Biology B8

• What is the definition of photosynthesis?

  Photosynthesis is a chemical reaction in which energy is transferred from the environment as light from the Sun to the leaves of a plant.
• What type of reaction is photosynthesis?

  Photosynthesis is an endothermic reaction.
• What pigment absorbs light energy in plants?

  Chlorophyll absorbs light energy in plants.
• Where is chlorophyll found in plants?

  Chlorophyll is found in chloroplasts in the leaves of plants.
• What is a limiting factor in the context of photosynthesis?

  A limiting factor is anything that limits the rate of a reaction when it is in short supply.
• What are the limiting factors for photosynthesis?

  • Temperature
  • Carbon dioxide concentration
  • Light intensity
  • Amount of chlorophyll
• How does less chlorophyll affect photosynthesis?

  Less chlorophyll in the leaves reduces the rate of photosynthesis.
• How can more chlorophyll be produced in plants?

  More chlorophyll may be produced by plants in well-lit areas to increase the photosynthesis rate.
• Why is the rate of photosynthesis low at low temperatures?

  At low temperatures, the rate of photosynthesis is low because the reactant molecules have less kinetic energy.
• What happens to enzymes at high temperatures during photosynthesis?

  At high temperatures, the enzymes are denatured and the rate of photosynthesis quickly decreases.
• How does increasing carbon dioxide concentration affect photosynthesis?

  Increasing carbon dioxide concentration increases the rate of photosynthesis.
• What happens to the rate of photosynthesis when another factor becomes limiting?


  At a certain point, another factor becomes limiting, and the rate of photosynthesis will stop if there is little or no light.
• What is the relationship between light intensity and distance from a light source?

  As the distance of a light source from a plant increases, the light intensity decreases, which is called an inverse relationship.
• What is the inverse square law in relation to light intensity?

  The inverse square law states that light intensity varies in inverse proportion to the square of the distance: light intensity ∝ $\frac{1}{distance^2}$.
• If the distance between a light source and a plant is doubled, how does light intensity change?

  Light intensity falls by three-quarters if the distance is doubled.
• How do limiting factors interact in photosynthesis?

  • Limiting factors often interact, and any one may be limiting photosynthesis.
  • Example: Low curve has both carbon dioxide and temperature limiting.
  • Middle curve shows temperature as limiting.
  • Highest curve shows increased rates with both temperature and carbon dioxide until another factor becomes limiting.
• What are the uses of glucose produced in photosynthesis?

  • Convert into insoluble starch for storage
  • For respiration to produce energy
  • Produce fat or oil (lipids) for storage
  • Produce cellulose to strengthen cell walls
  • Produce amino acids for protein synthesis (requires nitrate ions)
• What is the chemical equation for photosynthesis?


  6CO2+ 6H2O → C6H12O6+ 6O2
• What do plants need from the soil for protein synthesis?

  Plants need nitrate ions from the soil for protein synthesis.
• Photosynthesis equation


  carbon dioxide + water → glucose + oxygen