NADP+ Definition

NADP+ is a coenzyme that functions as a universal electron carrier, accepting electrons and hydrogen atoms to form NADPH, or nicotinamide adenine dinucleotide phosphate. NADP+ is created in anabolic reactions, or reaction that build large molecules from small molecules. NADPH donates the hydrogen (H) and associated electrons, oxidizing the molecule to create NADP+. This molecule is typically at a lower concentration than its counterpart NADPH, which favors the release of the hydrogen and electron from NADPH.

Function of NADP

NADP+ functions alongside many enzymes to provide energy to the many reactions in a cell. NADP+ is the used form of NADPH, and must be reduced with more electrons and a hydrogen. This is typically done during photosynthesis in plants, or as part of sugar digestion in animals. The release of energy from the bonds of sugar, or the input of energy from the sun, allows the cells of these organisms to bind hydrogen with two electrons to NADP+, creating NADPH which can move this energy, electrons, and hydrogen to a new reaction within the cell.

  • NADPH – The reduced version of NADP+, which serves as a proton donor and electron carrier.
  • NADH – NADPH without an extra phosphate group, used mostly in catabolic reactions.
  • Electron Carrier – A molecule used to transfer electrons to various reactions and enzymes.


1. Glucose 6-phosphate dehydrogenase (G6PD) is an enzyme that is part of the process of breaking down glucose, a simple sugar. When G6PD works, it removes two hydrogens and two electrons from glucose 6-phosphate, and must give them to the coenzyme NADP+. Which of the following shows the correct reaction?
A. G6PD + Glucose 6-phosphate = G6PD + 6-Phospho-glucono-lactone
B. G6PD + NADP+ + Glucose 6-phosphate = G6PD + 6-Phospho-glucono-lactone + NADPH + H+
C. G6PD + NADP+ + Glucose 6-phosphate = G6PD + 6-Phospho-glucono-lactone + NADPH

Answer to Question #1
B is correct. When G6PD removes the hydrogens and electrons from the glucose, they must go somewhere. NADP+ will be able to accept one hydrogen and two electrons, or (H). Together, these will create the electrically neutral molecule NADPH. There remains a hydrogen with no electrons, or a free proton.