What Is The Carbon Cycle - Part 2

Watch part 2 of the videos on the Carbon Cycle, as a part of environmental chemistry. Photosynthesis and respiration help carbon to be cycled in nature by using energy from the sun. As living things grow, they have to build up large polymer molecules from small molecules. Protein comes from joining amino acids together, cellulose and starch from joining sugars, and DNA from the bases, sugar and phosphate. Plants can make these simple molecules from the carbon they capture from photosynthesis with added elements from the minerals that they get from the soil. Animals have to get their molecules ‘ready made’ when they eat plants or other animals - but first they have to break the food polymers back into the small molecules through digestion. This all needs lots of energy. Living things get their energy from respiration. Some of the monomers (often carbohydrates in humans) have to be re-joined with oxygen. The carbon dioxide gets back into the food web through photosynthesis. Mankind has had an influence on the carbon cycle. The carbon dioxide released during respiration is cycled naturally. Same is the case if we burn wood and agricultural waste – even biogas given off from food we throw onto rubbish tips and from sewage works. All this carbon has been recently captured from the atmosphere and we are simply returning it to be used again in the natural cycle. However when we burn fossil fuels the carbon in them has been underground for 100’s of millions of years, and this adds new carbon dioxide to the atmosphere.