Exam 4 Review: Chapter 24: General Metabolism Terms
nutrient - Any substance which can be metabolized by an organism to provide useful chemical energy and build tissue; components of food which fall into the general categories: carbohydrates, lipids, proteins, nucleic acids, vitamins and minerals.metabolism - The chemical processes occurring within a living cell or organism that are necessary for the maintenance of life. In metabolism some substances are broken down to yield energy for vital processes while other substances, necessary for life, are synthesized.
ATP = adenosine tri-phosphate - A nucleotide [C10H16N5O13P3] which contains the purine adenine, a pentose sugar (ribose or deoxyribose) and three high-energy phosphate groups; the potential chemical energy in the bonds connecting the phosphate groups is used to transport energy within cells for biochemical processes (including muscle contraction and enzymatic metabolism) through its hydrolysis; the mitochondrion is the primary cell organelle synthesizing this compound using energy derived from the final oxidation of nutrient molecules.
catabolism - The metabolic breakdown of complex molecules into simpler ones, resulting in a release of energy. These are the breakdown reactions of metabolism and are exergonic/exothermic; they may or may not yield an output of useful chemical energy.
anabolism - The phase of metabolism in which simple substances are synthesized into the complex materials of living tissue. These are the synthetic reactions of metabolism and are endergonic/endothermic; they require an input of useful chemical energy.
basal metabolic rate (BMR) - The rate at which energy is used by an individual at complete rest, measured by the heat given off per unit time, and expressed as the calories released per kilogram of body weight or per square meter of body surface per hour; it is regulated by thyroid hormones (T3 and T4) and epinephrine.
glucose catabolism - The series of linked enzyme catalyzed steps by which the 6-carbon monosaccharide glucose is broken down into smaller molecules with the production of some useful chemical energy for the cell; it follows two major routes: (1) anaerobic fermentation in which one glucose yields two lactate molecules and 2ATPS; this reaction, anaerobic glycolysis, occurs in the cytoplasm of cells, and (2) aerobic cellular respiration in which one glucose yields 6 carbon dioxide molecules, 12 water molecules and a maximum of 38 ATPSs; this reaction, glycolysis, begins in the cytoplasm but continues in the mitochondria (pyruvate decaroxylation, citric acid cycle, electron transport system, and oxidative phosphorylation).
glycogenesis - The anabolic synthesis of glycogen (animal starch) from glucose monomers using ATP energy which occurs primarily in hepatocytes and skeletal muscle cells; it is encouraged by insulin during the absorptive state.
glycolysis - The first and cytoplasmic portion of glucose catabolism in which glucose is converted in a series of linked enzyme catalyzed steps to pyruvic acid and useful chemical energy (net gain 2 ATPs under anaerobic conditions or net gain 2 ATPs and 2 NADH2's under aerobic conditions); techically, either route is considered anaerobic because no molecular O2 is required in any of the steps.
glycogenolysis - The enzymatic breakdown of glycogen to release glucose from the liver, primarily during the postabsorptive state, which is triggered by the action of various hormones, e.g., glucagon, human growth hormone, glucocorticoids, which may all be referred to as “insulin antagonists.”
gluconeogenesis - The formation of "new" glucose, especially by the liver, primarily during the postabsorptive state, from noncarbohydrate sources, such as pyruvate, amino acids and the glycerol portion of fats; this process is stimulated by those hormones termed "insulin antagonists," which includes glucagon, human growth hormone, and the glucocorticoids.
lipogenesis - The anabolic synthesis of neutral fats (triglycerides) or other lipids from a variety of precursor nutrients including other fats, carbohydrates, or proteins; it is one of the major functions of adipocytes and one of the many functions of hepatocytes.
Click here for a Biblical Interpretation of Lipogenesis.
lipolysis - The hydrolysis of lipids which may lead to fat catabolism
which will result in a release of useful chemical energy; this process is
stimulated by those hormones termed insulin antagonists, which includes glucagon,
human growth hormone, and the glucocorticoids; it occurs primarily during the
postabsorptive state.
Describe:
1. the relationship between catabolic pathways and anabolic pathways in metabolism.Catabolic pathways consist of reactions in which larger molecules are chemically broken apart into smaller component molecules. Catabolic pathways may require an input of energy of activation to get them started, but they are exothermic and exergonic, which means they liberate energy in one form or another as one of the products of the reaction. Some catabolic pathways yield useful chemical energy in the form of ATP or its equivalents or energetic electrons (with associated hydrogen ions) carried by specific electron transport compounds such as NAD+ and FAD+. Those catabolic pathways which liberate useful chemical energy may be coupled to anabolic pathways in order to transfer the useful chemical energy to drive the anabolic reaction. Anabolic pathways consist of reactions in which smaller component molecules are chemically joined together to make larger molecules. Anabolic pathways require considerable input of external chemical energy in order to form the bonds which link the component molecules. They are termed endothermic and endergonic for this reason.
2. the relationship between useful chemical energy and waste heat energy in metabolic reactions.
All chemical reactions involve the making and breaking of chemical bonds. The total amount of chemical energy in the reactants will not be the same as the total amount of chemical energy in the products. Even spontaneous reactions generally require some external source of energy of activation to initiate the reaction. All reactions are less than 100% efficient in energy usage and transfer and, therefore, all reactions lose some energy in the form of random molecular movement which is defined as "waste heat." In a subset of those reactions which can be termed catabolic, exothermic and exergonic, some of the energy is transferred to another form, other than waste heat. This energy may be mechanical energy of motion, creation of a voltage potential, or the storage of chemical energy in the chemical bonds of some compound. In some cases, that chemical energy is then able to be used in coupled reactions to drive other reactions. Examples of product molecules which retain this sort of useful chemical energy include ATP, NADH+ + H+ and FADH+.+ H+.
