Could a carbon atom that was once part of Albert Einstein be in you? All living things need to take in carbon-containing molecules to fuel their activity and build their cells. This is true for busy students and for all organisms. Letâs look at how carbon atoms move through the carbon cycle in the arctic tundra. Carbon atoms from carbon dioxide are incorporated into living things by producers, such as this plant. Carbon dioxide enters a leaf, moves into a cell, and goes into a chloroplast. There, in the process of photosynthesis, carbon dioxide is used to make sugar molecules. The sugars can be used to build larger carbon-containing molecules -- carbohydrates, lipids, proteins, and nucleic acids. In this way, carbon that was in the air is now part of the plant. When a plant is eaten by an herbivore, or primary consumer, carbon in plant tissue enters the primary consumer's digestive system. There, plant molecules are broken down. These small molecules are then used by the primary consumer to make larger molecules for building its own tissues. In this way, some of the carbon that was in a plant becomes carbon in a primary consumer. Similarly, when a primary consumer is eaten by a higher-level consumer, some of the carbon in the primary consumer is incorporated into the higher-level consumer. Carbon-containing molecules in dead plant material, animal feces, and dead organisms are taken up by decomposers such as fungi and bacteria. Decomposers break down these materials and incorporate some of the carbon atoms into their own bodies. We have now seen how carbon moves from carbon dioxide to producers, to primary consumers, to higher-level consumers, and to decomposers. How does carbon get back to the atmosphere? During cellular respiration, carbon-containing molecules are broken down and ATP is made. Carbon dioxide is released as a by-product and returned to the atmosphere by producers, consumers, and decomposers. Overall, this return of carbon dioxide by cellular respiration is closely balanced by its removal from the atmosphere through photosynthesis. The global carbon cycle involves living things on land and in rivers, lakes, and oceans. And by the way, considering the huge number of carbon atoms in each person and how quickly carbon atoms move through the carbon cycle, (pause) there is almost certainly a little of Einstein in each of us.
