The delicate balance of
chemical changes involved in recycling carbon between living and
nonliving parts of the biosphere is the pervasive theme in this module.
Photosynthesis is the process used by plants to make food. Through photosynthesis producers such as plants, algae, and some bacteria, remove carbon dioxide, an inorganic compound, and convert it into glucose for use by themselves and other living things. Glucose is the simplest organic compound and contains carbon, hydrogen, and oxygen. Glucose, often referred to as food, is used by cells and tissues in the plant as a source of chemical energy and as a source of molecules with which to build other needed compounds that make up the structure of living things.
A key element of photosynthesis is the chemical chlorophyll. Most chlorophyll is located within the leaf inside cellular structures called chloroplasts. Chlorophyll is a green pigment molecule that absorbs energy from sunlight.
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The fast track can take minutes to years to complete. Carbon moves from the soil, water or atmosphere through living things by photosynthesis, respiration, and decomposition and back to the soil, water, or atmosphere. The demand for carbon is great but only producers can convert carbon dioxide gas into carbon compounds through photosynthesis.
|This energy removes hydrogen atoms from water that enters through the plant roots and releases carbon from carbon dioxide. The carbon dioxide enters the leaves through small openings called stomata. The carbon is then trapped within the plant by energy-rich chemical bonds and, along with hydrogen, combines to form glucose. Light energy from the sun has now been transformed into chemical bond energy. Upon its release from the water molecules, oxygen exits the leaves through the stomata.|
|Most of the carbon on Earth is recycled through a slow track that can take millions of years. As marine organisms die, their shells and skeletons become buried under layers of silt on the ocean floor and their carbon becomes part of sedimentary rock. When sediments covered marine organisms before they decomposed, the resulting heat and pressure caused huge deposits of petroleum (oil) to form. Millions of years ago the remains of plants became buried in sediments under swamps where they were compacted into coal. Today, these fossil fuels are the major energy source used by humans. Burning these fuels releases carbon back into the atmosphere as carbon dioxide that is then available for the fast track.|