Some of the chemical energy gets used to do work, some of it gets lost as heat. Breakdown pathways are called catabolic pathways. One such catabolic pathway is fermentation no oxygen. A more prevalent pathway that is more efficient is called cellular respiration. Oxygen is combined with organic molecules to release energy. All types of macromolecules can be broken down and used as fuel. Typically we study the degradation of glucose:. We tend to ingest proteins, carbohydrates and fats within our diets.
If we use tose types of molecules for their energy content as opposed to using them for their A spare parts to build some new molecules the molecules are broken into intermediary molecules that enter into the respiratory pathway of glucose somewere along the line. Cellular respiration does not directly move flagella, pump solutes or do any of the cellular work. Cellular respiration generates ATP, which is in turn expended by the cell to do work. Remember that ATP is like a loaded spring.
That process is called phosphorylation. You should read modules 6. They cover pretty much what I have said in class about cellular respiration. Where does the rest of the energy go? This may be of interest to you. Note they use the term A K-cal or A kilocalorie. This is the equivalent of what we refer to in everyday language as a Calorie.
Enzymes are catalysts. Catalysts are chemical agents that change the rate of a reaction without being consumed by the reaction. These are what regulate the various reactions of metabolism. Even though many reactions are exergonic they still require some energy to get them going. This extra boost is called the activation energy. Enzymes function to lower the activation energy necessary to start reactions. They do not affect the net energy change of the equation.
The reactant an enzyme works on is called its substrate. Enzymes are very substrate specific. They are usually proteins. Recall that proteins have specific shapes. There is a region of the enzyme called the active site where the substrate molecule s fit.
The catalyst enzyme can do a number of things to facilitate the reaction. It can twist the molecules promoting bond breaking, it can serve as a template to bring to substrate molecules into proper position, it can provide a "microenvironment" conducive to promoting the reaction eg. Many things effect the action of enzymes. Most enzymes function in a specific optimal range of temperature and pH. As mentioned previously, to grow, function, and reproduce, cells must synthesize new cellular components such as cell walls, cell membranes, nucleic acids, ribosomes, proteins, flagella, etc.
Catabolism refers to the exergonic process by which energy released by the breakdown of organic compounds such as glucose can be used to synthesize ATP, the form of energy required to do cellular work.
Anabolism is the endergonic process that uses the energy stored in ATP to synthesize the building blocks of the macromolecules that make up the cell. As can be seen, these two metabolic processes are closely linked. Another factor that links catabolic and anabolic pathways is the generation of precursor metabolites.
Precursor metabolites are intermediate molecules in catabolic and anabolic pathways that can be either oxidized to generate ATP or can be used to synthesize macromolecular subunits such as amino acids, lipids, and nucleotides. In this section we will concentrate primarily on harvesting energy and converting it to energy stored in ATP through the process of cellular respiration, but we will also look at some of the key precursor metabolites that are produced during this process.
Cellular respiration is the process cells use to convert the energy in the chemical bonds of nutrients to ATP energy.
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