B4

• Structure of the leaf:

  • Thin to allow light to travel through
  • Broad with a large surface area
  • Network of veins (xylem and phloem) for substance transport
  • Contains chlorophyll for photosynthesis
  • Flat and not overlapping to maximize light absorption
  • Waxy cuticle on top to prevent water loss
  • Palisade cells for photosynthesis
  • Guard cells at the bottom with stomata for gas exchange
• Photosynthesis Word and Symbol Equations:

  • Word equation: Carbon dioxide + water -> glucose + oxygen
  • Symbol equation: CO2 + H2O -> C6H12O6 + O2
  • Light and chlorophyll are needed for the reaction to occur
• Xylem and Phloem:

  • Phloem carries sugar (translocation)
  • Xylem carries water and minerals from roots to leaves
  • Water escapes through stomata, more drawn up through xylem
• Factors affecting Photosynthesis:

  • Light intensity: increases photosynthesis rate up to optimum point
  • Carbon dioxide: increases rate until optimum, can be adjusted in a greenhouse
  • Temperature: optimum temperature for enzyme activity
  • Chlorophyll: more chlorophyll increases photosynthesis rate
• Limiting Factors of Photosynthesis:

  • Light, carbon dioxide, and temperature can be limiting factors
  • Adjusting factors can increase photosynthesis rate up to optimum point
• Uses of Glucose from Photosynthesis (SCARF):

  • Starch: storage for later use
  • Cellulose: strengthens cell walls
  • Amino acids: used for protein synthesis (growth and repair)
  • Respiration: glucose used for energy
  • Fats and oils: stored for energy
• Graph Analysis:

  • Plants do more photosynthesis than respiration during the day
  • Carbon dioxide levels decrease during the day due to photosynthesis
  • Oxygen levels decrease at night due to reduced photosynthesis
• Photosynthesis reduces carbon dioxide levels because it uses carbon dioxide
• Oxygen levels decrease at night due to respiration and increase during the day due to photosynthesis
• Transpiration is the movement of water through the xylem, drawing water up through the roots to the leaves
• Increasing the number of leaves or temperature can lead to a faster rate of photosynthesis
• Starch can be used to test for excess glucose produced through photosynthesis
• Aerobic respiration is efficient and requires oxygen, while anaerobic respiration is less efficient and does not use oxygen
• To test for starch in a leaf, boil it, then use ethanol to remove chlorophyll before applying iodine solution
• Lactic acid is produced in muscles during anaerobic respiration, causing fatigue and an oxygen debt
• Yeast undergo anaerobic respiration, producing ethanol and carbon dioxide, used in fermentation for alcoholic drinks and bread making
• Metabolism includes all reactions in the body, with respiration providing energy for other reactions
• High metabolism leads to efficient energy use, while low metabolism can result in weight gain
• Michael Phelps had a high metabolic rate due to more mitochondria, requiring a high calorie intake during the Olympics
• Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll
• Photosynthesis equation:

  • Carbon dioxide + water (+ light energy) → glucose + oxygen
• Photosynthesis takes place in the chloroplasts of plant cells
• Factors affecting photosynthesis:

  • Light intensity
  • Carbon dioxide concentration
  • Temperature
• Limiting factors of photosynthesis:

  • The factor that is in the shortest supply and limits the rate of photosynthesis