Chapter 3 Textbook Notes

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Health Studies
Ingrid L.Stefanovic

HEALTH AND AGING TEXTBOOK NOTES Chapter 3: Theories of Aging Rowe and Kahn specify that successful aging consists of good physical and mental health, as well as good social functioning. Chaos theory shows how initially small changes can result in very large differences between systems or individuals. Biological processes relevant to aging, we argue, fall into two categories those that promote homeostasis and decelerate the aging process (such as DNA repair mechanisms and heat shock proteins) and those that amplify the deviations and accelerate the aging process (such as free radicals) Biological Theories of Aging Genetic Theories The maximum lifespan of a human is about 120 years, whereas that of a fruit fly is about 30 days. In general, life spans appear to be inversely related to various factors such as metabolic rate, length of time to maturation (especially sexual maturity), and response to stress. Programmed Cell Death (Apoptosis) The death gene a gene that regulates sudden cell death, a process that is also called apoptosis. Genetic materials is not static different segments turn on and off, depending on the need to synthesize proteins, perform other functions such as motility and transport, or to control the functions of other genes, including the complicated process of cell proliferation. Apoptosis is one mechanism for the destruction of cells that have proliferated for specific purposes, such as T- cells in the immune system, and need to be destroyed after having accomplished their task. The number of times a cell replicates may also be directly controlled by genes. Stochastic Processes Aging may be a function of random (or stochastic) errors. Replication error is one of the leading theories of aging. DNA is susceptible to damage by a host of environmental factors, including a variety of chemical agents. ,2,J094.,3L25,L7,.0OO8,-LOL994839K08L]057490L38,349K078:-89,3.08,3 4770854394 regulation. Cells can limit damage by turning off the damage segment and turning on identical backup segments by using DNA repair mechanisms to correct the error. Eventually, however, the cell runs out of backups, and it can no longer function adequately. DNA Repair Mechanisms Many different factors can damage DNA, including light, ultraviolet and other types of radiation, exposure to toxic chemicals, and the oxidation process itself. There are several mechanisms of DNA repair. The primary ones include base excision repair, nucleotide excision repair, mismatch repair, and repair of strand breaks. If an error is caught, replication is stopped so that repairs can be made. If the error burden is too severe, the cell undergoes apoptosis. MolecularCellular Theories of Aging Oxidation One of the most popular theories of aging is the free radical theory. Free radicals or reactive oxygen species (ROS) are molecules that are generated during the oxidation process in cells. Each ROS has an unpaired electron; thus, they are unstable and extremely chemically reactive. They can interfere with the functions of other molecules in the cell, including DNA replication, the metabolism of fatty acid chains, proteins synthesis. In part, free radicals such as superoxide can damage proteins by causing them to unfold; without proper structure, proteins cannot perform their function correctly.
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