After the Meal: A Museum Python's Cells at Work

Fossils Upstairs, a Live Python Downstairs

1The fossil hall of the Fernhill Museum of Natural History has a case that visitors crowd around: a fossil snake with the bones of a lizard preserved inside its body. The fossil shows what the snake ate, but it cannot show what the snake's cells did with that meal. For that, seventh grader Amaru Condori, a summer volunteer, went downstairs to the museum's live animal room, where reptile keeper Dr. Celeste Varga cares for a ball python with a mass of 1,500 g.

2Ball pythons often eat a large meal and then go a week or more without food. After a meal, the python lies almost still in its warm enclosure for days. Dr. Varga wanted to know how hard its body works during that time. She placed the python in a clear breathing box with a small air pump and an oxygen sensor for one hour each day, which measures how much oxygen the snake uses. She measured it once before a meal of a 300 g rat and again on several days after it (Table 1).

3Dr. Varga gave Amaru a model of what happens to food. In the stomach and intestines, large molecules in the rat, such as proteins and fats, are broken down into smaller molecules, such as amino acids and fatty acids. The blood carries these to cells all over the body. In cellular respiration, cells combine some of these molecules with oxygen, releasing energy and giving off carbon dioxide and water. Cells also rearrange the small molecules into new, larger molecules the snake needs, such as its own proteins and fat. Breaking food down, moving it through the gut and building new molecules all use energy.

4Over the year, the python ate meals of three sizes, each several months apart. Each time, Dr. Varga recorded the highest oxygen use and the number of days until the snake was back near its resting level (Table 2 in Section 2). She also weighed the python before the 300 g meal and again four weeks later, and she measured its length.