Key Concepts in Biology

• 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


  • Ribosomes
  • Cell membrane
  • Cytoplasm
  • Flagellum - acts like a 'tail'
  • DNA floats loose in cytoplasm
  • Plasmid loops - extra DNA
• Prokaryotic cells


  Smaller, simpler, no nucleus
• Eukaryotic cells


  Bigger, more complex, have a nucleus
• Cell differentiation


  Cells switch particular genes on/off to develop specialized characteristics
• Sperm cell


  • Haploid nucleus
  • Lots of nutrients in cytoplasm
  • Acrosome - enzymes to break down egg
  • Mitochondria - provide energy
  • Tail for movement
• Egg cell


  • Haploid nucleus
  • Lots of nutrients in cytoplasm
  • Can change structure to stop more sperm entering
• Light microscope


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


  Invented in 1930s, uses beams of electrons, much higher resolution, cannot view living cells
• Finding total magnification


  Multiply eyepiece lens magnification by objective lens magnification
• Calculating magnification


  Divide image size by real size
• Enzymes


  Biological catalysts made by living things, speed up reactions
• Enzyme structure


  • Enzyme molecule
  • Substrate - thing the enzyme reacts with
  • Active site - where substrate fits
• Enzyme specificity


  Enzymes can only catalyze one reaction, one type of substrate can fit
• Enzyme functions


  1. Breakdown - larger molecules into smaller

  2. Synthesis - smaller molecules into larger
• Enzyme optimum conditions


  • Temperature too low - not enough energy
  • Temperature too high - enzyme denatures
  • pH off optimum - enzyme denatures
  • Increasing substrate concentration - increases activity until active sites full
• Benedict's test


  1. Add Benedict's reagent, heat gently

  2. Blue - low sugar, Orange-red - high sugar
• Biuret test


  1. Add potassium hydroxide, add copper sulfate

  2. Purple if positive for proteins
• Emulsion test


  1. Add ethanol, shake, pour into water

  2. Milky if positive for lipids
• Iodine test


  1. Add iodine

  2. Blue-black if positive for starch
• Diffusion


  Movement of particles from high to low concentration, passive process
• Active transport


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


  Movement of water molecules from high to low concentration through partially permeable membrane