For pyruvic acid to enter the citric acid cycle, it must first be oxidized to acetyl CoA. The acetyl CoA then joins with a molecule of oxaloacetic acid to form citric acid in the citric acid cycle. After one turn of the citric acid cycle, the citric acid regenerates the oxaloacetic acid molecule consumed. Many of the intermediates of the citric acid cycle are used for other purposes. Succinyl CoA, for example, is used in the production of heme, the iron-containing molecule in hemoglobin and in the cytochromes of electron transport. This use of citric acid cycle intermediates reduces the amount of oxaloacetic acid available to join with acetyl CoA. If acetyl CoA cannot enter the citric acid cycle, it is converted to ketone bodies that are eliminated in the urine. When oxaloacetic acid is low, an enzyme converts pyruvic acid to oxaloacetic acid. Dr. Atkins’ diet is a popular weight-loss program. The principle is for dieters to consume large quantities of fats and protein, but to avoid carbohydrates. How does this diet cause weight loss? Hint: Consider the steps of cellular respiration and think about what other molecules would be missing if there was no glucose to begin the process.

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Need by 12 tonight

posted 5 pm so need 6 hours from now. thank you.