Question

describe how in photosynthesis light energy is converted into chemical energy in the form of ATP

(For *8 marks)

Answer 1

During the process of photosynthesis, light penetrates the cell and passes into the chloroplast. The light energy is intercepted by chlorophyll molecules on the granal stacks. Some of the light energy is converted to chemical energy. During this process, a phosphate is added to a molecule to cause the formation of ATP. The third phosphate chemical bond contains the new chemical energy. The ATP then provides energy to some of the other photosynthetic reactions that are causing the conversion of CO2 into sugars. 

While the above reactions are proceeding CO2 is diffusing into the chloroplast. In the presence of the enzyme Rubisco, one molecule of CO2 is combined with one molecule of RuBP, and the first product of this reaction is two molecules of PGA. 

The PGA then participates in a cycle of reactions that result in the production of the sugars and in the regeneration of RuBP. The RuBP is then available to accept another molecule of CO2 and to make more PGA.