The cell and aging

The Cell and Aging

Getting old from the inside out

What is aging?

• The progressive changes that occur in an organism, leading to increased risk of disability, disease, and death.

Aging, or getting old, starts at the cellular level.

Theories of aging

• Genome Maintenance Hypothesis

• Replicative Senescence Hypothesis

• Oxidative Damage/Free Radical Hypothesis

Genome Maintenance Hypothesis

• Aging comes from damage to our DNA

• Caused by toxins, radiation, mistakes in replication and free radicals

• Mutations in DNA that are not corrected cause cells to malfunction and die, leading to aging.

To explore this hypothesis, we must enter the nucleus of a cell.

DNA replication copies the DNA before cell division.

Multiple Choice

What is the term for cell division?

• genomic maintenance

• DNA replication

• mitosis

• oxidation

Multiple Choice

What is the term for copying the DNA before cell division?

• DNA replication

• mitosis

• mutation

• genomic maintenance

Mutations are changes in the DNA sequence

• can be random mistakes during replication

• can be caused by chemicals

• can be caused by radiation

Normally, our body fixes these mistakes...

but not always.

Multiple Choice

What is a mutation?

• the process of copying DNA

• a change in the DNA sequence

• a chromosome

• the process in which our risk is increased for disease, disability, and death

Multiple Choice

All of the following are mutagens (cause mutations) EXCEPT

• x-radiation.

• UV light.

• certain chemicals.

• histones.

Replicative Senescence Hypothesis

• linked to cell division process

• each division shortens the telomeres

• the shorter the telomeres are, the more likely they are to break, causing problems with the function of the DNA

Multiple Choice

What is a telomere?

• a change in the DNA sequence

• An enzyme that is used to initiate the process of DNA replication

• a long stretch of repetitive DNA sequences found on the end of a chromosome

• a gene for making a protein

The Hayflick limit is the number of times a cell can divide before the telomeres get too short.

Poll

What do you think the Hayflick limit is?

• 1000 to 2000 rounds of mitosis

• 40 to 60 rounds of mitosis

• 5 to 10 rounds of mitosis

• 200 to 400 rounds of mitosis

Oxidative Damage/Free Radical Hypothesis

• caused by free radicals

• are caused by atoms with unpaired elctrons that rob other molecules of their electrons

90% of cell's free radicals are produced in the mitochondria.

Mitochondria damaged by free radicals cannot repair DNA errors, causing more problems.

Antioxidants can repair free radicals

Poll

Which hypothesis is most reasonable to you?

• genomic maintenance

• oxidative damage/free radical

• replicative senescence

• all of them