Tag: emerson's experiments & hill's reaction

Light phase is also known as a photochemical phase because it is a light dependent phase. During this phase, the formation of high-energy chemical intermediates ATP and NADPH$ _{2}$ takes place. ATP and NADPH$ _{2}$ are the assimilatory power of photosynthesis. Light phase also includes light absorption, water splitting and release of oxygen. Two photosynthetic units called Photosystem I and Photosystem II are also involved in light phase. Light phase consists of two photochemical reactions, i.e. non-cyclic photophosphorylation and cyclic photophosphorylation.

In photosynthesis, the light-dependent reactions take place on the thylakoid membranes. The light-independent reactions take place in the stroma. The thylakoid membrane contains some integral membrane protein complexes that catalyze the light reactions. There are four major protein complexes in the thylakoid membrane Photosystem II (PSII), Cytochrome b6f complex, Photosystem I (PSI), and ATP synthase. These four complexes work together to ultimately create the products ATP and NADPH.

Light reactions of photosynthesis which takes place in thylakoids membranes of chloroplast utilize sunlight and water to produce oxygen, ATP and NADPH.

Photosynthesis is a process in which phosphorylation occurs. Phosphorylation is a process in which phosphate group is added, and in the case of photosynthesis it happens in the presence of light, thus called as 'photophosphorylation'. ADP is converted to ATP, the energy currency as the main product of this process. In photosynthesis, cyclic and non-cyclic photophosphorylation takes place in the light phase and generate ATP and NADPH.

Photoluminescence is the phenomenon of light emission after absorption of photons in the form of electromagnetic radiation. Chemiluminescence is the phenomenon of emission of light from a chemical reaction. Phosphorescence is a type of photoluminescence which is related to fluorescence. It does not re-irradiate the absorbed light immediately like fluorescence. Fluorescence is the phenomenon of re-irradiation of light absorbed light or electromagnetic radiation.

A) ADP and ${ H } _{ 2 }O$ are required in addition to NADP.

The process that converts light energy into chemical energy takes place in a multi-protein complex called a photosystem. Two types of photosystems are embedded in the thylakoid membrane:- photosystem II ( PSII) and photosystem I (PSI). Each photosystem plays a key role in capturing the energy from sunlight by exciting electrons. These energized electrons are transported by “energy carrier” molecules, which power the light-independent reactions.

The first and foremost step of photosynthesis is the excitation of chlorophyll molecule which occurs with the absorption of light. This reaction is photochemical reaction since involves light and results in chemical change by transfer of electrons. The pigments present in the photosystems absorb photon of light. The photons excite electrons in the chlorophyll which then move through the electron transport chain and results in the production of carbohydrates and energy packets NADPH, ATP with the release of oxygen.

The Hill reaction implies that the light-dependent reaction of photosynthesis is a result of a series of redox reactions and a suitable terminal electron acceptor is required for that reaction to occur. Hence, solar energy is converted to chemical energy by the reduction of NADP to NADPH.