Biology Required Practicals + Revision

• Osmosis


  Movement of water molecules from high to low concentration across a partially permeable membrane
• Potato chip experiment


  1. Cut 3 potatoes to same length (5cm chips)

  2. Weigh potatoes to record initial mass

  3. Measure 25cm3 of 3 different salt concentrations (weak salt, strong salt, plain water)

  4. Put chips in solution and leave for 30 minutes

  5. Remove chips, pat dry, weigh again

  6. Calculate % change in mass
• Independent Variable

  • Concentration
• Dependent Variable

  • Mass
• Control Variable

  • Length
• Food tests

  Preparing a table

  • Grind the food sample in a pestle and mortar
  • Add a small amount of water
  • Filter
  • Test the solution


  Tests

  1. Starch - Iodine (orange) - Black
  2. Protein - Biuret (blue) - Lilac
  3. Glucose - Benedict’s (blue- water bath heat) - green, yellow, orange, red
  4. Fats - Ethanol - Cloudy layer on top
• Enzymes and pH

  A continuous sampling technique

  • Set up a water bath at 37° (body temp)
  • Place starch and amylase into the water bath and leave to acclimatise
  • Make a buffer pH solution of pH 1,7&14
  • Control Variable (starch)
  • pH7 works best, amylase breaks down starch


  First, add a small drop of starch in the wells and test with iodine

  Add amylase to starch, start the timer

  Test the sample every 30 seconds

  Remember to test more intervals

  (7.2,7.4,7.6)
• Respiration is a process which releases energy

  1. Trachea-Lungs-Bronchus-Bronchioles-Alveoli
  2. An Alveoli (villi in small intestines)- Why’s it good for gas exchange? -Thin walls -Moist -Near to blood capillaries -Increase surface area


  3. Mitochondria- Respiration

  Ribosomes- Proteinsynthesis

  In muscle cells, sperm cells, Root hair cells (active transport)

  Formula- Oxygen+Glucose— Carbon Dioxide+Water

  Exothermic Reaction
• Plants (Respiration+Photosynthesis) and Animals respire

  Aerobic respiration

  With oxygen

  In mitochondria


  Anaerobic respiration

  Limited/no oxygen

  In Cytoplasm

  Glucose isn’t properly broken down

  Lactic Acid produced
• Diffusion

  High-Low Concentration

  Made faster by… heat (kinetic energy), stirring, greater concentration, shorter distance, pressure
• Exercise

  • Pulse rate increases
  • To get more oxygen and more glucose into muscle cells
  • For respiration
  • To release energy
  • And get rid of more CO2 that is made
  • If anaerobic respiration happens, lactic acid is produced
  • An oxygen debt occurs
  • Pulse rate returns to normal once the lactic acid is broken doen
• Root Hair Cell - Active Transport

  • Getting ions into a cell (plants and animals) from low to high conc.
  • Mitochondria for respiration to release energy

  Small Intestine - Food molecules
• White Blood Cells

  1. Phagocyte engulfs and destroys the pathogen and antigen
  2. The Lymphocytes antibodies are specific to antegen
  3. The toxins make us sick so the lymphocytes antitoxins neutralise the toxins


  Defences (cilia cells)

  • Skin
  • Tears
  • Eyelashes
  • Scabs
  • Nose hairs
  • Stomach acid
  • White blood cells