How does nadh produce energy

Chemiosmosis Figure 4. The result of the reactions is the production of ATP from the energy of the electrons removed from hydrogen atoms. These atoms were originally part of a glucose molecule.

At the end of the electron transport system, the electrons are used to reduce an oxygen molecule to oxygen ions. The extra electrons on the oxygen ions attract hydrogen ions protons from the surrounding medium, and water is formed. The electron transport chain and the production of ATP through chemiosmosis are collectively called oxidative phosphorylation. The number of ATP molecules generated from the catabolism of glucose varies. For example, the number of hydrogen ions that the electron transport chain complexes can pump through the membrane varies between species.

Another source of variance stems from the shuttle of electrons across the mitochondrial membrane. The NADH generated from glycolysis cannot easily enter mitochondria. Another factor that affects the yield of ATP molecules generated from glucose is that intermediate compounds in these pathways are used for other purposes. Glucose catabolism connects with the pathways that build or break down all other biochemical compounds in cells, and the result is somewhat messier than the ideal situations described thus far.

For example, sugars other than glucose are fed into the glycolytic pathway for energy extraction. Other molecules that would otherwise be used to harvest energy in glycolysis or the citric acid cycle may be removed to form nucleic acids, amino acids, lipids, or other compounds. Overall, in living systems, these pathways of glucose catabolism extract about 34 percent of the energy contained in glucose. What happens when the critical reactions of cellular respiration do not proceed correctly?

Mitochondrial diseases are genetic disorders of metabolism. Mitochondrial disorders can arise from mutations in nuclear or mitochondrial DNA, and they result in the production of less energy than is normal in body cells. Symptoms of mitochondrial diseases can include muscle weakness, lack of coordination, stroke-like episodes, and loss of vision and hearing.

Most affected people are diagnosed in childhood, although there are some adult-onset diseases. Identifying and treating mitochondrial disorders is a specialized medical field. The educational preparation for this profession requires a college education, followed by medical school with a specialization in medical genetics. Medical geneticists can be board certified by the American Board of Medical Genetics and go on to become associated with professional organizations devoted to the study of mitochondrial disease, such as the Mitochondrial Medicine Society and the Society for Inherited Metabolic Disease.

The citric acid cycle is a series of chemical reactions that removes high-energy electrons and uses them in the electron transport chain to generate ATP. One molecule of ATP or an equivalent is produced per each turn of the cycle. The electron transport chain is the portion of aerobic respiration that uses free oxygen as the final electron acceptor for electrons removed from the intermediate compounds in glucose catabolism.

These two forms of NAD are known as a "redox couple," a term that is used to describe a reduced the "red" in redox and oxidized the "ox" in redox form of the same atom or molecule.

The term "oxidized" can be misleading, though, as it does not necessarily require oxygen. Redox reactions involve the gaining or loss of electrons. Meanwhile, if something is reduced, it is gaining electrons. The term "oxidized" has been adopted through history, originating from experiments in the late 18th century. In fact, they can span everything from the rusting of iron to the formation of minerals.

The charge of a molecule informs how it interacts with other molecules. Scientists have yet to identify what the optimal ratio is, let alone what the ramifications are when it's perturbed. This is because the ratio dictates how effectively the cell can produce ATP, adenosine triphosphate — the energy currency of the cell.

The food you consume goes through three phases to become energy: glycolysis, the Krebs Cycle, and the electron transport chain. Coupled reactions are frequently used in the body to drive important biochemical processes. Separate chemical reactions may be added together to form a net reaction. The free-energy change D G for the net reaction is given by the sum of the free-energy changes for the individual reactions.

For example, the phosphorylation of glycerol is a necessary step in forming the phospholipids that comprise cell membranes. Recall from the experiment, "Membranes and Proteins: Dialysis, Detergents, and Proton Gradients," that the phospholipids that form cell membranes are formed from glycerol with a phosphate group and two fatty-acid chains attached. This step actually consists of two reactions: 1 the phosphorylation of glycerol, and 2 the dephosphorylation of ATP the free-energy-currency molecule.

The reactions may be added as shown in Equations , below:. ATP is the most important "free-energy-currency" molecule in living organisms see Figure 2, below. Adenosine triphosphate ATP is a useful free-energy currency because the dephosphorylation reaction is very spontaneous; i. Thus, the dephosphorylation reaction of ATP to ADP and inorganic phosphate Equation 3 is often coupled with nonspontaneous reactions e. The body's use of ATP as a free-energy currency is a very effective strategy to cause vital nonspontaneous reactions to occur.

The removal of one phosphate group green from ATP requires the breaking of a bond blue and results in a large release of free energy. Removal of this phosphate group green results in ADP, adenosine diphosphate. As these coupled reactions e. In a typical cell, an ATP molecule is used within a minute of its formation. During strenuous exercise, the rate of utilization of ATP is even higher. Hence, the supply of ATP must be regenerated.

We consume food to provide energy for the body, but the majority of the energy in food is not in the form of ATP. The body utilizes energy from other nutrients in the diet to produce ATP through oxidation-reduction reactions Figure 3. This flowchart shows that the energy used by the body for its many activities ultimately comes from the chemical energy in our food. These reducing agents are then used to make ATP. ATP stores chemical energy, so that it is available to the body in a readily accessible form.

To make ATP, energy must be absorbed. One of the principal energy-yielding nutrients in our diet is glucose see structure in Table 1 in the blue box below , a simple six-carbon sugar that can be broken down by the body. When the chemical bonds in glucose are broken, free energy is released.

The complete breakdown of glucose into CO 2 occurs in two processes: glycolysis and the citric-acid cycle. The reactions for these two processes are shown in the blue box below.

The first process in the breakdown of glucose is glycolysis Equation 5 , in which glucose is broken down into two three-carbon molecules known as pyruvate. The pyruvate is then converted to acetyl CoA acetyl coenzyme A and carbon dioxide in an intermediate step Equation 6. In the second process, known as the citric-acid cycle Equation 7 , the three-carbon molecules are further broken down into carbon dioxide.

The energy released by the breakdown of glucose red can be used to phosphorylate add a phosphate group to ADP, forming ATP green. The net reactions for glycolysis Equation 5 and the citric-acid cycle Equation 7 are shown below.

Note: In the equations below, glucose and the carbon compounds into which glucose is broken are shown in red; energy-currency molecules are shown in green, and reducing agents used in the synthesis of ATP are shown in blue.

Note: Carbon atoms from glucose are shown in red. Coenzyme A is shown in purple. Note: The part of the molecule that participates in oxidation-reduction reactions is shown in blue. This table shows the two-dimensional representations of several important molecules in Equations This yield is far below the amount needed by the body for normal functioning, and in fact is far below the actual ATP yield for glucose in aerobic organisms organisms that use molecular oxygen.

For each glucose molecule the body processes, the body actually gains approximately 30 ATP molecules! See Figure 4, below. So, how does the body generate ATP? The process that accounts for the high ATP yield is known as oxidative phosphorylation.

These products are molecules that are oxidized i. As you will see later in this tutorial, it is the free energy from these redox reactions that is used to drive the production of ATP. This flowchart shows the major steps involved in breaking down glucose from the diet and converting its chemical energy to the chemical energy in the phosphate bonds of ATP, in aerobic oxygen-using organisms. Note: In this flowchart, red denotes a source of carbon atoms originally from glucose , green denotes energy-currency molecules, and blue denotes the reducing agents that can be oxidized spontaneously.

In the discussion above, we see that glucose by itself generates only a tiny amount of ATP. How does this work? As discussed in an earlier section about coupling reactions, ATP is used as free-energy currency by coupling its spontaneous dephosphorylation Equation 3 with a nonspontaneous biochemical reaction to give a net release of free energy i.

This set of coupled reactions is so important that it has been given a special name: oxidative phosphorylation. In addition, we must consider the reduction reaction gaining of electrons that accompanies the oxidation of NADH.

Oxidation reactions are always accompanied by reduction reactions, because an electron given up by one group must be accepted by another group. In this case, molecular oxygen O 2 is the electron acceptor, and the oxygen is reduced to water Equation 10, below. The molecular changes that occur upon oxidation are shown in red.

In this tutorial, we have seen that nonspontaneous reactions in the body occur by coupling them with a very spontaneous reaction usually the ATP reaction shown in Equation 3. But we have not yet answered the question: by what mechanism are these reactions coupled?

Every day your body carries out many nonspontaneous reactions. As discussed earlier, if a nonspontaneous reaction is coupled to a spontaneous reaction, as long as the sum of the free energies for the two reactions is negative, the coupled reactions will occur spontaneously. How is this coupling achieved in the body? Living systems couple reactions in several ways, but the most common method of coupling reactions is to carry out both reactions on the same enzyme.

Consider again the phosphorylation of glycerol Equations Glycerol is phosphorylated by the enzyme glycerol kinase, which is found in your liver. The product of glycerol phosporylation, glycerolphosphate Equation 2 , is used in the synthesis of phospholipids.

Glycerol kinase is a large protein comprised of about amino acids. X-ray crystallography of the protein shows us that there is a deep groove or cleft in the protein where glycerol and ATP attach see Figure 6, below.

Because the enzyme holds the ATP and the glycerol in place, the phosphate can be transferred directly from the ATP to glycerol. Instead of two separate reactions where ATP loses a phosphate Equation 3 and glycerol picks up a phosphate Equation 2 , the enzyme allows the phosphate to move directly from ATP to glycerol Equation 4.

The coupling in oxidative phosphorylation uses a more complicated and amazing! This is a schematic representation of ATP and glycerol bound attached to glycerol kinase. The enzyme glycerol kinase is a dimer consists of two identical subuits. There is a deep cleft between the subunits where ATP and glycerol bind.