymes
  • Mitochondria for energy
  • Tail for movement
• Egg cell

  • Haploid nucleus
  • Lots of nutrients in cytoplasm
  • Can change membrane structure after fertilization
• Ciliated epithelial cell

  • Hair-like cilia to help move substances
• Light microscope


  Invented in 1500s, uses light beams, lower resolution, can view living cells
• Electron microscope

  Invented in 1930s, uses electron beams, higher resolution, cannot view living cells
• Total magnification

  Eyepiece lens magnification x Objective lens magnification
• Enzymes

  Biological catalysts made by living things, speed up reactions
• Substrate

  The thing the enzyme is reacting with
• Active site

  The place on the enzyme where the substrate fits
• Enzymes are highly specific, can only catalyze one reaction</b>
• Enzyme functions

  • Breakdown - larger molecules into smaller
  • Synthesis - smaller molecules into larger
• As temperature increases

  Enzyme activity increases until optimum, then quickly denatures
• As pH changes from optimum

  Enzyme begins to denature
• As substrate concentration increases

  Enzyme activity increases until all active sites are full
• Benedict's test for reducing sugars

  1. Add Benedict's reagent

  2. Heat gently

  3. Blue = low sugar, orange-red = high sugar
• Biuret test for proteins

  1. Add potassium hydroxide

  2. Add copper sulfate

  3. Purple colour indicates positive
• Emulsion test for lipids

  1. Add ethanol, shake, pour into water

  2. Milky water indicates positive
• Iodine test for starch

  1. Add iodine

  2. Blue-black colour indicates positive
• Calorimeter to measure food energy

  1. Set up apparatus

  2. Burn food under copper cup

  3. Measure temperature change

  4. Calculate energy using specific heat capacity
• Diffusion

  Passive movement of particles from high to low concentration
• Active transport

  Movement of particles from low to high concentration, requires energy
• Osmosis

  Diffusion of water molecules from high to low concentration through a partially permeable membrane
• Cells can be classified based on their structure and function into prokaryotic (bacterial) or eukaryotic (plant/animal).
• Iodine's test for starch

  1. Add iodine to test sample using pipette

  2. If starch present; brown/orange to blue blue/black
• Benedict's test for reducing sugars

  1. Add benedict's reagent to a food sample

  2. Place in 75C water bath

  3. If reducing sugars present, blue to coloured precipitate
• Emulsion test for lipids

  1. Shake the substance with ethanol until it disappears

  2. If lipids present; a white emulsion precipitates out
• Biuret's test for proteins

  1. Add biuret's reagent to food sample

  2. If proteins present, blue to purple
• Temp effect on enzyme activity

  1. Enzyme activity increases as the temperature goes towards the optimum

  2. When it surpasses this, the enzyme denatures, meaning the active site denatures, so no enzyme substrate complex is formed and so activity falls rapidly
• pH effect on enzyme activity

  1. Enzyme activity increases as the temperature goes towards the optimum pH

  2. Then, when the pH becomes more acidic or more alkaline, the activity falls as the active site denatures
• Both are similar descriptions
• All enzymes have similar optimum temperatures, but not all share the same optimum pH
• Calorimetry


  1. Weigh food using a balance

  2. Add water to boiling tube

  3. Measure water temperature

  4. Set fire to the food using a bunsen

  5. Keep burning food under boiling tube until it goes out

  6. Repeat this until it no longer sets fire

  7. Measure water temperature

  8. Use formula: energy in food = mass of water x temp change of the water x 4.2 to work out energy in food
• Osmosis

  The movement of water from a dilute to a concentrated solution through a partially permeable membrane
• To investigate osmosis in potatoes

  1. Prepare many sucrose solutions of different concentrations

  2. Peel and cut potato into different cylinders of the same size with a cork borer

  3. Divide cylinders into groups of three, and measure the mass of the group with a mass balance

  4. Place one group in each solution

  5. Leave these cylinders for around an hour

  6. Remove the cylinders and pat dry with a paper towel to remove excess

  7. Weigh the groups again, and record the percentage changes in mass
• Why cant antibiotics kill viruses

  Viruses have a thicker coating than bacteria