Question

Calculate the rate of photosynthesis (mm/hr) for Elodea if when measuring net photosynthesis, the water level moved up 4mm from the initial level in 10 min, and when measuring cellular respiration it took 20 minutes for the water level to move down 1 mm. 021 mm/hr 0 15 mm/hr 25 mm/hr O 30 mm/hr 27 mm/hr 5

Answer 1

Ans: Photosynthesis is the conversion of light energy to chemical energy in the form of reducing power (NADPH) and ATP and use them to derive CO2 fixation.

Net reaction: 6CO2+ 6H2O------> C6H12O6+ O2.

Cellular respiration is the process of producing ATP molecules by using Glucose and oxygen. So if we thin we can say that photosynthesis is the process of producing the glucose and cellular respiration is the process of breaking the glucose and oxygen for the generation of ATP molecules. So we can say that photosynthesis and cellular respiration is opposite to each other.

Now in the question it is given that during net photosynthesis water level increases to 4mm from reference point in 10 minutes so its rate is 4*60/10 mm/hr= 24 mm/hr (4-0/10 mm/hr), for cellular respiration its rate is 3*60/20 mm/hr= 9 mm/hr because water level is decreasing from 4 mm to 1 mm in 20 minute (4-1/20 mm/hr).

So Rate of photosyntheis= Rate of net photosyntheis- Rate of cellular respiration (since these two reactions are opposite to each other). 24 mm/hr-9 mm/hr= 15 mm/hr which is less than the net rate of photosynthesis because some of the produced energy in photosynthesis is used in cellular respiration.

So option (b) 15 mm/hr is the right answer.