0520 Aging and Cell death Flashcards
What is the difference between senescence and aging
Senescence = process or condition of growing old. Aging = the gradual changes in the structure of any organism over time. The difference is senescence refers to specific cell effects while aging refers to whole organisms
What is life span and life expectancy? What are the differences
Life span = age at which 50% of the population survives. Life expectancy is the expected number of years of life remaining at any given age. Life span refers to populations while life expectancy refers to individuals
In terms of life span and maximum potential life span, which figure has increased over time
While life span has increased, maximum potential life span has remained relatively stable
What is the ‘biological’ clock phenomenon observed in invitro culture cells
Cultured cells will become vegetative or die (no divide anymore) after a certain period of time
What are telomeres
Telomeres are regions of repetitive nucleotide sequences at the end of each chromatid
Explain the role of telomeres
Telomeres protect the ends of chromosomes. Enzymes duplicating DNA cannot continue all the way to the end. Thus, telomeres act as disposable buffers at the ends of chromosomes
What is the role of telomerase
Tolermase is an enzyme that produces telomeres at the ends of chromosomes, Generally, telomerase activity in somatic cells in minimall
What is the role of telomerase in malignancy
In continually replicating cells (e.g. cancer cells), Telomerase activity is increased which leads to a en excess of telomeres
List and briefly describe the components of ageing
Protein modification (qualitative changes in function of proteins), free radical damage and mitochondrial DNA (mutations due to free radicals), DNA damage accumulation (accumulation over time of problematic mutations) and mTOR (a protein kinase that regulates cell growth, proliferation, motility and survival)
List in order of longest viable cell replication periods, cells taken from samples of; a newborn, a 100 yr/o and a patient with werner’s syndrome (adult progeria)
Newborn, 100 yr/o and werners syndrome
Give two examples of cells where telomere length remains the same or increases over time
Germ cells and malignant cancer cells
Why are mitochondrial DNA much more susceptible to free radical damage.
Mitochondrial DNA have a mucher higher rate of activity = increased production of free radicals. Furthermore, mitochondrial DNA repair mechanisms are less efficient than those found in the nucleus
What is mTOR and is it’s relevance to aging
mTOR = Mammalian target of rapamycin is a protein in humans encoded in the mTOR gene. It is a protein kinase (enzyme) that regulates cell growth, proliferation, motility and survival. Studies have shown that inhibiting the action of mTOR has lead to increased extended the life span of mice
List at least 4 histological morphology changes of senescence
Nuclei (irregular and lobulated), Mitochondria (vacuolated and pleimorphic), ER (decreased activity and complexity), Golgi (distored) and accumulation of pigment
Describe the role of melanogenesis in hair pigmentation
Melanocytes at the base of hair follicules produce the pigment melanin (melanogenesis). As we age, melanocytes do not migrate as easily, tyroinsase activity decreases and we lose our hair colour
