Photosynthesis

• Photosynthesis


  1. Takes place in the leaves

  2. Takes place in chloroplasts

  3. Chlorophyll absorbs light energy

  4. Converts carbon dioxide and water into glucose and oxygen
• Photosynthesis is an endothermic reaction that requires light energy
• Where plants get reactants for photosynthesis

  1. Carbon dioxide diffuses into leaves through stomata

  2. Water is taken up from soil by roots and transported to leaves via xylem
• Products of photosynthesis


  • Glucose is the main product
  • Oxygen is also produced but not as important
• Uses of glucose produced by photosynthesis

  • Cellular respiration
  • Making cellulose
  • Making starch
  • Making amino acids
  • Making oils and fats
• Plant growth rate is often dependent on the rate of photosynthesis
• Factors that affect the rate of photosynthesis are light intensity, temperature, carbon dioxide concentration, and amount of chlorophyll
• Chlorophyll molecules absorb photons of light, which excites electrons to higher energy levels.
• Photosynthesis involves two main stages: the light-dependent reactions and the light-independent reactions (Calvin cycle).
• During photosynthesis, chlorophyll captures light energy and converts it into chemical energy stored in glucose molecules.
• Chlorophyll is a green pigment found in the chloroplasts of plant cells that absorbs light energy for photosynthesis.
• Light absorption occurs in the thylakoid membranes of chloroplasts.
• Increasing light intensity increases the rate of photosynthesis up to an optimum level beyond which it decreases due to damage caused by excess heat.
• In plants, photosynthesis occurs primarily in leaves due to their large surface area exposed to sunlight.
• The light-dependent stage of photosynthesis takes place within the thylakoids of chloroplasts.
• The process of photosynthesis can be represented as CO2 + H2O → C6H12O6 + O2.
• Carbon dioxide enters through stomata on the undersides of leaves and water enters via roots.
• Glucose produced during photosynthesis is used for respiration or converted into other organic compounds such as starch, cellulose, proteins, fats, etc.
• Photosystem II (PSII) is responsible for splitting water molecules into oxygen gas and hydrogen ions.
• Water molecules are absorbed into the leaf via osmosis.
• Photosynthetic pigments absorb different wavelengths of visible light, with chlorophyll absorbing mainly blue and red light.
• Light energy from the sun is absorbed by pigments called chlorophyll.
• Photosynthesis takes place in the chloroplast
• The process of photosynthesis involves two stages - the light-dependent reactions and the light-independent reactions.
• Carbon dioxide enters through stomata on the underside of leaves.
• Photosynthesis is an endothermic reaction because it requires energy from the surroundings
• Substances transported in plants: Water, minerals and sugar
• Water:

  • Needed for photosynthesis
  • Absorbed from the soil into the roots by osmosis
  • Transported upwards in the xylem
• Minerals:

  • Absorbed from the soil into the roots by active transport
  • Transported upwards in the xylem
• Sugar [sucrose]:

  • Glucose produced by photosynthesis is converted into sucrose to be transported
  • Transported in the phloem
  • Sugar transported upwards and downwards
• Water transport in plants

  Water is absorbed by the roots and transported up to the leaves through the xylem tissue. This process is called transpiration.
• Mineral transport in plants

  Minerals are absorbed by the roots and transported up to the leaves through the xylem tissue. These minerals are essential nutrients for the plant's growth and development.
• Sugar transport in plants

  Sugar is produced in the leaves through photosynthesis and transported to other parts of the plant through the phloem tissue. This process is called translocation and it provides energy for the plant's growth and development.
• 1st stage of photosynthesis

  • light energy splits water into hydrogen ions and oxygen
• 2nd stage of photosynthesis

  • CO2 combines with hydrogen to make glucose
• Stomata are the tiny openings on the underside of the leaf that allow gases to pass in and out
• Stomata controls water loss by changing the size of the pores