Final answer:
When an animal cannot access food, it first uses carbohydrates and fats for energy. Once these stores are depleted, it begins to break down proteins into amino acids for energy, leading to body wasting if starvation continues.
Step-by-step explanation:
When an animal is forced to survive without food for an extended period, it relies on different energy reserves before resorting to protein breakdown. Initially, the body uses carbohydrates and fat reserves for energy. As starvation continues and these reserves become depleted, the body then turns to proteins, breaking them down into amino acids which can be converted to ATP or utilized for glucose synthesis through gluconeogenesis. The prolonged breaking down of proteins for energy leads to a condition called body wasting, as it involves the breakdown of structural and functional tissues.
The first stage of energy utilization often involves carbohydrates, specifically glycogen stored in the liver and muscles. When glycogen stores are exhausted, the body switches to burning fatty acids and triglycerides to create ketone bodies, which serve as an alternative energy source. Only after depleting the glycogen and fat reserves does the body begin to break down proteins for energy, underlining the significance of carbohydrates and fats in the animal's bioenergetics.