Chapter 41 (5)

True or False:
The enerfy obtained from food balances the expenditure of energy for metabolism, activity, and storage.
True False

Nearly all of an animal's __ generation is based ont eh oxidation of energy rich organic molecules- carbs, proteins, fats- in cellular respiration.

Although any substances can be used as fuel, most animals "burn" proteins only after exhausting their supply of carbs and fats. __ are especially rich in energy; oxidizing a gram of fat liberates about twice the energy liberated from a gram of carbs or protein.

When an animal takes in more energy-rich molecules than it breaks down, the excessis converted to storage moleucles. In humans,t eh primary sites of storage are __ and __. Excess energy from the diet is stored there in the form oof __, a polymer made up of many glucose units. When fewer calories are taken in than are expended- perhaps because of sustained heavy exercise or lack of food- __ is oxidized. The hormones __ and __ maintain glucose homeostasis by tightly regulating glycogen synthesis and breakdown.

__ represent a secondary site of energy storage in the body. If glycogen depots are full and caloric intake exceeds caloric expenditure, the excess is usualyl stored as fat. When more energy is required than is generated from the diet, the human body generally expends liver glycogen first and tehn draws on muscle glycogen and fat. Most healthy people have enough stored fat to sustain them through several weeks without food.

__, the consumption of more calories than the body needs for normal metabolism, causes __, the excessive accumulation of fat. __, in turn, contributes to a number of health problems, including the most common type of diabetes (2), colon and breast cancer, and cardiovascular disease that leads to heart attacks and strokes.

Researchers have discovered several homeostatic mechanisms that help regulate body weight. Operateing as feedback circuits, these mechanisms control the storage and metabolism of fat. Several hormones regulate long-term and short-term appetite by affecting a "__" in the brain. A network of neurons relays and integrates info from the digestive system to regulate hormone release.

__ and the __ receptor are key components of the circuittry that regulates appetite over teh long term. __ is a product of adipose cells, so levels rise when body fat increases, cuing the brain to suppress appetite. Conversely, loss of fat decreases __ levels, signaling the brain to increase appetite. In this way, the feedback signals provided by __ maintain body fat levels within a set range.