The Oxygen evolved in photosynthesis comes from:
1) (CH2O).
2) water.
3) (C3H3O3).
4) carbon dioxide.
5) glucose.
The correct answer and explanation is:
The correct answer is 2) water.
During photosynthesis, oxygen is released as a byproduct, and this oxygen originates from water molecules. The process of photosynthesis occurs in two main stages: the light-dependent reactions and the light-independent reactions (Calvin cycle). The oxygen that is evolved in photosynthesis comes from the splitting of water molecules in the light-dependent reactions.
In the light-dependent reactions, sunlight is absorbed by chlorophyll and other pigments in the chloroplasts. This energy is used to split water molecules (H2O) into oxygen (O2), protons (H+), and electrons (e-). The oxygen atoms from these water molecules are released into the atmosphere as oxygen gas (O2). The protons and electrons play key roles in the production of energy-rich molecules like ATP and NADPH, which are used in the Calvin cycle to synthesize glucose.
Here’s a breakdown of the process:
- Water molecules are split by an enzyme complex known as the photosystem II during the light-dependent reactions.
- The energy from sunlight excites electrons in chlorophyll, which are then transferred through a series of proteins in the electron transport chain.
- This transfer generates a proton gradient across the thylakoid membrane, which is used to produce ATP.
- The oxygen atoms from water molecules are released into the atmosphere as O2, completing the oxygen evolution part of photosynthesis.
Thus, water is the direct source of the oxygen that is released during photosynthesis. Other options, such as carbon dioxide, glucose, and (CH2O) (which represents a basic sugar molecule), do not directly contribute to the evolution of oxygen. The oxygen atoms in carbon dioxide are involved in the formation of glucose, but they do not directly form oxygen gas during photosynthesis.