Mitch B. answered • 09/21/20
Medical Student and Researcher
Hi Emma!
The difference between these two animals as it pertains to the question is that one is a carnivore and the other is a herbivore. The lion will be getting the majority of its calories from other animals - with the significant macromolecules being protein and fat. On the other hand, elephants will be consuming mainly grasses or fruits that are rich in carbohydrates.
Carbohydrates may be easily converted to pyruvate through a process known as glycolysis, feeding the Krebs cycle and ultimately the electron transport chain through aerobic respiration to produce ATP, the cellular currency of energy. This is what happens in elephants.
Lions however consume little to no carbs. Two processes will occur:
1) Excess amino acids obtained from their last meal (aside from leucine and lysine) may be converted to glucose (carbohydrate) through a process known as gluconeogenesis. This glucose can then be stored in the muscle or liver to be a readily available fuel source at a moments notice.
2) Lions will also consume vast amounts of fat. Fat can be used as an alternative fuel source to create energy through a state of ketosis.
All that being said, elephants get their energy from carbohydrates while lions get theirs from fat and the carbohydrates they covert from the protein they consume.
