Question

How would you explain the significance of NADPH in photosynthesis and NADH in cellular respiration?

Answer 1

Hint: NADPH stands for- Nicotinamide adenine dinucleotide phosphate and NADH stands for Nicotinamide adenine dinucleotide. They both act as electron donors and acceptors in the metabolism process of living organisms.

Complete answer:
Photosynthesis is a chemical process used by green plants and few other organisms to convert light energy into chemical energy. The sugar produced by this process is converted into ATP. Sunlight functions as the main source of light energy, while carbon dioxide and water are the main reactants. It is a redox mechanism where carbon dioxide is reduced to form sugar molecules, and water molecules are oxidized to form oxygen molecules. The molecular oxygen is released as a byproduct.

NADPH is an energy-carrying co-factor molecule that donates electrons and hydrogen atoms in enzyme-catalyzed reactions. The NADPH accepts high energy electrons in the process of photosynthesis and carries or transfers them to other molecules. It is produced in the first stage of photosynthesis by the addition of electrons. They help in the oxidation and reduction of substances during the process of photosynthesis by accepting or releasing electrons. They carry electrons and protons to form the carbon-carbon bonds in the sugar molecule.
NADPH produced during photosynthesis also provides the energy for the Calvin cycle in plants.

The set of chemical metabolic reactions that occur in living organisms to produce energy through the breakdown of food molecules or sugar molecules by the action of oxygen is called cellular respiration. The reactants of this reaction are- oxygen and glucose. ATP (Adenosine Triphosphate) and waste products like- carbon dioxide and water are the products obtained. These reactions begin in the cytoplasm of the cell and then proceed to the double-membranous organelle- Mitochondria. It occurs in the sets of three metabolic pathways- Glycolysis, Krebs cycle, and the electron transport chain reaction.

NADH is a naturally occurring biological cofactor. They play an important role in energy production and act as essential coenzymes during redox reactions in various metabolic processes. They donate electrons during the process of cellular respiration and helps in the oxidation of glucose. They accept the energized electrons and pass this energy to power the electron transport chain reaction. They donate hydrogen atoms in the process of cellular respiration for the formation of the water molecules. The proton gradient and electron transfer chain created by these molecules aid the process of cellular respiration that leads to the formation of energy molecules or ATP.

Note: In the reaction of photosynthesis, NADPH exist in two forms. NADP+ is the oxidized form, and NADPH is the reduced form. NADPH is formed during the photolysis of water, while NADP+ is formed during the synthesis of glucose.
In cellular respiration, NADH also exists in two forms. NAD+ is the oxidized form, and NADH is the reduced form. NAD+ accepts electrons from the food molecules to become NADH, which further donates electrons to the oxygen molecule.