L33: Photosynthesis

• What is the primary source of free energy for biological systems?

  Solar energy trapped by photosynthesis
• How much free energy does photosynthesis store globally each year?

  About $10^{18} \text{ kJ}$
• What is the waste product of photosynthesis?

  Oxygen
• What role do stomata play in photosynthesis?

  They allow the exchange of air, including $H_2O$ and $CO_2$
• What are the two main stages of photosynthesis?

  Light-dependent reactions and light-independent reactions
• What is the significance of capturing photons in photosynthesis?

  It results in high energy electrons
• Which type of light has more energy, blue or red?

  Blue light has more energy than red light
• What does the energy of a photon depend on?

  Its wavelength
• What is the central metal ion in chlorophyll?

  Magnesium ($Mg^{2+}$)
• What does the Hill reaction demonstrate in photosynthesis?

  It shows that the primary event is the light-driven transfer of an electron
• What is the function of the light harvesting complex in photosynthesis?

  It captures photons and transfers energy to the reaction center
• What happens to the excited electron in the reaction center?

  It can be transferred to other molecules in a series of redox reactions
• What is the "red drop" phenomenon in photosynthesis?

  It refers to the increase in wavelength and decrease in energy affecting photosynthetic rate
• What is the terminal electron acceptor in the light-dependent reactions?

  NADP⁺
• What does the Z Scheme illustrate in photosynthesis?

  It shows the changes in redox potential during the light reactions
• What is unique about the enzyme in Photosystem II?

  It is the only enzyme able to split water
• Why is Rubisco considered a poor enzyme?

  It has slow catalytic activity and can react with oxygen, leading to photorespiration
• How do C4 plants avoid photorespiration?

  They concentrate $CO_2$ at the site of the Calvin cycle
• What is the overall efficiency of photosynthesis based on the given data?

  Approximately 30%
• What are the steps involved in the light-dependent reactions of photosynthesis?

  1. Capture of photons
  2. Conversion of light energy to ATP and NADPH
  3. Production of oxygen as a waste product
• What are the main steps of the Calvin cycle?

  1. Carbon fixation
  2. Reduction of 3-phosphoglycerate to Glyceraldehyde-3-phosphate (G-3-P)
  3. Regeneration of RuBP
• What are the two types of carbohydrates produced during photosynthesis and their functions?

  • Sucrose: mobile sugar for distribution
  • Starch: storage form of energy in chloroplasts and seeds
• What are the key differences between light and dark reactions in photosynthesis?

  • Light reactions: Produce NADPH and ATP, involve light harvesting
  • Dark reactions: Calvin cycle, interact with gluconeogenesis and PPP pathways
• What is the role of chlorophyll in photosynthesis?

  It absorbs light energy
• How does the proton gradient contribute to ATP production in photosynthesis?

  It drives ATP synthesis through ATP synthase
• What is the function of the thylakoid membrane in photosynthesis?

  It houses the light-dependent reactions and electron transport chain
• How does gluconeogenesis relate to the Calvin cycle?

  It provides intermediates for the synthesis of glucose from non-carbohydrate sources
• What is the role of auxiliary pigments in photosynthesis?

  They assist chlorophyll in capturing light energy
• What is the significance of the Mn cluster in Photosystem II?

  It facilitates the splitting of water molecules
• How does photosynthesis relate to cellular respiration?

  Photosynthesis produces glucose and oxygen, which are used in cellular respiration
• What environmental factors can impact the rate of photosynthesis?

  Light intensity, carbon dioxide concentration, and temperature
• What is the difference between cyclic and non-cyclic photophosphorylation?

  Cyclic photophosphorylation produces ATP only, while non-cyclic produces both ATP and NADPH