Theories of Aging

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Theories of Aging
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Free-radical theory of aging

• cells accumulate free radical damage with the
  passage of time
• a "free radical" is any molecule that has a
  single unpaired electron in an outer shell are
  fairly reactive.
• free radical damage is closely associated with
  oxidation damage
• oxidation is the loss of electrons from the atoms
  and molecules
• antioxidants like vitamin C prevent oxidation as
  electron donators.

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Mitochondrial theory of aging

• Mitochondria are the energy generators of the
  cell.
• produce 90 or more of all the ATP bioenergy made
  in the body
• have their own DNA
• do not have protections against free radical
  damage.

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Evolutionary theories of aging

• how evolution designs organisms to achieve
  reproductive success
• 1) programmed death (cell division limit)
  August Weismann,
• 2) mutation accumulation theory -Peter Medawar
• 3) antagonistic pleiotropy theory - George
  Williams.
• 4) disposable soma theory - Tom Kirkwood/Robin
  Holliday.

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Mutation accumulation theory

• Over successive generations, mutations accumulate
  and are passed on.
• This leads to an increase in mortality rates late
  in life after the reproductive years.
• This does not affect mutations causing death
  prior to reproductive years.

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Antagonistic pleiotropy theory

• Late-acting deleterious genes may even be favored
  by selection and be actively accumulated in
  populations if they have any beneficial effects
  early in life. 

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Disposable soma theory

• a special class of gene mutations
• save energy for reproduction (positive effect) by
  partially disabling molecular proofreading and
  other accuracy promoting devices in somatic cells
  (negative effect).
• to accelerate development and reproduction

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Social Conceptions of Age

• Social age
• Chronological age
• Boilogical age
• Mental age