Question

Which of the following is(are) TRUE about photosynthesis?

• A. In C3 plants the first organic product of carbon fixation is 3-phosphoglycerate
• B. In C4 plants the first organic product of carbon fixation is oxaloacetate
• C. Crassulacean acid metabolism occurs in succulent plants living in arid conditions
• D. Oxygen is generated from carbon dioxide

Hint:

In photosynthesis, oxygen is produced from water during the light reactions, while carbon fixation leads to the formation of organic molecules like 3-PGA in C3 plants.

Answer 1

The Correct Option is A, B, C

The question requires us to identify the true statements regarding photosynthesis from the given options. Let's analyze each statement:

1. In C3 plants, the first organic product of carbon fixation is 3-phosphoglycerate.
   This statement is true. In C3 plants, carbon dioxide is fixed through the Calvin cycle, where the first stable compound formed is 3-phosphoglycerate. This is a characteristic feature of C3 photosynthesis.
2. In C4 plants, the first organic product of carbon fixation is oxaloacetate.
   This statement is also true. In C4 plants, the first step of carbon fixation involves the enzyme PEP carboxylase fixing carbon dioxide to form oxaloacetate. This occurs before the Calvin cycle and is an adaptation to minimize photorespiration.
3. Crassulacean acid metabolism occurs in succulent plants living in arid conditions.
   This statement is true. CAM (Crassulacean Acid Metabolism) is a photosynthetic adaptation seen in succulent plants in arid environments. It allows these plants to open their stomata at night to minimize water loss.
4. Oxygen is generated from carbon dioxide.
   This statement is false. Oxygen generated during photosynthesis comes from the splitting of water molecules, not from carbon dioxide. The process is known as photolysis, primarily occurring in the light reactions of photosynthesis.

Based on the analysis, the correct statements regarding photosynthesis from the options provided are:

• In C3 plants, the first organic product of carbon fixation is 3-phosphoglycerate.
• In C4 plants, the first organic product of carbon fixation is oxaloacetate.
• Crassulacean acid metabolism occurs in succulent plants living in arid conditions.

Therefore, the correct answer consists of the first, second, and third options. These options accurately describe different pathways and adaptations in photosynthesis.