5. Most dietary lipids are stored in adipose tissue; only a small portion is used for synthesis reactions. Adipocytes obtain lipids from chylomicrons, from VLDLs, and from their own synthesis reactions. 6. Many absorbed amino acids that enter hepatocytes are deaminated and can enter the Krebs cycle for ATP production or be used to synthesize glucose or fatty acids.
7. Some amino acids that enter hepatocytes are used to synthesize proteins.
8. Amino acids not taken up by hepatocytes are used in other body cells (such as muscle cells) for synthesis of proteins or regulatory chemicals such as hormones or enzymes.
Regulation of Metabolism during the Absorptive State
Soon after a meal, certain chemicals plus rising levels of blood glucose stimulate pancreatic beta cells to release Insulin . In general, insulin increases the activity of enzymes needed for anabolism and synthesis of storage molecules; at the same time, it decreases the activity of enzymes needed for catabolic or breakdown reactions. Insulin promotes the entry of glucose and amino acids into cells of many tissues, and it stimulates the phosphorylation of glucose in hepatocytes. In the liver and adipose tissue, insulin enhances the synthesis of triglycerides, and in cells throughout the body insulin stimulates protein synthesis.
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