Biology

• Cells


  • Animal Cells are eukaryotic (contain a nucleus)
  • Divide by mitosis
• Animal Cell Organelle Name

  • Cytoplasm
  • Nucleus
  • Ribosome
  • Mitochondria
  • Cell Membrane
• Cytoplasm


  Jelly-like structure where all chemical reactions in the cell take place
• Nucleus


  Contains genetic material and controls the cell's activities
• Ribosome


  Where protein synthesis occurs
• Mitochondria


  Contains enzymes for respiration and where most energy is released during respiration
• Cell Membrane


  Controls what enters and leave the cell
• Plant

  • Divide by mitosis
  • Eukaryotic and share a lot of the same organelles as animal cells but also has three unique organelles
• Plant Cell Organelle Name

  • Cell Wall
  • Chloroplasts
  • Permanent Vacuole
• Cell Wall


  Keeps cell rigid
• Chloroplasts


  Carries chlorophyll which is responsible for photosynthesis + also contains enzymes for photosynthesis
• Permanent Vacuole


  Filled with cell sap to keep cell swollen
• Bacterial Cells


  • Prokaryotic (smaller and simpler)
  • Divide by Binary Fission
• Organelle Name


  • Chromosomal DNA
  • Cell Wall
  • Flagellum
  • Plasmid DNA
• Chromosomal DNA


  Controls cell's activity and replication (not in a nucleus/ floats free in cytoplasm)
• Cell Wall


  Provides structure and protection
• Flagellum


  Movement (Moves cell away from threats towards beneficial substances)
• Plasmid DNA


  Contain genes for things like drug resistance and can be passed round other bacterium
• Sperm Cell


  • Tail enables sperm to swim
  • Midpiece containing Mitochondria provide sperm with energy to swim and fertilise egg
  • Haploid Nucleus carries genetic material for fertilisation
  • Acrosome contains enzymes to penetrate egg
• Egg Cell


  • Cell Membrane changes structure after fertilisation to prevent more sperm from entering
  • Mitochondria provides cell with energy for fertilisation
  • Cytoplasm contains nutrients for growth of the early embryo
  • Haploid Nucleus contains genetic material for fertilisation
• Ciliated Epithelial Cell


  Cilia move substances up the trachea (mucus) so it doesn't reach the lungs
• Light Microscopes


  • Used to study living cells
  • Pass light through the specimen
  • Magnification = Size of Image / Real Size of Object
  • Let us see nuclei and chloroplasts
• Electron Microscopes


  • Use beams of electrons instead of light
  • Have a higher magnification and resolution than light microscopes
  • TEM - Transmission Electron Microscope - Used to examine thin slices or sections of cells and tissue
  • SEM - Scanning electron Microscope - Used to examine surface structure of specimens
• Numbers


  • milli (10−3) 0.001
  • micro (10−6) 0.000001
  • nano (10−9) 0.000000001
  • pico (10−12) 0.000000000001
• Enzymes


  • Biological enzymes that speed up useful chemical reactions in the body
  • Lock and Key Mechanism - Enzymes have active sites for smaller substrates to fit into, each active site has a different shape matching to a specific substrate - Highly specific
• Denaturing Enzymes


  • If exposed to high temperatures or pHs, active sites may change in shape. This means the key doesn't fit into the lock - The enzyme is denatured
  • As temperature increases so does rate of enzyme activity. But after some point, it changes the active site's shape
  • pH also alters the shape of an enzyme's active site. Optimum pH for enzymes depends on their location
• Enzyme activity


  As substrate concentration increases so does enzyme activity, but after a point enzymes become too saturated so no more substrate can fit
• Carbohydrase


  • Enzymes that break disaccharides and polysaccharides down into monosaccharides
  • Produced in your mouth, pancreas and small intestine
• Protease


  • Enzymes that break proteins down into amino acids
  • Produced in the stomach, pancreas and small intestine
• Lipase


  • Enzymes that break lipids into fatty acids and glycerol
  • Produced in the pancreas and small intestine
• Starch Iodine Test


  Iodine Solution + Test Sample. If it becomes a dark blue/black colour, starch is present
• Emulsion Test for Lipids


  Shake test substance with ethanol until dissolved, pour solution into water. If there are any lipids present, they will precipitate and show up as milky emulsion
• Biuret Protein Test


  Few drops of potassium hydroxide and add copper sulfate solution (blue), If there is protein, solution becomes purple
• Benedict's Test for Reducing Sugars

  Two spatulas of sample into test tube or 1 cm3 if sample is liquid, add same volume of Benedict's solution, place in tub in water bath (95 degrees) for few minutes. If colour becomes cloudy orange, reducing sugar is present
• Calorimetry


  • Calorimeter can be made by arranging a beaker of water above a burning sample. The change in temperature of the water is a direct measure of the energy within the sample
  • Energy in Food (J) = Mass of Water (g) X Temp Change of Water (C) X 4.2
• Diffusion


  • Overall movement of particles from an area of high concentration to an area of lower concentration (liquids and gases)
  • Only very small molecules can diffuse through cell membrane - Like glucose, amino acids, water and oxygen
  • Greater the difference in concentration, the quicker the rate of diffusion
  • Higher the temperature, the more kinetic energy, the quicker the particles move
  • The greater the surface area of the membrane, the faster the rate of diffusion
• Osmosis


  Net movement of water molecules across a partially permeable membrane from a region of high water concentration to an area of lower water concentration
• Active Transport


  Moving molecules against a concentration gradient and it also requires energy
• Water uptake in 1 hour


  Change in Mass X (60 mins / Length of experiment in minutes)
• Percentage change in mass

  (Mass at end – Mass at start / mass at start) X 100