Photosynthesis

• Photosynthesis is the building up of carbohydrates(glucose) from carbon dioxide and water using radiant energy from the Sun that is trapped by chlorophyll. Oxygen is released.
• Raw materials required for photosynthesis:

  1. Carbon dioxide from the atmosphere
  2. Water from the soil
  3. Radiant energy from the sun
  4. Chlorophyll in the chloroplasts of green plants
  5. Enzymes
• Products of photosynthesis:

  1. Glucose, which is stored in the plant as starch.
  2. Oxygen, which is released into the atmosphere.
• Light phase — takes place in the presence of light (light dependent).

  Dark phase — takes place in light or darkness (light independent).
• Light Phase:

  • Takes place in the grana of chloroplasts.
  • Radiant energy from the sun is absorbed by the chlorophyll molecules in thylakoids.
  • Energy transformation takes place and radian energy is transformed into chemical energy.
  • The chemical energy is used for two processes: Photolysis, the energy carrier ATP is formed and is used again in the dark phase.
• Dark Phase:

  • Takes place in the stroma of chloroplasts.
  • Carbon dioxide that is absorbed from the atmosphere combined with the energy rich H-atoms from the light phase using the energy that is released from ATP.
  • Energy rich carbohydrates(glucose) are formed.
  • Excess glucose is converted to starch for storage.
• Importance of photosynthesis:

  1. It keeps the oxygen concentration in the atmosphere and water constant , as oxygen which is required by organisms for cell respiration is released during photosynthesis.
  2. Photosynthesis keeps the level of carbon dioxide in the atmosphere and water constant, as the carbon oxide is released during cellular respiration is absorbed during photosynthesis.
  3. Photosynthesis provides food for heterotropic organisms, as fats and proteins are also made from the glucose and starch that are produced during photosynthesis.
• Importance of photosynthesis


  • Keeps the oxygen concentration in the atmosphere and water constant
  • Keeps the level of carbon dioxide in the atmosphere and water constant
  • Provides food for heterotropic organisms
  • Makes chemical energy available for cell functioning
• Photosynthesis


  1. Oxygen released

  2. Carbon dioxide absorbed

  3. Glucose and starch produced

  4. Radiant energy trapped and transformed into chemical energy
• Oxygen released during photosynthesis


  Required by organisms for cell respiration
• Carbon dioxide released during cellular respiration


  Absorbed during photosynthesis
• Importance of photosynthesis


  • Keeps the oxygen concentration in the atmosphere and water constant
  • Keeps the level of carbon dioxide in the atmosphere and water constant
  • Provides food for heterotropic organisms
  • Makes chemical energy available for cell functioning
• Glucose and starch produced during photosynthesis


  Used to make fats and proteins
• Radiant energy trapped and transformed into chemical energy during photosynthesis


  Can be released during cellular respiration
• Photosynthesis


  1. Oxygen is released

  2. Carbon dioxide is absorbed

  3. Glucose and starch are produced

  4. Radiant energy is trapped and transformed into chemical energy
• Oxygen is required by organisms for cell respiration


  Oxygen is released during photosynthesis
• Carbon dioxide is released during cellular respiration


  Carbon dioxide is absorbed during photosynthesis
• Glucose and starch are produced during photosynthesis

  Fats and proteins are also made from them
• Radiant energy is trapped and transformed into chemical energy during photosynthesis


  Chemical energy is released during cellular respiration
• The glucose produced in photosynthesis is stored in the form of starch.
• Factors that influence the rate of photosynthesis:

  1. Light intensity. The increase in light intensity results in an increase in the rate of photosynthesis but only to a maximum level.
  2. Temperature. At low temperatures enzymes become inactive and it hide temperatures enzymes denature.
  3. Carbon dioxide concentration. A decrease in CO2 concentration leads to a decrease in the rate of photosynthesis. An increase in CO2 concentration leads to an increase in the rate of photosynthesis.
• The optimum growth temperature for most plants is between 10° c and 29.5° c.
• When a plants rate of photosynthesis increases more glucose is produced and stored as starch. The glue glucose/starch is a source of energy for growing, which means that an optimal rate of photosynthesis will promote the growth plants.
• The aim of a greenhouse is to promote optimal conditions of light, temperature and CO2 for maximum growth of the cultivated plants.
• Optimum light intensity accelerates photosynthesis and stimulates the growth rate of plants.
• Optimum temperature must be possible to regulate the temperature of the air in the greenhouse to keep it for maximum growth of specific plant types.
• CO2 enrichment


  Increasing the CO2 levels in the air surrounding a plant to increase its rate of photosynthesis, growth rate and quality
• During the day


  CO2 levels can decrease greatly due to photosynthesis
• CO2 cannot penetrate the greenhouse, because it is a fairly closed system
• CO2 enrichment on a large scale

  Pumping CO2 gas from tanks into the greenhouse
• Increasing CO2 levels


  1. Addition of sodium bicarbonate

  2. Addition of organic materials to the soil
• Increasing CO2 levels


  Decomposition bacteria in the soil becoming more active and releasing CO2 during decomposition
• Purpose of the stroma:

  • Excess glucose is stored here
  • Enzymes for photosynthesis
  • Dark Phase occurs here
• Purpose of Thylakoids:

  • Membranous sacs contain chlorophyll
• Purpose of Grana/Granum:

  • stacks of thylakoids
  • Light Phase occurs here
• Purpose of Intergrana/Lamella:

  • keeps stacks of thylakoids apart from each other
• What is Radiant energy:

  • Energy from the Sun
  • Light and Heat energy