chapter 3 notes

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20 Jun 2011
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
-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 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,
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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
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
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