Photosynthesis and Carbohydrate Synthesis in Plants
Photophosphorylation is the process of using light energy to phosphorylate ADP and
generate ATP.
Photophosphorylation is compared to oxidative phosphorylation, which involves the
transfer of electrons from reduced cofactors to oxygen.
Photosynthesis is the process in which carbon dioxide is reduced by water, with water
serving as the electron donor.
The Calvin cycle, or dark reactions, use the energy from light reactions to reduce carbon
dioxide.
Light reactions, or photo-phosphorylation, convert light energy into chemical energy.
Electrons from reduced cofactors like NADH and FADH2 are passed to proteins in the
respiratory chain to oxygen in oxidative phosphorylation.
In photophosphorylation, water is the source of electrons that are transported to NADP+
and light energy is used to generate NADPH and phosphorylate ADP.
NADH is an excellent electron donor and undergoes electron transfer and proton pumping
in the electron transport chain.
ATP synthesis in both oxidative phosphorylation and photophosphorylation is driven by the
electrochemical potential generated by proton pumping.
The chemiosmotic model explains ATP synthesis through the movement of protons
through a membrane-bound ATP synthase.
Photophosphorylation takes place in chloroplasts, while oxidative phosphorylation occurs
in mitochondria.
The chemiosmotic mechanism for ATP synthesis is present in both chloroplasts and
mitochondria.
Light and dark reactions occur in chloroplasts, which have an outer permeable membrane
and an inner impermeable membrane.
The overall reaction for electron flow in chloroplasts, known as Hill's reaction, involves the
production of NADPH, protons, and oxygen.
Light absorption in photosynthesis involves the lifting of an electron to a higher energy
level, followed by its rapid return to a lower-energy orbital.
Excitation energy in photosynthesis is transferred to neighboring molecules to drive
chemical reactions.
Light Harvesting and Photosynthetic Pigments
Chlorophyll a and b are primary photosynthetic pigments that absorb light due to their