BIO PAPER 1

• Epidermis


  Covers outer surfaces of plant for protection
• Palisade mesophyll


  • Main site of photosynthesis
• Spongy mesophyll


  • Air spaces between cells allow gases to diffuse through leaf
• Xylem


  Transports water and minerals through plant, supports the plant
• Phloem


  Transports dissolved food materials
• Meristem tissue


  Found at tips of roots and shoots where it produces new cells for growth
• Stomata


  Allows diffusion of gases in and out of leaf, can be opened and closed by guard cells
• Xylem cells


  • Arranged end to end but end walls break down to form hollow tubes, cell walls strengthened by lignin
• Phloem


  • End walls allow sugars through, support the tubes
• Transpiration


  1. Water evaporates and diffuses out of stomata

  2. Helps draw water up xylem vessels from roots
• Factors affecting rate of transpiration

  • Increase in temperature (more energy transferred to water to evaporate)
  • Faster air flow (moves water vapour away allowing more to evaporate)
  • Increased light intensity (causes stomata to open)
  • Increase in humidity (decreases rate as it contains more water vapour so concentration gradient is lower)
• Guard cells

  Open and close stomata, closing stomata reduces water loss when water is scarce
• Translocation


  Phloem tissue transporting dissolved sugars from leaves to rest of plant
• Immune system

  • Physical and chemical barriers
  • White blood cells (patrol body)
  • Phagocytosis (engulfs pathogens)
  • Producing antitoxins (bind and counteract toxins)
  • Producing antibodies (lock onto foreign antigens)
• Vaccination


  Contains weakened pathogens that body still treats like proper pathogens, allowing it to develop immunity
• Vaccines work against bacteria and viruses
• Vaccines don't always grant full immunity and can have bad reactions (rare)
• Drugs


  Medication that can relieve symptoms or treat the disease
• Antibiotics


  Directly kill bacteria or prevent their growth, need to test for which bacteria before prescribing
• Drug testing


  1. Preclinical testing on cells and tissues

  2. Stage 1 testing on live animals

  3. Stage 3 clinical testing on healthy volunteers and those with illness
• Drug testing


  • Evaluates efficacy (how well it works) and toxicity (how harmful it is)
  • Determines optimal dosage
• Placebo


  Looks like the real drug but doesn't do anything, used in blind and double-blind trials to ensure fairness and valid results
• Cellular respiration


  Exothermic reaction which transfers energy from glucose, continuously occurring in living cells
• Aerobic respiration

  Takes place when there is enough oxygen, most efficient way to transfer energy from glucose
• Anaerobic respiration


  Respiration without oxygen, incomplete breakdown of glucose resulting in lactic acid buildup
• Exercise


  Increases breathing rate, heart rate, and blood flow to deliver more oxygen to muscles
• Lactic acid builds up during anaerobic respiration and must be removed by reacting with oxygen
• Mitosis

  Process of making new cells for growth and repair (when nucleus divides)
• Cell cycle

  1. Interphase

  2. Phase (organelles duplicate and enlarge)

  3. S Phase (DNA duplicates)

  4. G₂ Phase (DNA checked and corrected)

  5. Nucleus divides

  6. Cytokinesis (cell divides)
• Diploid cells have 46 chromosomes, all unique
• Haploid cells have 23 chromosomes