Biology Paper 1

• Plant organs


  • Leaves - site of photosynthesis and transpiration
  • Roots - where water and minerals enter
  • Meristem - where new cells are made
• Xylem


  Long continuous tubes that transport water upwards
• Phloem


  Conveyor belts that transport sugars, food and sap up and down the plant
• Factors increasing transpiration rate

  • Higher temperature
  • Lower humidity
  • Increased air movement
• Chlorosis


  Yellowing of leaves due to magnesium deficiency
• Leaf structure


  • Waxy cuticle
  • Upper epidermis
  • Palisade mesophyll
  • Spongy mesophyll
  • Vascular bundle
  • Lower epidermis with stomata
• Stomata


  Holes in the lower epidermis that control gas exchange
• Communicable diseases


  Caused by pathogens that reproduce in the body and cause damage - viruses, bacteria, fungi, protists
• Virus


  Protein casing with genetic code that injects into cells, causing them to produce more virus
• Measles


  Viral disease that causes a rash and can be deadly, spread by droplets
• HIV/AIDS


  STD that compromises the immune system
• Bacterial diseases


  Release toxins that damage body cells, e.g. salmonella, gonorrhea
• Fungal diseases


  E.g. athlete's foot
• Protist diseases


  E.g. malaria, spread by mosquitoes
• Plant pathogens


  E.g. rose black spot, tobacco mosaic virus
• Immune system defences


  • Skin
  • Nose/trachea (mucus, acid, enzymes)
  • Digestive system
  • White blood cells (lymphocytes, phagocytes)
• Antibodies


  Produced by lymphocytes, neutralize pathogens and mark them for destruction
• Vaccines


  Expose immune system to dead/inert pathogens to produce antibodies
• mRNA vaccines


  Inject mRNA to trick cells into producing pathogen antigens
• Antibiotics


  Kill bacteria, but not viruses. Penicillin was the first one.
• Antibiotic resistance


  Bacteria can mutate to become resistant to antibiotics
• Drug development


  Extracted from plants/organisms, then synthesized. Undergo lab, animal and human trials.
• Monoclonal antibodies


  Made from clones of cells producing specific antibodies, used for treatment and diagnosis
• Photosynthesis


  Process in plant cells using chlorophyll to convert light energy, CO2 and water into glucose and oxygen
• Respiration


  Process that releases energy from glucose, opposite of photosynthesis
• Aerobic and anaerobic respiration

  Aerobic uses oxygen, anaerobic produces lactic acid
• Fermentation


  Anaerobic respiration in plant and yeast cells, producing ethanol and CO2
• Metabolism


  Sum of all chemical reactions in a cell or organism, including respiration, synthesis and breakdown
• Making Cultures Practical

  1. Lift lid of petri death towards flame( to sterilise air by moving microbes/ killing them)
  2. Put drop of culture on agar spread evenly
  3. Put discs of antibiotics on culture if needed
  4. Few bits of tape( to allow aerobic respiration) incubate at 25 degrees Celsius