The reactions you've provided represent key processes in the energy cycle of living organisms, specifically photosynthesis and cellular respiration. Here’s a breakdown of each:
a. Photosynthesis: \[ 6 \text{CO}_2 + 6 \text{H}_2\text{O} + \text{sunlight} \rightarrow \text{C}6\text{H}{12}\text{O}_6 + 6 \text{O}_2 \] This reaction shows how plants use carbon dioxide and water, in the presence of sunlight, to produce glucose (C6H12O6) and oxygen. This process occurs in the chloroplasts of plant cells and is essential for producing the organic compounds that form the basis of the food chain.
b. Cellular Respiration: \[ \text{C}6\text{H}{12}\text{O}_6 + \text{O}_2 \rightarrow 6 \text{CO}_2 + 6 \text{H}_2\text{O} + \text{energy} \] This reaction describes cellular respiration, where glucose is broken down with the help of oxygen to produce carbon dioxide, water, and energy (in the form of ATP). This process occurs in the mitochondria of both plant and animal cells and is how organisms convert the chemical energy stored in food into usable energy.
c. Photosynthesis (reversed): \[ 6 \text{CO}_2 + 6 \text{H}_2\text{O} + \text{sunlight} \rightarrow \text{C}6\text{H}{12}\text{O}_6 + 6 \text{O}_2 \] This is essentially the same as the first equation (a). It depicts the same process of photosynthesis and is sometimes written in reverse to emphasize how the products of one process are the reactants of the other.
In summary, reactions (a) and (c) represent photosynthesis, while (b) represents cellular respiration. These processes are interconnected, with photosynthesis producing glucose and oxygen, which are then used in cellular respiration to generate energy.