During hibernation (in animals like the brown bear), after the body’s supply of carbohydrates and excess polypeptides have been used for energy, the hibernating animal must switch to using:
A. amylopectin (a storage form of polysaccharides)
B. protein (a storage form of amino acids)
C. glycogen (a storage form of polysaccharides)
D. fat (a storage form of triglycerides)
E. amylose (a storage form of polysaccharides)
The correct answer and explanation is:
The correct answer is D. fat (a storage form of triglycerides).
During hibernation, animals like the brown bear enter a state of metabolic dormancy, where they significantly reduce their activity levels and rely on stored energy reserves to sustain essential physiological functions. In the initial phase of hibernation, the body primarily utilizes carbohydrates, such as glycogen, for energy. However, once these reserves are depleted, the animal must switch to alternative energy sources.
Fat, stored in the body as triglycerides in adipose tissue, becomes the main fuel source during prolonged periods of hibernation. Fat is an efficient energy source because it provides more energy per gram than carbohydrates or proteins. Triglycerides are broken down into fatty acids and glycerol. The fatty acids are then metabolized through processes like beta-oxidation and the citric acid cycle, generating ATP for the animal’s essential functions, such as maintaining organ function and basic metabolic activities.
This switch to fat as a primary energy source is crucial because, unlike carbohydrates and proteins, fat stores are abundant and can last for the extended duration of hibernation, which can last for months. Additionally, the process of metabolizing fat is slower than burning carbohydrates, which helps to conserve energy over the long period of dormancy.
While protein can be used for energy through gluconeogenesis (the process of making glucose from non-carbohydrate sources), it is typically not the preferred fuel because its breakdown leads to muscle loss and other detrimental effects. Therefore, fat is the most efficient and sustainable source of energy for hibernating animals.