(e) Nutrition

• Photosynthesis is an endothermic reaction where energy from sunlight is transferred to the chloroplasts in green plants
• Chlorophyll, a green pigment found inside chloroplasts, absorbs energy from sunlight
• Green plants use this energy to produce the carbohydrate glucose from carbon dioxide and water
• Oxygen is produced and released as a waste product during photosynthesis
• Photosynthesis is the process by which plants manufacture carbohydrates from raw materials using energy from light
• Plants are autotrophs, capable of making complex molecules like glucose from simple molecules like carbon dioxide and water
• Plants are producers as they can make their own food, making them the first organism at the start of all food chains
• Products of photosynthesis:

  • Plants use glucose as a source of energy in respiration
  • Glucose can be used to produce starch for storage
  • Glucose can be used to synthesize lipids for an energy source in seeds
  • Glucose can be used to form cellulose for making cell walls
  • Glucose can be used to produce amino acids (used to make proteins) when combined with nitrogen and other mineral ions absorbed by roots
• Word equation for photosynthesis

  Answer:

  
• Balanced chemical equation for photosynthesis

  Answer:

  
• There are three main factors that limit the rate of photosynthesis:

  1. Temperature
  2. Light intensity
  3. Carbon dioxide concentration
• Temperature affects the speed at which carbon dioxide and water move through a plant
• Lower temperatures result in less kinetic energy for particles, leading to fewer successful collisions over time
• Increasing temperature increases the kinetic energy of particles, enhancing the likelihood of collisions between reactants and enzymes, resulting in the formation of products
• At higher temperatures, enzymes involved in photosynthesis can be denatured, reducing the overall rate of photosynthesis
• Light intensity

  • The intensity of the light available to the plant will affect the amount of energy that it has to carry out photosynthesis
  • The more light a plant receives, the faster the rate of photosynthesis
  • This trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply
• Carbon dioxide concentration

  • Carbon dioxide is one of the raw materials required for photosynthesis
  • This means the more carbon dioxide that is present, the faster the reaction can occur
  • This trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply
• Chlorophyll

  • The number of chloroplasts (as they contain the pigment chlorophyll which absorbs light energy for photosynthesis) will affect the rate of photosynthesis
  • The more chloroplasts a plant has, the faster the rate of photosynthesis
  • The amount of chlorophyll can be affected by:
  • Diseases (such as tobacco mosaic virus)
  • Lack of nutrients (such as magnesium)
  • Loss of leaves (fewer leaves means fewer chloroplasts)
• What is the function of the wax cuticle?

  Protective layer on top of leaf, prevents water from evaporating
• What is the function of the upper epidermis?

  Thin and transparent to allow light to enter through the PM layer underneath it
• What is the function of the palisade mesophyll?

  Column shaped cells tightly packed with chloroplasts to absorb more light, maximising photosynthesis
• What is the function of the spongy mesophyll?

  Contains internal air space to increase surface area to volume ratio for diffusion of gases (mostly C02)
• What is the function of the lower epidermis?

  Contains guard cells and stomata
• What is the function of the guard cell?

  Where gas exchange takes place; opens during the day, closes during the night. Evaporation of water takes place from here. In most plants, there is a greater concentration on the underside of the leaf to reduce water loss.
• What is the function of the vascular bundle?

  Contains xylem and phloem to transport substances to and from the leaf
• What is the function of the xylem?

  Transports water into the leaf
• What is the function of the phloem?


  Transports sucrose and amino acids around the plant.