Instructional Model

Teacher Guide

Teacher Background

Printable Materials






About the Author



Compounds that neutralize oxygen radicals. Some are enzymes like SOD while others are nutrients such as vitamin C, E, and beta-carotene.
Average life span
The average number of years that members of a population live.
Caloric restriction
An experimental approach in which life spans of laboratory animals have been extended by reducing calories while the necessary level of nutrients is maintained.
Cell senescence
The stage at which a cell has stopped dividing permanently.
Differentiation Pluripotent stem cells undergo further specialization into stem cells that are committed to give rise to cells that have a particular function.
Free radicals
Molecules with unpaired electrons that react readily with other molecules. Oxygen-free radicals, produced during metabolism, damage cells and may be responsible for aging in tissues and organs.
Heat Shock Proteins Produced when cells are exposed to stresses, heavy metals, and chemicals. Levels at which they are produced depend on age.
Substances secreted by lymphocytes: their levels vary with age.
Maximum life span
The greatest age reached by any member of a given species.
The process initiated by sunlight through which the skin becomes drier and loses elasticity.
SOD Superoxide dismutase; converts oxygen radicals into hydrogen peroxide, which then degrades to oxygen and water.
Repeated DNA sequences found at the ends of chromosomes; telomeres shorten each time a cell divides.
Enzyme in specialized reproductive cells and most cancer cells, which adds back telomeric DNA to the ends of chromosomes. Causes human cells to continue to divide long past the time when they normally stop dividing.