Answer the following question given this paragraph: 

Many important biological processes involve redox reactions, which frequently store and release energy. For example, photosynthesis involves the reduction of carbon dioxide into glucose and the oxidation of water into oxygen. This process stores the energy of sunlight in the bonds of sugars. The reverse reaction, cellular respiration, converts the energy in glucose into ATP. Cellular respiration involves the oxidation of glucose to carbon dioxide and the reduction of oxygen gas to water. This process depends on the reduction of NAD + to the electron carrier NADH, and the reverse oxidation of NADH to NAD + . The reduction of NAD + leads to the formation of a proton (H + ) gradient, which drives the synthesis of ATP. NADH (nicotinamide adenine dinucleotide) and NADPH (Nicotinamide adenine dinucleotide phosphate) are electron carriers in biological systems. The term redox state is often used to describe the balance between NAD + /NADH and NADP + /NADPH (Nicotinamide adenine dinucleotide phosphate).


Q: What reaction is considered the reverse of photosynthesis?


A:
cellular respiration