Which of the following processes does not occur during photosynthesis?

Analyze the question: We need the one process that does NOT happen during photosynthesis.

Concept: Photosynthesis is the process by which green plants make food (glucose) using light energy, carbon (IV) oxide and water:

6CO₂ + 6H₂O → (light, chlorophyll) → C₆H₁₂O₆ + 6O₂

It has two stages:

• Light stage (in the grana): Chlorophyll absorbs sunlight energy. Water is split (photolysis), releasing oxygen and hydrogen.
• Dark stage (in the stroma): Carbon (IV) oxide is taken in (fixed) and reduced using the hydrogen to form glucose.

Checking each option:

• A. Energy from sunlight is absorbed: This happens. Chlorophyll traps light energy. ✔
• B. Carbon (IV) oxide is evolved: This does not happen. CO₂ is absorbed (used up) in photosynthesis, not given off. It is evolved in respiration. ✘
• C. Oxygen is evolved: This happens. Oxygen is released as a by-product from the splitting of water. ✔
• D. Water is split: This happens (photolysis of water). ✔

Answer: B. Carbon (IV) oxide is evolved is the process that does not occur during photosynthesis, because CO₂ is used up, not released.

Tip: Remember the opposites:

• Photosynthesis: takes in CO₂, gives out O₂
• Respiration: takes in O₂, gives out CO₂

When you see "evolved" in a question, ask yourself, "is this gas being given out?" For photosynthesis, only O₂ is given out.