Photosynthesis

• Plants are able to make their own food by photosynthesis
• During photosynthesis, photosynthetic organisms, such as green plants and algae, use energy from the Sun or an artificial source to make glucose
• When photosynthetic organisms use energy from the sun or an artificial source to make glucose, some of the glucose is used to make larger, complex molecules that the plants or algae need to grow - these make up the organism's biomass; the mass of living material
• The energy stored in the organisms' biomass works its way through the food chain as animals eat them and each other. So ultimately, photosynthetic organisms support nearly all life on Earth
• Photosynthesis happens inside chloroplasts - they contain chlorophyll which absorbs light. Energy is transferred to the chloroplasts from the environment by light.
• The equation for photosynthesis:


  Carbon dioxide + water -> light -> glucose + oxygen
• Carbon dioxide + water -> light -> glucose + oxygen


  6CO2 + 6H2O -> chlorophyll -> C6H12O6 + 6O2
• Photosynthesis is an endothermic reaction - energy is transferred from the environment during it
• Photosynthesis happens in two main stages :

  Energy is transferred by light used to split water into oxygen gas and hydrogen ions.

  Carbon dioxide gas then combines with the hydrogen ions to make glucose
• Photosynthesis is the chemical process in which plants that contain chlorophyll covert light energy into chemical energy in the form of glucose
• Where does photosynthesis take place in a plant?

  In the leaves, specifically chloroplasts
• What pigment in chloroplasts absorbs light?

  Chlorophyll
• What does chlorophyll absorb from the environment?

  Light energy
• What are the reactants in the photosynthesis equation?

  Carbon dioxide and water
• Why is light written above the reaction line in the photosynthesis equation?

  Because the reaction requires light energy
• What type of reaction is photosynthesis classified as?

  Endothermic reaction
• How is energy transferred to chloroplasts during photosynthesis?

  By light from the environment
• How does carbon dioxide enter the leaves?

  Through the stomata
• How is water transported to the leaves?

  Via the xylem
• What is the main product that plants want from photosynthesis?

  Glucose
• What do plants sometimes use the oxygen produced in photosynthesis for?

  For respiration
• What are the five main uses of glucose in plants?

  Respiration, cellulose, starch, amino acids, oils
• How does respiration relate to glucose in plants?

  It breaks glucose apart to release energy
• What is cellulose made from?

  Lots of glucose molecules combined
• Why is starch a better form of glucose for storage?

  It is more compact and insoluble
• When do plants typically break down starch to glucose?

  When photosynthesis isn't happening much
• How do plants make amino acids?

  By combining glucose with nitrate ions
• What do plants use amino acids to make?

  Proteins
• Why is glucose essential for plants?

  It affects their growth rate
• What factors affect the rate of photosynthesis?

  • Light intensity
  • Temperature
  • Carbon dioxide concentration
  • Amount of chlorophyll
• What is the process that plants use to trap light energy?

  Photosynthesis
• What type of reaction is photosynthesis?

  Endothermic reaction
• From where do plants derive energy for growth?

  From light energy trapped by photosynthesis
• Where does photosynthesis take place in a plant?

  In the leaves
• What green chemical in leaves absorbs light energy?

  Chlorophyll
• What are the two main substances that plants take in for photosynthesis?

  Carbon dioxide and water
• What is produced as a byproduct of photosynthesis?

  Oxygen
• What is the word equation for photosynthesis?

  Carbon dioxide + water → glucose + oxygen
• What is the chemical formula for oxygen?

  O₂
• What happens to the rate of photosynthesis when light intensity is increased?

  The rate of photosynthesis increases