Photosynthesis in Plants

The major process, that brings carbon form the atmosphere, into the living world is photosynthesis, where producers take in carbon dioxide from the atmosphere, and convert it into organic compounds. Oxygen is released as a by product. Carbon fixed by the producers, enters the food chain, and is passed to herbivores, carnivores and decomposers

Cyclic photophosphorylation involves only Photosystem I (PS I). Electrons cycle back to the reaction center, generating only ATP without the production of NADPH or oxygen.

Chlorophyll is a lipid-soluble pigment. It does not dissolve in water but is soluble in organic solvents like acetone, alcohol, or ether.

Leghemoglobin is an oxygen-binding protein found in the root nodules of leguminous plants. It maintains low oxygen levels to protect the oxygen-sensitive nitrogenase enzyme.

The chemical formula for chlorophyll b is C55H70O6N4Mg. It differs from chlorophyll a (C55H72O5N4Mg) by having an aldehyde group instead of a methyl group.

Chlorophyll a has a methyl (-CH3) group at the third carbon position, whereas chlorophyll b has an aldehyde (-CHO) group at that same position.

The action spectrum of photosynthesis shows that the highest rates of photosynthesis occur in the red and blue regions of the light spectrum, with red light being highly effective.

Non-cyclic photophosphorylation (Z-scheme) involves both Photosystem II and Photosystem I, resulting in the production of both ATP and NADPH.

Photosynthesis rate is influenced by light intensity, quality, and temperature. Duration of light (photoperiod) affects flowering but is not a direct factor in the immediate rate of photosynthesis.

In C3 photosynthesis, the first stable product of carbon fixation is 3-phosphoglyceric acid (3-PGA). It is formed when carbon dioxide reacts with ribulose-1,5-bisphosphate.

Photolysis of water (the splitting of water molecules) occurs in the lumen of the thylakoid and is associated with Photosystem II (PS II) to provide electrons for the electron transport chain.

The rate of translocation of organic solutes (photosynthates) in the phloem sieve tubes is generally accepted to be in the range of 50 to 100 cm/hour.

Quantosomes are considered the structural units of the thylakoid membrane, and it is widely cited in older botanical literature that a quantosome contains approximately 250 chlorophyll molecules.

Photorespiration occurs when the enzyme RuBisCO binds with oxygen instead of carbon dioxide. This process is favored under conditions of high oxygen concentration and low carbon dioxide concentration, often occurring in hot, dry environments.

Melvin Calvin and his colleagues used the unicellular green alga Chlorella in their pioneering experiments to map the carbon fixation pathway in photosynthesis.