AP Notes, Outlines, Study Guides, Vocabulary, Practice Exams and more! Enter the terms you wish to search for. To perform their many tasks, living cells require energy from outside sources. Energy enters most ecosystems as sunlight why are enzymes needed for cellular respiration leaves as heat. Photosynthesis generates oxygen and organic molecules that the mitochondria of eukaryotes use as fuel for cellular respiration.
Cells harvest the chemical energy stored in organic molecules and use it to regenerate ATP, the molecule that drives most cellular work. Respiration has three key pathways: glycolysis, the citric acid cycle, and ap biology multiple choice grading scale phosphorylation. The arrangement of atoms of organic molecules represents potential energy. Enzymes catalyze the systematic degradation of organic molecules that are rich in energy to simpler waste products with less energy. Catabolic metabolic pathways release the energy stored in complex organic molecules.
One type of catabolic process, fermentation, leads to the partial degradation of sugars in the absence of oxygen. A more efficient and widespread catabolic process, cellular respiration, consumes oxygen as a reactant to complete the breakdown of a variety of organic molecules. In eukaryotic cells, mitochondria are the site of most of the processes of cellular respiration. Cellular respiration is similar in broad principle to the combustion of gasoline in an automobile engine after oxygen is mixed with hydrocarbon fuel.
Food is the fuel for respiration. The exhaust is carbon dioxide and water. Carbohydrates, fats, and proteins can all be used as the fuel, but it is most useful to consider glucose. The catabolism of glucose is exergonic with a ? 686 kcal per mole of glucose.
Some of this energy is used to produce ATP, which can perform cellular work. Redox reactions release energy when electrons move closer to electronegative atoms. Catabolic pathways transfer the electrons stored in food molecules, releasing energy that is used to synthesize ATP. Reactions that result in the transfer of one or more electrons from one reactant ap biology lab mitosis and cancer another are oxidation-reduction reactions, or redox reactions. The loss of electrons is called oxidation. The addition of electrons is called reduction.
The formation of table salt from sodium and chloride is a redox reaction. X, the electron donor, is the reducing agent and reduces Y. Y, the dosage of digestive enzymes for dogs recipient, is the oxidizing agent and oxidizes X. Redox reactions require both a donor and acceptor. Redox reactions also occur when the transfer of electrons is not complete but involves a change in the degree of electron sharing in covalent bonds. When methane reacts with oxygen to form carbon dioxide, electrons end up farther away from the carbon atom and closer to their new covalent partners, the oxygen atoms, which are very electronegative. Thus, methane has been oxidized.