Chapter 3 notes

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Published on 17 Jun 2011
School
UTSC
Department
Health Studies
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HLTC22H3
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Chapter 3- Theories of Aging
-The aging process can occur at the biological, psychological, and social level
-Bengston, Rice and Johnson (1999)= 3 aspects of age on which theories focus-
characteristics of the aging population, the developmental or aging process, and the
way in which age is incorporated into the social structure
-Successful aging consists of good physical and mental health as well as good social
functioning
-Kuypers and Bengstons (1973) social breakdown theory argues that physical,
psychological, and social health are tightly linked in later life, and problems in one
area may cause or accelerate problems in another area
Biological Theories of Aging
-Genetic Theories
oMaximum life span of human is 120 years, fruit life 30 days
oProgrammed Cell Death (Apoptosis)
Death gene; a gene that regulates sudden cell death= called apoptosis
Genetic material 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
Damage to these regulator proteins may be one mechanism for cancer
that is uncontrolled 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 needed to be destroyed after having accomplished their
task
Fetal cells replicate more times than an adult cell
There is a positive correlation between life span of a species and the
number of times a cell will replicate; for humans ex. The number of
times a somatic cell can replicate is partially regulated by the
telomere length. Telomere consists of the specialized ends of DNA
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strands that help hold them together during mitosis. DNA strands do
not completely unwind during this phase, but are held together by
these caps at their ends, which do not replicate and thus are lost.
Telomeres can be replaced by enzyme telomerase
In cancer cells they have much longer telomeres and more active
telomerase than normal cells
Recent research identified immortality genes which regulate cell
senescence. Mutations in this gene invokes immortality; cells appear
to replicate infinitely. The nonmutated versions of these genes appear
to regulate senescence.
Senescence is the major protection against cancer and is described as
a form of antagonistic pleiotrophy (process to help reproduction in
early life but may be harmful later life)
oStochastic Processes
Random (stochastic) errors
DNA is susceptible to damage by a host of environmental factors,
chemical agents, & radiation, and internal processes (oxidation).
Damage to DNA can impair a cells ability to synthesize proteins &
respond to regulation. Cells usually limit this damage by turning off
the damaged segment & turning on identical backup segments or by
using DNA repair mechanisms to correct the error, the cell eventually
runs out of backup.
Oxidation occurs in the mitochondria; and thus it is susceptible to
damage. If the cells energy source is damaged then the functioning
will be impaired & becomes candidate for apoptosis. Damaged
mitochondrial DNA= cell loss in late life
oDNA Repair Mechanisms
DNA can be repaired= a deviation countering mechanism for aging
Ultraviolet & other types of radiation, exposure to toxic chemicals, and
oxidation can damage DNA
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Damage activates transcription & replication. In replication, several
different checkpoints are placed through which cell checks integrity of
the DNA strands. If error caught= replication stopped
Repair= Base excision repair, nucleotide excision repair, mismatch
repair, & repair of strand breaks
If damage can be tolerated= replication by pass, if to severe=
apoptosis
- Molecular/Cellular Theories of Aging
oOxidation
Free radicals/reactive oxygen species (ROS) molecules generated in
oxidation
ROS has unpaired electrons= unstable & extremely chemically
reaction
Can interfere with other functions ex. Molecules in cell, DNA
replication, metabolism of fatty acid chain, DNA transcription &
protein synthesis
Free radical (superoxide) can damage proteins by causing them to
unfold without proper structure, thus they cant perform properly
Concentration of free radical increases with age b/c : 1) more f.r.
generated in aging cells 2) decrease in ability of cell 2 generate
antioxidants 3) cellular repair mechanism becomes less efficient
oLipofuscin
Aging cells accumulate waste matter= lipofuscin. Dark mixture of
lipoproteins & various waste products
Usually disposed through liposomal enzymes but in older cells it is
impaired
Found in all cells; heart muscle cells to neurons, and increases with
age
Recent findings: lipofuscin associated with Alzheimers
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Document Summary

The aging process can occur at the biological, psychological, and social level. Bengston, rice and johnson (1999)= 3 aspects of age on which theories focus- characteristics of the aging population, the developmental or aging process, and the way in which age is incorporated into the social structure. Successful aging consists of good physical and mental health as well as good social functioning. Kuypers and bengston"s (1973) social breakdown theory argues that physical, psychological, and social health are tightly linked in later life, and problems in one area may cause or accelerate problems in another area. Genetic theories: maximum life span of human is 120 years, fruit life 30 days, programmed cell death (apoptosis)  death gene; a gene that regulates sudden cell death= called apoptosis.  damage to these regulator proteins may be one mechanism for cancer that is uncontrolled cell proliferation.