23.3 ATP Energy from Glucose The malate–aspartate shuttle transfers the energy stored in NADH to transporters that move from the cytosol into the mitochondrial matrix, where NADH is regenerated for use in electron transport Learning Goal Account for the ATP produced by the complete oxidation of glucose.

ATP from Glycolysis The total ATP from complete oxidation of glucose is calculated by combining the ATP produced from glycolysis (glucose produces 7 ATP): five ATP from two NADH (malate–aspartate shuttle) and two ATP from direct phosphate transfer. the oxidation of pyruvate. the citric acid cycle. electron transport. In glycolysis, the oxidation of glucose stores energy in two NADH molecules and two ATP molecules from direct phosphate transfer.

Malate–Aspartate Shuttle Because glycolysis occurs in the cytosol, the NADH produced cannot pass through the mitochondrial inner membrane. the hydrogen ions and electrons from NADH can be moved in and out of the mitochondria by a transporter, the malate–aspartate shuttle. malate dehydrogenase catalyzes the reaction of oxaloacetate and NADH to yield malate and NAD+. a transporter binds the malate and carries it across the membrane into the matrix, where malate dehydrogenase oxidizes malate back to oxaloacetate.

Malate–Aspartate Shuttle, ATP The oxidation to oxaloacetate provides hydrogen ions and electrons that are used to reduce NAD+ to NADH, which can now enter electron transport to synthesize ATP.

Malate–Aspartate Shuttle, ATP Because the oxaloacetate produced in the matrix cannot cross the mitochondrial membrane, it is converted back to aspartate; moves out of the matrix back into the cytosol; and undergoes transamination, which converts it to oxaloacetate. The resulting NAD+ can participate again in glycolysis in the cytosol.

ATP from Oxidation of Pyruvate Under aerobic conditions, pyruvate enters the mitochondria. is oxidized to give acetyl CoA, CO2, and NADH. Because glucose yields two pyruvate, two NADH enter electron transport. their oxidation leads to the production of five ATP.

ATP from Citric Acid Cycle The two acetyl CoA produced from two pyruvate enter the citric acid cycle. Two acetyl CoA from one glucose produce a total of six NADH; two FADH2; and two ATP. In electron transport, six NADH produce 15 ATP, and two FADH2 produce 3 ATP.

ATP from Citric Acid Cycle In two turns of the citric acid cycle, a total of 20 ATP are produced. 6 NADH × 2.5 ATP/NADH = 15 ATP 2 FADH2 × 1.5 ATP/FADH2 = 3 ATP 2 GTP × 1 ATP/GTP = 2 ATP Total two turns = 20 ATP The overall equation for the reaction of two acetyl CoA is

ATP from Oxidation of Glucose Core Chemistry Skill Calculating the ATP Produced from Glucose

Complete Oxidation of Glucose The complete oxidation of glucose to CO2 and H2O yields a maximum of 32 ATP.

Chemistry Link to Health: Efficiency of ATP Production In a laboratory calorimeter, 1 mole of glucose produces 690 kcal. C6H12O6 + 6O2  6CO2 + 6H2O + 690 kcal To calculate the ATP energy produced in the mitochondria from glucose, we use the energy of the hydrolysis of ATP (7.3 kcal/mole of ATP).

Chemistry Link to Health: Efficiency of ATP Production Our cells are about 33% efficient in converting the total available chemical energy in glucose to ATP. The remainder of the energy produced from glucose during the oxidation in our cells is lost as heat.

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