Question

1. Why is C3 photosynthesis inefficient when the concentration of CO2 in a leaf is low?

2. How do CAM plants solve the problem of obtaining CO2 for photosynthesis while minimizing water loss?

3. Describe the costs and benefits associated with the different nitrogen products excreted by fish, mammals and birds.

Answer 1

1) In hot dry conditions the photosynthetic efficiency of C3 plants suffer because of photorespiration. When CO2 in chloropasts drops below 50ppm , catalyst rubisco begins to fix oxygen instead of carbon.

2) CAM are C4 plants that fix CO2 during night. They store it as 4 C malate which releases CO2 during daylight when light dependent reaction of photosynthesis takes place.

Photorespiration is a wasteful pathway when occurs when calvin cycle rubisco acts on O2 . CAM plants minimize photorespiration and save water by seprating these steps in time, between day and night.

3) Urea is widely used in fertilizers as a convinent source of nitrogen.

Important raw material for chemical industry.