NAD+ accepts electrons and hydrogen during the processes of glycolysis, pyruvate oxidation and the citric acid cycle as well as the breakdown of fatty acids. NADH is used to make ATP (energy) by giving Complex I of the ETC in the mitochondria the electrons and hydrogen it has collected.
How the NAD+ and NADH Help Create Cellular Energy (And More) The conversion of NAD+ to NADH, and vice versa, are essential reactions in creating ATP during what's called cellular respiration. The food you consume goes through three phases to become energy: glycolysis, the Krebs Cycle, and the electron transport chain.
This methylation system is quantitatively by far the predominant NAM scavenging pathway under most conditions. While an acute pharmacological dose of NAM can be converted by CYP2E1 to nicotinamide N-oxide, which is then excreted to the urine.
Nicotinamide adenine dinucleotide (NAD) is a vital cofactor involved in brain bioenergetics for metabolism and ATP production, the energy currency of the brain (Lautrup et al., 2019).
These carriers take the electrons from NADH and FADH2, pass them down the chain of complexes and electron carriers, and ultimately produce ATP. More specifically, the electron transport chain takes the energy from the electrons on NADH and FADH2 to pump protons (H+) into the intermembrane space.
The NAD+ is a coenzyme nicotinamide adenine dinucleotide, which acts as an electron acceptor in the process of glycolysis and Krebs cycle.
NADH and FADH2 molecules formed during Glycolysis and Krebs Cycle carry their electrons to the electron transport chain. The electron transport chain creates a proton gradient that ultimately leads to the production of a large amount of ATP.
Under aerobic conditions, NAD is regenerated when the electrons from NADH molecules are shuttled into the mitochondria and the electron transport chain. The electrons from NADH eventually make their way to molecular oxygen, which is reduced to water.
NAD+ is known to restore healthy concentrations of ATP in cells. This is particularly interesting in studies of Mitochondrial DNA Depletion Syndromes, characterized by reductions in mitochondrial DNA and ATP production. Liver failure usually leads to death in infancy in these rare disorders.
NAD+ to NADH transformation
When NAD+ takes an electron from glucose, it becomes NADH, the reduced form of the molecule. NADH transports this electron to mitochondria where the cell can take the energy that is stored in the electron. NADH then donates the electron to oxygen, converting it back to NAD+.
NAD+ is mostly used in catabolic pathways, such as glycolysis, that break down energy molecules to produce ATP. The ratio of NAD+ to NADH is kept very high in the cell, keeping it readily available to act as an oxidizing agent. NADH is used in the electron transport chain to provide energetic electrons.
The cofactor is, therefore, found in two forms in cells: NAD+ is an oxidizing agent – it accepts electrons from other molecules and becomes reduced. This reaction, also with H+, forms NADH, which can then be used as a reducing agent to donate electrons.
NAD can become REDUCED to NADH2, and then carry the electrons to some other reaction and become OXIDIZED back to NAD. In other words, NAD can pick up electrons from one reaction and carry them to another. Note that when a molecule gets OXIDIZED IT LOSES ENERGY.
NAD+ becomes NADH when two electrons and a hydrogen are added to the molecule. One molecule of glucose can form 10 molecules NADH. NAD+ accepts electrons and hydrogen during the processes of glycolysis, pyruvate oxidation and the citric acid cycle as well as the breakdown of fatty acids.
How does NAD+ differ from NADH? NAD+ can store 2 electrons and a hydrogen proton to become NADH. NADH represents stored energy.
The reactants are pyruvate, NADH, and a proton. The products are lactate and NAD+. The process of fermentation results in the reduction of pyruvate to form lactic acid and the oxidation of NADH to form NAD+. Electrons from NADH and a proton are used to reduce pyruvate into lactate.
In alcohol fermentation, NAD+ is regenerated from NADH through the reduction of acetaldehyde to ethanol (ethyl alcohol).
During glycolysis, one glucose molecule is converted to two pyruvate molecules, producing two net ATP and two NADH. During NADH regeneration, the two NADH donate electrons and hydrogen atoms to the two pyruvate molecules, producing two lactate molecules and regenerating NAD+.
The process of forming ATP from the electron transport chain is known as oxidative phosphorylation. Electrons carried by NADH + H+ and FADH2 are transferred to oxygen via a series of electron carriers, and ATPs are formed. Three ATPs are formed from each NADH + H+, and two ATPs are formed for each FADH2 in eukaryotes.
The oxidation of one molecule of NADH thus leads to the synthesis of three molecules of ATP, whereas the oxidation of FADH2, which enters the electron transport chain at complex II, yields only two ATP molecules.
Oxidation of one molecule of NADH in the ETS gives rise to 3 molecules of ATP by oxidative phosphorylation and FADH2 produces 2 ATP molecules theoretically.
High-energy electrons are released from NADH and FADH2, and they move along electron transport chains, like those used in photosynthesis. The electron transport chains are on the inner membrane of the mitochondrion. As the high-energy electrons are transported along the chains, some of their energy is captured.
As electrons move through the electron transport chain, they go from a higher to a lower energy level and are ultimately passed to oxygen (forming water). Energy released in the electron transport chain is captured as a proton gradient, which powers production of ATP by a membrane protein called ATP synthase.
NADH is the electron donor in this system. It initiates the electron transport chain by donating electrons to NADH dehydrogenase (blue). NADH donates two electrons to NADH dehydrogenase. At the same time, the complex also pumps two protons from the matrix space of the mitochondria into the intermembrane space.