Energy Transfers

• What is the overall equation for photosynthesis?

  6CO₂ + 6H₂O → 6O₂ + C₆H₁₂O₆
• What are the structural adaptations of a leaf for photosynthesis?

  • Thin: Light absorbed in first few micrometres
  • Large surface area: Absorbs as much light as possible
  • Many stomata: Allows gas exchange with a short diffusion pathway
  • Air spaces: Allows rapid diffusion of CO₂ and O₂
• What is the primary pigment in the reaction centre of photosynthesis?

  Chlorophyll a
• What are the specific wavelengths associated with P700 and P680 in chlorophyll a?

  P700 is in photosystem I and P680 is in photosystem II (680nm)
• What color does chlorophyll a appear and what light does it absorb?

  Chlorophyll a appears yellow-green and absorbs red light and blue light at 450nm
• What essential atom is contained in chlorophyll a?

  Magnesium (Mg)
• What happens to electrons in chlorophyll a when light hits it?

  A pair of electrons become excited
• What is the role of chlorophyll b in photosynthesis?

  It is an accessory pigment that absorbs light at wavelengths between 500-640nm
• What color does chlorophyll b appear?

  Chlorophyll b appears blue-green
• What type of light do carotenoids absorb and reflect?

  Carotenoids absorb blue light and reflect yellow and orange light
• What is the significance of carotenoids in photosynthesis?

  They absorb light not normally absorbed by chlorophyll
• What is the first step in the light-dependent reaction of photosynthesis?

  Light is absorbed by Photosystem II
• What happens to electrons when they are excited in Photosystem II?

  They travel to the electron transport chain
• How is ATP produced during the light-dependent reactions?

  Electrons lose energy as they pass through the electron transport chain, which is used for ADP + pi → ATP
• What is the process called when ATP is formed in the light-dependent reactions?

  Photophosphorylation
• What occurs to the electron in Photosystem I when it is excited by light?

  It goes to an electron acceptor
• What is the result of the electron losing energy in Photosystem I?

  It is used to reduce NADP to NADPH
• What is photolysis in the context of photosynthesis?

  It is the splitting of water using light
• What are the products of photolysis?

  H⁺ ions, electrons, and oxygen
• What are the main steps of the Calvin Cycle in the light-independent reactions?

  • CO₂ diffuses into the leaf
  • Combines with RuBP
  • Produces 2 molecules of 3C compound
  • Rubisco catalyzes the reaction
  • NADPH reduces GP to TP
  • ATP from LDR provides energy
  • Protons come from NADPH
  • TP is used to make organic compounds like glucose
• What enzyme catalyzes the reaction in the Calvin Cycle?

  Rubisco
• What happens to GP in the Calvin Cycle?

  It is reduced to TP by NADPH
• What is the role of ATP in the Calvin Cycle?

  It provides energy for the reactions
• What happens to TP produced in the Calvin Cycle?

  It is used to make organic compounds like glucose
• What are the factors affecting photosynthesis?

  • Temperature: Enzymes work within specific temperature ranges
  • Below 10°C: Inactive
  • Above 45°C: May denature
  • CO₂ levels: Low CO₂ slows the Calvin Cycle
  • Water: Too little stops the reaction; too much disrupts ATP and NADPH production
  • Light intensity: Affects the rate of photosynthesis until saturation point
• What happens to the rate of photosynthesis when CO₂ levels are low?

  Rubisco can't convert RuBP to GP, slowing down the Calvin Cycle
• What is the compensation point in photosynthesis?

  It is the level of light intensity where the rate of photosynthesis equals the rate of respiration
• What happens to enzymes at temperatures below 10°C?

  They become inactive
• What can happen to enzymes at temperatures above 45°C?

  They may denature
• How does too much water affect photosynthesis?

  It can lead to waterlogged soil, disrupting ATP and NADPH production
• What is the relationship between light intensity and the rate of photosynthesis?

  The rate of photosynthesis increases with light intensity until a saturation point is reached
• What is the saturation point in photosynthesis?

  It is the point where increasing light intensity does not increase the rate of photosynthesis
• What happens to RuBP when CO₂ levels are low?

  It accumulates, slowing down the Calvin Cycle
• What is the effect of increasing light intensity after the saturation point?

  It does not increase the rate of photosynthesis
• What is the first step of glycolysis involving glucose?

  Glucose is phosphorylated to form glucose phosphate.
• Where does glycolysis take place in the cell?

  Glycolysis takes place in the cytoplasm of the cell.
• What does glucose phosphate turn into during glycolysis?

  Glucose phosphate turns into 2 triose phosphate molecules.
• How many pyruvate molecules are produced from 2 triose phosphate molecules?

  2 pyruvate molecules are produced.
• What are the main inputs and outputs of glycolysis?

  • Inputs:
  • Glucose (6C)
  • 2 NAD
  • 4 ADP
  • Outputs:
  • 2 Pyruvate (3C)
  • 2 NADH
  • 4 ATP (net gain of 2 ATP)
• What happens to pyruvate molecules in the link reaction?

  Pyruvate molecules are actively transported into the matrix of the mitochondria.