Report in cell biology


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Aging is one of the most hated occurence in our life....

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Report in cell biology

  1. 1. REPORT IN CELL BIOLOGY THE FREE RADICAL THEORY OF AGING Ronnie Z. Valenciano Jr. BSE 3B College of Development Education, Central Bicol State University of AgricultureIntroduction We probably think of aging as one of the most hated occurrence in life, especially to the teenagers. Teenagersare afraid to look too old at their young age. Sometimes they’re blaming the stress cause by hectic class schedule andthe overdued projects required by their professors. Meanwhile to lessen up the sagging and drying of their skin, theyprefer to walk on the shaded areas and use lotion with high formulation of SPF (Sun Protection Factor). Are teenagersright in doing that defense mechanism to prevent aging? How does aging occur to the human body? Another intriguing issue about longevity of life span is on the difference on life span of human and animals.Human life expectancy is higher compared to the animals. What would be the reason of this phenomenon? Do theirlifestyles affect the span of their life? The answer may dwell on the report about the Free Radical Theory of Aging. Aging is cause by an atom which has unpaired electrons, making an atom highly reactive. It results to the termFree Radical. Free radical usually attacked mitochondria- the powerhouse of the cell by the process of electron transportchain where oxygen is utilizes to generate energy. To destroy these highly reactive atoms antioxidants are applied toneutralize the unstable atoms.Discussion of Topics What is Free Radical? Free radicals are atom or group of atoms with at least one unpaired electronmaking it in unstable state, hence making it very reactive. These are organic moleculesresponsible for ageing, tissue damage and possibly diseases. In the body it is usually an oxygenmolecule that has lost electron and will stabilize itself by stealing an electron from a nearbymolecule. These are the high energy particles that ricochet wildly and damage cells. Free Radical Formation Atoms are most stable in the ground state. An atom is considered to be"ground" when every electron in the outermost shell has a complimentary electron that spinsin the opposite direction.If an atom is excited, for example by being exposed to heat, one or more of its electrons maytemporarily transferred to an orbital of higher energy, but it will soon return to its groundstate. A free radical is easily formed when a covalent bond between entities isbroken and one electron remains with each newly formed atom. Free radicals are highlyreactive due to the presence of unpaired electron(s). The most common radical in the biological system is the radical oxygen, whichis being referred as reactive oxygen species (ROS). Its production occurs mostly within the mitochondria of the cell.Mitochondria are small membrane-enclosed regions of a cell that produce the chemicals a cell uses for energy.Mitochondria accomplish this task through a mechanism called the "electron transport chain." In this mechanism,electrons are passed between different molecules, with each pass producing useful chemical energy. This is found in theinner mitochondrial membrane, which utilizes oxygen to generate energy in the form of ATP. Oxygen occupies the finalposition in the electron transport chain. Occasionally, the passed electron incorrectly interacts with oxygen, producingoxygen in radical form, thus chain reaction continues and can be “thousands of events long”. For example, water can be converted into free radicals when exposed to radiation from the sun. Radiation H2O HO· + H· (“·” indicates free radical) hydroxyl radicals Free Radical Damage The primary site of radical oxygen damage is mitochondrial DNA (mtDNA). Every cell contains anenormous set of molecules called DNA which provide chemical instructions for a cell to function. This DNA is found inthe nucleus of the cell, which serves as the "command center" of the cell, as well as in the mitochondria.
  2. 2. The cell fixes much of the damage done to nuclear DNA. However, mitochondrial DNA (mtDNA) cannot be readily fixed.Therefore, extensive mtDNA damage accumulates over time and shuts down mitochondria, causing cells to die and theorganism to age. Protection against Free Radicals On 1969, Joe McCord and Irwin Fridovich of Duke University discovered anenzyme, superoxide dismutase (SOD). Where function was the destruction of superoxideradical (O2·–) ( SOD) O2·– + O2·– + 2H H2O2 + O2 If H2O2 becomes free radicals, it is normally destroyed by the enzymecatalase or glutathione peroxidase. Another way to protect the cell from radicals is by antioxidants. Antioxidantsneutralize free radicals, it donate an electron; which make the chain reaction ends.Recommendation Unlocking the mystery of aging clarifies the issue about the problem on longevity of the human lifeexpectancy, thus it is recommended to: 1. Make further study on discovering other enzymes against free radicals. 2. Enhance natural antioxidants in our body and lessen up intake of dietary supplements. 3. Apply this knowledge on further research in development of practical method to prevent and repair free radical damageReferencesAlumaga, Marie Jessica B. et al. Conceptual and Functional Chemistry Modular Approach. Vibal Publishing House: Quezon City,2010.Molecular and Cell Biology, pp. 35-36.
  3. 3. Free radicals are atoms with unpaired electrons. According to the free radical theory,radicals damage cells in an organism, causing aging. Mitochondria, regions of the cell thatmanufacture chemical energy, produce free radicals and are the primary sites for free radicaldamage. By eliminating free radicals from cells through genetic means and dietary restriction,laboratories have extended the maximum age of laboratory animals. The administration ofantioxidants, which eliminate radicals, to laboratory animals fails to increase maximum lifespan.The nucleus of an atom is surrounded by a cloud of electrons. These electrons surround thenucleus in pairs, but, occasionally, an atom loses an electron, leaving the atom with an unpairedelectron. The atom is then called a "free radical," or sometimes just a "radical," and is veryreactive. When cells in the body encounter a radical, the reactive radical may cause destruction inthe cell. According to the free radical theory of aging, cells continuously produce free radicals, andconstant radical damage eventually kills the cell. When radicals kill or damage enough cells in anorganism, the organism ages.1The production of radical oxygen, the most common radical in biological systems, occurs mostlywithin the mitochondria of a cell. Mitochondria are small membrane-enclosed regions of a cellthat produce the chemicals a cell uses for energy. Mitochondria accomplish this task through amechanism called the "electron transport chain." In this mechanism, electrons are passedbetween different molecules, with each pass producing useful chemical energy. Oxygen occupiesthe final position in the electron transport chain. Occasionally, the passed electron incorrectlyinteracts with oxygen, producing oxygen in radical form.2
  4. 4. The primary site of radical oxygen damage is mitochondrial DNA (mtDNA). Every cell contains anenormous set of molecules called DNA which provide chemical instructions for a cell to function.This DNA is found in the nucleus of the cell, which serves as the "command center" of the cell, aswell as in the mitochondria. The cell fixes much of the damage done to nuclear DNA. However,mitochondrial DNA (mtDNA) cannot be readily fixed. Therefore, extensive mtDNA damageaccumulates over time and shuts down mitochondria, causing cells to die and the organism toage.4Protection of mtDNA from radicals slows aging in laboratory animals. Some laboratories haveproduced fruit flies that live one-third longer than normal fruit flies. These labs genetically alteredthe fruit flies to produce more natural antioxidants. Antioxidants are molecules that eliminateradicals, so elevated levels of antioxidants prevent much of the mtDNA damage done by radicals.3Other labs severely restricted the food intake of laboratory rats, causing a 50% increase inmaximum lifespan compared to rats allowed to eat freely.2 The mitochondria of starved rats arenot provided with enough material to function at full capacity. Therefore, the electron transportchains in mitochondria of the starved rats pass fewer electrons. With fewer electrons passed,fewer oxygen radicals are produced, so aging slows.One main problem with the free radical theory is the failure of antioxidants administered asdietary supplements, like vitamins E and C, to significantly increase maximum lifespan.Proponents of the radical theory believe that dietary antioxidants, unlike natural antioxidantsproduced by cells, do not reach mitochondrial DNA, leaving this site susceptible to radical attack.Interestingly, even though supplemental antioxidants fail to increase maximum lifespan, they doincrease the chances of living to the maximum lifespan. This may be due to antioxidant protectionof other parts of the cell, like cellular proteins and membranes, from radical damage.2The goal of all research on the free radical theory is to slow aging and increase maximum lifespan.The achievements so far are astounding; increasing the lifespan of fruit flies and rats is animpressive feat. Despite such success, no practical applications of the theory have been perfected.Genetic alteration is both controversial and difficult for humans. Starvation, while lengtheninglifespan, is an unappealing alternative. Dietary antioxidants fail to increase maximum lifespan.However, the production of radicals and their role in aging is well understood. Further researchmay apply this knowledge in the development of a practical method to prevent or repair mtDNAradical damage. //