Chapter 6 Metabolism
The chemistry of life is organized into metabolic pathways
Metabolism = Totality of an organism’s chemical processes.
Property emerging from specific molecular interactions within the cell.
Concerned with managing cellular resources: material and energy.
Metabolism begins by the assimilation of nutrients into the body of an organism.
This results in a series of stepwise chemical transformations of the nutrient structure.
There are two main pathways involved:
Catabolic pathways = Metabolic pathways which release energy by breaking down complex molecules to simpler compounds. (e.g. Cellular respiration which degrades glucose to carbon dioxide and water; provides energy for cellular work.). This applies to a pathway which proceeds to break down large complex structures into simple molecules such as carbon dioxide, amino acids, ammonia and urea. Under this condition, the function is extraction (production) of energy from the bonds of the nutrients.
Anabolic pathways = Metabolic pathways which consume energy to build complicated molecules from simpler ones (e.g. Photosynthesis which synthesizes glucose from CO2 and H2O). So, this is a biosynthetic pathway leading to the production of large complex molecules such as polymeric molecules called polysaccharides, proteins or nucleic acids. This pathway consumes energy. Anabolic steroids promote biosynthetic pathways, particularly the biosynthesis of proteins in muscles.
Metabolic reactions may be coupled, so that energy released from a catabolic reaction can be used to drive an anabolic one.
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and there are several ways in which the two pathways are linked.
Organisms transform energy
Energy = Capacity to do work
Kinetic energy = Energy in the process of doing work (energy of motion). For example: Heat (thermal energy) is kinetic energy expressed in random movement of molecules. Light energy from the sun is kinetic energy which powers photosynthesis.
Potential energy =