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Zorluk: ZorPlant Biology and Photosynthesis

During photosynthesis, green plants convert solar energy, water (H2OH_2O), and carbon dioxide (CO2CO_2) into chemical energy and gas byproducts. If a plant is provided with water labeled with a heavy oxygen isotope (18O^{18}O), in which photosynthetic product will this labeled oxygen primarily be detected?

  1. A
    Glucose (C6H12O6C_6H_{12}O_6) molecules synthesized during the Calvin cycle
  2. Molecular oxygen gas (O2O_2) released during the light-dependent reactionsCevap
  3. C
    Carbon dioxide (CO2CO_2) gas released directly by chloroplasts
  4. D
    Cellulose fibers incorporated into the animal-like cell membrane

Cevap

Molecular oxygen gas (O2O_2) released during the light-dependent reactions
During the light-dependent reactions of photosynthesis within the thylakoid membranes of chloroplasts, photon energy drives photolysis, splitting H2OH_2O into hydrogen ions, electrons, and molecular oxygen. Consequently, all oxygen atoms released as atmospheric O2O_2 originate strictly from water. Therefore, labeling water with 18O^{18}O results directly in labeled O2O_2 gas.

Adım Adım Çözüm

1
Identify the stage of photosynthesis where water (H2OH_2O) is consumed.
Water is utilized during the light-dependent reactions occurring on the thylakoid membranes of chloroplasts.
Light energy is absorbed by chlorophyll to power the photolysis (splitting) of water molecules.
2
Determine the biochemical fate of the atoms derived from water splitting.
Water is split into protons (H+H^+), electrons (e−e^-), and diatomic oxygen gas (O2O_2).
Electrons replace those excited in photosystem II, while the oxygen atoms combine and are liberated into the atmosphere as O2O_2.
3
Trace the isotope 18O^{18}O from labeled water.
The 18O^{18}O label appears directly in the released O2O_2 gas rather than organic sugars.
The oxygen atoms in carbohydrates like glucose (C6H12O6C_6H_{12}O_6) are derived from the carbon dioxide (CO2CO_2) fixed during the Calvin cycle.

Anahtar Kavram

Photolysis of water in the light-dependent reactions of photosynthesis as the source of atmospheric oxygen
Tahmini Süre:1m 30s
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Konular

Plant Biology and Photosynthesis

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