Photosythesis

• In chloroplasts, what do different pigments absorb?

  Different wavelengths of light
• What three main factors affect the rate of photosynthesis?

  • Light intensity
  • $CO_2$ concentration
  • Temperature
• How can the limiting factors of photosynthesis be overcome?

  Using lights, increasing $CO_2$, and greenhouses
• How many stages does photosynthesis consist of?

  Two
• What is produced in the light-independent stage of photosynthesis?

  Food for the plant, like glucose
• What happens to chlorophyll during photoionisation?

  It excites and loses two electrons
• What do the light-dependent stages of photosynthesis provide?

  Reactants for light independent reaction
• What process replaces the electrons lost by chlorophyll during photoionisation?

  Photolysis of water
• In photoionisation, where do the excited electrons move?

  To a new energy level
• During photolysis, what is water split into by light?

  Electrons, protons, and oxygen
• What is the role of protons during the photolysis of water?

  Maintain high proton concentration
• What happens to the oxygen produced during the photolysis of water?

  It diffuses out or is used
• Where is light absorbed in the light-dependent reaction?

  By a protein complex
• What happens to the energy after light absorption in the light-dependent reaction?

  Transferred to a pair of electrons
• What happens to the electrons after they are excited in light dependent reactions?

  They move out of chlorophyll
• Where do the new electrons come from to replace those that left the chlorophyll?

  From splitting of water
• How do electrons move along the proteins in the light dependent reaction?

  Via redox reactions
• In the light dependent reaction, what is transported by the protein complex using energy?

  Protons
• What gradients are ensured by the active transport of protons?

  Proton gradients
• In the light-dependent reaction, what do the electrons react with at the end of the ETC?

  NADP and H+
• How do protons diffuse back as a result of the proton gradient?

  Via ATP synthase
• From what substances is ATP formed via chemiosmosis?

  ADP and Pi
• What is released when protons diffuse back via ATP synthase and what is it used for?

  Energy, to form ATP
• What are the main adaptations of chloroplasts for photosynthesis?

  • Large surface area maximises amount of ATP and NADPH produced
  • Lamella arrangement allows maximum absorption
  • Membranes are selectively permeable to maintain proton gradient
  • Contain ribosomes and DNA so proteins are produced easily
• Where does the light-independent reaction take place?

  In the stroma
• What are the reactants in the light-independent reaction?

  $CO_2$, NADPH, and ATP
• What are the products of the light-independent reaction?

  Useful organic substances
• What molecule does $CO_2$ react with when it enters the stroma?


  Ribulose bisphosphate
• What enzyme catalyses the reaction between $CO_2$ and ribulose bisphosphate?


  Rubisco
• What is formed when $CO_2$ reacts with ribulose bisphosphate?


  2 molecules of glycerate-3-phosphate
• What are glycerate-3-phosphates converted into?

  Triose phosphates
• What provides the energy for the conversion of glycerate-3-phosphates into triose phosphates?

  ATP hydrolysis
• What reduction reaction helps glycerate-3-phosphates get converted into triose phosphates?

  Oxidation of NADPH to NADP
• What percentage of triose phosphates are converted back to ribulose bisphosphate?

  80%
• What is used to convert triose phosphates back into ribulose bisphosphate?

  ATP
• What do the remaining triose phosphates that are not converted to RuBP form?

  A range of organic substances
• Where do ADP, Pi, and NADP return after the light-independent reaction?

  To thylakoid for LDR
• What happens to the rate of the light-independent reaction as light intensity increases?

  It increases
• How does increased light intensity affect ATP and NADPH production?

  It increases production
• As $CO_2$ concentration increases, what happens to the rate of conversion of ribulose bisphosphate into glycerate-3-phosphate?


  It increases