In photosynthesis, carbon dioxide and water are used to produce glucose and the by-product oxygen, and there is an intake of energy. In respiration, on the other hand, glucose and oxygen are broken down into carbon dioxide and water, and there is a release of energy. Basically, the products of one serve as the reactants of the other, and vice versa.
As the name suggests, light-independent reactions do not need the presence of light to function. The process occurs in the stroma and it produces G3P, which is used for carbohydrates such as glucose. Light-dependent reactions, on the other hand, rely on the presence of light energy. The process occurs in the thylakoid and it produces ATP, NADPH, and oxygen as a by-product.
Chlorophyll contains a porphyrin ring that allows the free movement of electrons to easily gain or lose them. It is the most abundant pigment for photosynthesis as it absorbs light
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The electrons are then transferred to PSII. Photolysis provides energy in the form of electrons so that the PSII can continue to function which will later on lead to the production of NADPH. Also, photolysis provides protons which will later on lead to the production of ATP.
Protons are produced through photolysis in PSII and the cytochrome complex. 2 protons are released into the thylakoid space through the splitting of a hydrogen molecule. The cytochrome complex uses the energy it gains from the electrons from PSII to pump protons in the thylakoid space. This then creates a concentration gradient of protons in the thylakoid space.
Since protons are released through photolysis and are pumped in through the cytochrome complex, a concentration gradient is formed. To achieve equilibrium protons would tend to go out through the ATP synthase. The ATP synthase is then powered by the protons, which in turn, produces phosphate to combine with ADP to produce