State that within a chloroplast, the thylakoids (thylakoid membranes and thylakoid spaces), which occur in stacks called grana, are the site of the light-dependent stage and the stroma is the site of the light-independent stage

Sourav PanOctober 31, 2024

Answered

Chloroplast Structure and Photosynthetic Stages

Within a chloroplast, distinct regions facilitate the two stages of photosynthesis:

1. Light-Dependent Stage (Light Reactions):
   • Location: Thylakoids (Thylakoid Membranes and Thylakoid Spaces)
   • Arrangement: Stacks called Grana
   • Processes:
     • Light absorption by pigments (e.g., chlorophyll)
     • Exciton transfer and electron transport
     • ATP and NADPH synthesis (via photophosphorylation)
2. Light-Independent Stage (Calvin Cycle):
   • Location: Stroma
   • Processes:
     • CO2 fixation (via RuBisCO)
     • Reduction of fixed CO2 to glucose (using ATP and NADPH from the Light-Dependent Stage)

Key Points from the Provided Web Search Results:

• Thylakoids/Grana:
  • Disc-shaped structures stacked in grana (singular: granum)
  • Contain chlorophyll and are the site of light-dependent reactions
  • Thylakoid membrane envelops the thylakoid lumen
• Stroma:
  • Protein-rich, alkaline, aqueous fluid surrounding the grana
  • Equivalent in function to the mitochondrial matrix
  • Site of the chloroplast genetic system and metabolic enzymes, including those for CO2 conversion to carbohydrates