Citric Acid Cycle. The citric acid cycle is a series of reactions that produces two carbon dioxide molecules, one GTP/ATP, and reduced forms of NADH and FADH2.

These energy carriers join the 2 ATP and 2 NADH produced in glycolysis and the 2 NADH produced in the conversion of 2 pyruvates to 2 acetyl-CoA molecules. At the conclusion of the citric acid cycle, glucose is completely broken down, yet only four ATP have been produced.

After two rounds of the citric acid cycle, we have completely oxidized one molecule of glucose to CO 2​start subscript, 2, end subscript and captured its energy in a series of steps.

The TCA Cycle

• Step 1: Acetyl CoA (two carbon molecule) joins with oxaloacetate (4 carbon molecule) to form citrate (6 carbon molecule).
• Step 2: Citrate is converted to isocitrate (an isomer of citrate)
• Step 3: Isocitrate is oxidised to alpha-ketoglutarate (a five carbon molecule) which results in the release of carbon dioxide.

The function of the citric acid cycle is the harvesting of high-energy electrons from carbon fuels. Note that the citric acid cycle itself neither generates a large amount of ATP nor includes oxygen as a reactant (Figure 17.3).

The eight steps of the citric acid cycle are a series of redox, dehydration, hydration, and decarboxylation reactions. Each turn of the cycle forms one GTP or ATP as well as three NADH molecules and one FADH2 molecule, which will be used in further steps of cellular respiration to produce ATP for the cell.

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What would happen if NAD+ was not generated for the citric acid cycle? The pyruvate would be recycled back to glycolysis to form glucose again. Oxygen would accept the high-energy electrons and form water. The cycle would continue until NAD+ was available again.

FAD is flavin adenine dinucleotide, and NAD is nicotinamide adenine dinucleotide. FAD can accommodate two hydrogens whereas NAD accepts just one hydrogen. In NAD, a single hydrogen and an electron pair is transferred, and the second hydrogen is freed into the medium.

NAD+ is essential to the creation of energy in the body and the regulation of pivotal cellular processes. NAD+ has two general sets of reactions in the human body: helping turn nutrients into energy as a key player in metabolism and working as a helper molecule for proteins that regulate other cellular functions.

During the process of glycolysis, where the sugar glucose is broken down, energy is released in the form of electrons. In this reaction NAD+ accepts electrons and hydrogen, thus two molecules of NADH are formed for every one molecule of glucose.

Nicotinamide adenine dinucleotide (NAD+) and flavin adenine dinucleotide (FAD+) are two cofactors that are involved in cellular respiration. They are responsible for accepting “high energy” electrons and carrying them ultimately to the electron transport chain where they are used to synthesize ATP molecules.

The cellular respiration processes of all living cells make use of the coenzyme Nicotinamide adenine dinucleotide (NAD). It plays a key role in energy metabolism by accepting and donating electrons. The low energy form NAD+ shown at left is raised to the high energy form NADH.

Physical and chemical properties. Nicotinamide adenine dinucleotide consists of two nucleosides joined by pyrophosphate. The nucleosides each contain a ribose ring, one with adenine attached to the first carbon atom (the 1′ position) (adenosine diphosphate ribose) and the other with nicotinamide at this position.

Tips for increasing NAD+ levels naturally

1. Exercise. Exercise is one of the easiest ways to enhance your NAD+ levels and boost your overall health.
2. Limiting sun exposure. If you spend much time in the sun, you may be prematurely depleting your own supply of NAD+.
3. Seek the heat.
4. Dietary changes.
5. Fasting and ketosis diets.

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• Best Overall NR: Tru Niagen.
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• Best NR Powder: Botany Biosciences Nicotinamide Riboside Chloride.
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NAD and NADP are the most abundant coenzymes in the cells, which are used in oxidation-reduction reactions. Both NAD and NADP are structurally similar but, NADP contains a phosphate group. NAD is mainly used in the cellular respiration and electron transport chain whereas NADP is used in the photosynthesis.

Nicotinamide adenine dinucleotide (NAD) and its relative nicotinamide adenine dinucleotide phosphate (NADP) are two of the most important coenzymes in the cell. NADP is simply NAD with a third phosphate group attached as shown at the bottom of the figure.

After a photon hits the photosystem II (PSII) reaction center, energy from sunlight is used to extract electrons from water. The electrons travel through the chloroplast electron transport chain to photosystem I (PSI), which reduces NADP+ to NADPH (Figure 3).

The reduced NADP provides the reducing power (hydrogen) and is converted back to NADP which is then reduced again in the light-dependent reactions. ATP is also used to provide energy for the conversion. It is converted into ADP + Pi, which are reconverted into ATP in the light-dependent reactions.

Ferredoxin: NADP+ reductase is the last enzyme in the transfer of electrons during photosynthesis from photosystem I to NADPH. The NADPH is then used as a reducing equivalent in the reactions of the Calvin cycle.

What would you expect would happen if this chloroplast ran out of available NADP+? The organism would not be able to produce NADPH, but will be able to produce ATP.

The exergonic light-dependent reactions of photosynthesis convert light energy into chemical energy, producing ATP and NADPH. These reactions occur in the thylakoids of the chloroplasts. The products of the light-dependent reactions, ATP and NADPH, are both required for the endergonic light-independent reactions.

Photophosphorylation is the process of transferring the energy from light into chemicals, particularly ATP.

Answer: The important events of light reaction are (i) Excitation of chlorophyll molecule to emit a pair of electrons and use of their energy in the formation of ATP from ADP + Pi. This process is called photophosphorylation. Splitting of water molecule (a) (b) End products of light reaction are NADPH and ATP.