Chapter 24 Metabolic Pathways for Lipids and Amino Acids Lecture Presentation Chapter 24 Metabolic Pathways for Lipids and Amino Acids Karen C. Timberlake

Chapter 24 Metabolic Pathways for Lipids and Amino Acids Patients diagnosed with chronic hepatitis C virus (HCV) infection require lifelong monitoring by a specialist team including a public health nurse. A public health nurse works in public health departments, correctional facilities, occupational health facilities, schools, and organizations that aim to improve health at the community level.

Chapter 24 Readiness Core Chemistry Skills Identifying Fatty Acids (17.2) Drawing the Zwitterion for an Amino Acid (19.1) Identifying Important Coenzymes in Metabolism (22.3) Identifying the Compounds in Glycolysis (22.4) Identifying the Compounds and Enzymes in Glycogenesis and Glycogenolysis (22.6) Describing the Reactions in the Citric Acid Cycle (23.1) Calculating the ATP Produced from Glucose (23.3)

24.1 Digestion of Triacylglycerols The fat cells (adipocytes) that make up adipose tissue are capable of storing unlimited quantities of triacylglycerols. Adipose tissue (made of adipocytes) stores 85% of the total energy available in the body. Learning Goal Describe the sites of and products obtained from the digestion of triacylglycerols.

Digestion of Triacylglycerols In the digestion of fats (triacylglycerols), bile salts break fat globules into smaller particles called micelles in the small intestine. pancreatic lipases hydrolyze ester bonds to form monoacylglycerols and fatty acids, which recombine in the intestinal lining. phospholipids and proteins coat the fats, forming chylomicrons, which are transported to the cells of heart, muscle, and adipose tissues. lipases hydrolyze triacylglycerols, forming glycerol and free fatty acids, which are oxidized to acetyl CoA molecules for ATP synthesis.

Digestion of Triacylglycerols The digestion of fats begins in the small intestine when bile salts emulsify fats that undergo hydrolysis to monoacylglycerols and fatty acids.

Utilization of Fat When blood glucose is depleted and glycogen stores are low, the process of fat utilization is stimulated. the hormones glucagon or epinephrine are secreted into the bloodstream, where they bind to receptors on the membrane of adipose tissue. a hormone-sensitive lipase within the fat cells catalyzes the hydrolysis of triacylglycerols to glycerol and free fatty acids. glycerol and fatty acids diffuse into the bloodstream and bind with plasma proteins to be transported to the tissues, muscles, and fat cells.

Metabolism of Glycerol Glycerol from fat digestion adds a phosphate from ATP to form glycerol-3-phosphate. undergoes oxidation of the —OH group to dihydroxyacetone phosphate. becomes an intermediate in glycolysis and gluconeogenesis.

Metabolism of Glycerol

Study Check Give answers for the following questions about fat digestion: 1. What is the function of bile salts in fat digestion? 2. How is glycerol utilized?

Solution Give answers for the following questions about fat digestion: 1. What is the function of bile salts in fat digestion? Bile salts break down fat globules, allowing pancreatic lipases to hydrolyze the triacylglycerol. 2. How is glycerol utilized? Glycerol adds a phosphate and is oxidized to an intermediate of the glycolysis and gluconeogenesis pathways.