Biochemistry, 4th Edition P90. Continuing Garrett and Grisham's innovative conceptual and organizing framework, "Essential Questions," BIOCHEMISTRY guides students through course concepts in a way that reveals the beauty and usefulness of biochemistry in the everyday world. Streamlined for increased clarity and readability, this edition also includes new photos and illustrations that show the subject matter consistently throughout the text. New end-of-chapter problems, MCAT practice questions, and the unparalleled text/media integration with the power of CengageNOW round out this exceptional package, giving you the tools you need to both master course concepts and develop critical problem-solving skills you can draw upon. | What Regulates Our Eating Behavior 853 Glycogen I FIGURE Metabolic conversions of glucose-6-phosphate in the liver. brain and other tissues. If energy demands are low fatty acids are incorporated into triacylglycerols that are carried to adipose tissue for deposition as fat. Cholesterol is also synthesized in the liver from two-carbon units derived from acetyl-CoA. In addition to these central functions in carbohydrate and fat-based energy metabolism the liver serves other purposes. For example the liver can use amino acids as metabolic fuels. Amino acids are first converted to their corresponding a-keto acids by aminotransferases. The amino group is excreted after incorporation into urea in the urea cycle. The carbon skeletons of glucogenic amino acids can be used for glucose synthesis whereas those of ketogenic amino acids appear in ketone bodies see Figure . The liver is also the principal detoxification organ in the body. The endoplasmic reticulum of liver cells is rich in enzymes that convert biologically active substances such as hormones poisons and drugs into less harmful by-products. Liver disease leads to serious metabolic derangements particularly in amino acid metabolism. In cirrhosis the liver becomes defective in converting NH4 to urea for excretion and blood levels of NH4 rise. Ammonia is toxic to the central nervous system and coma ensues. What Regulates Our Eating Behavior Approximately 65 of Americans are overweight and one in three Americans is clinically obese overweight by 20 or more . Obesity is the single most important cause of type 2 adult-onset insulin-independent diabetes. Research into the regulatory controls that govern our feeding behavior has become a medical urgency with great financial incentives given the epidemic proportions of obesity and widespread preoccupation with dieting and weight loss. The Hormones That Control Eating Behavior Come From Many Different Tissues Appetite and weight regulation are .
