Fuel for the Flight: Cellular Respiration at a Wildlife Refuge

Fuel for a Long Flight

1Each May, thousands of small shorebirds called sandpipers stop at the mudflats of the Bayshore Wildlife Refuge on their way north to their nesting grounds. Many stay for about one to two weeks, feeding on worms, small clams and tiny crabs from the mud. Volunteers at the refuge's banding station, including seventh grader Tavita Faleolo, help catch birds in fine nets. Each bird gets a small numbered band on one leg, is weighed and is released. When a banded bird is caught again, its new mass can be compared with its old one.

2Food has to be processed before a bird's body can use it. In the digestive system, large food molecules are broken down into smaller ones, such as sugars and amino acids, which the blood carries to every cell. Cells can rearrange these small molecules into new large molecules, such as fat stored under the skin or proteins in muscle. Cells also release energy from food through cellular respiration, which can be summarized as: sugar or fat + oxygen → carbon dioxide + water, releasing energy.

3Table 1 shows four sandpipers that were weighed when they arrived and caught again 10 days later. Bird D19 was caught a third time at another refuge several hundred kilometers to the north, two days after it left Bayshore. That time it had a mass of 26 g.

4The refuge's nature center raises mealworms, the larvae of a beetle, to feed injured birds. A visiting class used them to study cellular respiration. They placed 2 g of mealworms in each of two sealed 1 L chambers, one kept at 25 °C and one kept at 10 °C in a cooler. A third chamber at 25 °C was left empty. A sensor measured the carbon dioxide in each chamber, in parts per million (ppm), at the start and after 30 minutes (Table 2 in Section 2). A mealworm's body temperature stays close to the temperature of the air around it.