Question

Describe the events of the absorptive state. Include chemical messengers as you describe the events that accompany that state. Use your vocabulary for any anabolic or catabolic activities associated with this state that apply to sources of energy. When is the body in the absorptive state?

Answer 1

Absorptive or fed condition occurs after a meal when the body digests food and consumes nutrients (catabolism exceeds anabolism). Digestion starts when you place food in your mouth, as the food is broken down into its constituent parts to be consumed through the intestine.

Digestion of carbohydrates starts in the mouth while digestion of protein and fat occurs in the stomach and small intestines. These components of carbohydrates, fats, and proteins pass through the intestinal wall and enter the bloodstream (sugars and amino acids) or lymphatic system (fats).

These systems carry them from the intestines into the liver, adipose tissue, or muscle cells which process and use or store energy. The absorptive state can linger for up to 4 hours depending on the amounts and types of nutrients ingested. Food intake and rising bloodstream glucose concentrations stimulate pancreatic beta cells to release insulin into the bloodstream, where it initiates the absorption of blood glucose by liver hepatocytes and adipose and muscle cells.

The glucose is immediately converted into glucose-6-phosphate once inside these cells. In doing so, a concentration gradient is formed in which blood glucose levels are higher than in cells. This helps glucose to pass from the blood to the cells where it is required.

insulin also encourages the production of glucose in the liver and muscle cells as glycogen, where it can be used for the body's later energy needs. Insulin can also stimulates protein synthesis in the body, too. As you'll see, in times of malnutrition muscle protein can be catabolized and used as fuel.

When energy is expended shortly after eating, the just-ingested dietary fats and sugars will be processed and then used for energy use. If not, excess glucose is retained in the liver and muscle cells as glycogen, or as fat in adipose tissue; excess dietary fat is also contained in adipose tissue as triglycerides.