Which of the following is true about plants and cellular energy?

Question

A.
Plants use light energy to produce food molecules during cellular respiration and to obtain cellular energy from the bonds of these food molecules during photosynthesis.
B.
Plants use light energy to produce food molecules during photosynthesis and obtain cellular energy from the bonds of these food molecules during cellular respiration.
C.
Plants can use light energy to produce food molecules or to obtain cellular energy from the bonds of these food molecules during cellular respiration.
D.
Plants can use light energy to produce food molecules or to obtain cellular energy from the bonds of these food molecules during photosynthesis.

Answer 1

A few concepts to understand:

 

1. Food is complex molecules (with lots of bonds) that store energy. Therefore if you are making it (building bonds), you have to put in energy and if you are breaking it down (destroying bonds), you get energy out. 

 

2. Photosynthesis is the process by which plants synthesize food using energy from light (photo-) 

 

3. Respiration is the process by which all organisms break down food to obtain energy. 

 

#2 and #3 are separate processes that can be linked together to convert energy from light in plants:

 

light energy -> stored energy (food) -> released energy 

 

Therefore, based on these concepts, the answer is B, plants use light energy to produce food during photosynthesis and obtain cellular energy from the bonds of these food molecules during respiration.