Mechanistic theories of ageing Flashcards
(7 cards)
What is the rate-of-living theory? Describe experimental evidence for and against.
Loeb and Northrop (1928) - The duration of life varies inversely with the rate of energy expenditure. Length of life depends on rate of living.
FOR: Drosophila - higher temperature, shorter lifespan
AGAINST: Birds similar size to mammals and expend more energy but live substantially longer.
What is the free-radical theory of ageing?
Harman (1956) - Ageing results from molecular damage caused by free radicals.
What is a free radical?
Any species capable of independent existence that contains one or more unpaired electrons. Often highly reactive with DNA, lipid and protein thereby causing damage.
How could the rate of living theory and free-radical theory link?
Mitochondrial oxidative phosphorylation generates superoxide. Higher metabolic rate, more free radicals, faster ageing.
Which theory is it?
Probably neither. Replicative senescence?
What is the hayflick limit and how are telomeres associated? Describe evidence for and against.
The Hayflick limit is the number of times a cell can divide until division stops. It is finite. In humans it is a round 50. Thought to be associated with ageing. Further developed to be associated with telomeres - as you, the more cell divisions, the shorter the telomeres.
AGAINST: Some long-lived species such as humans have shorter telomeres than mice for example. May just be sign of ageing rather than cause.
What is glycation?
When glucose, the main sugar we use as energy, binds to some of our DNA, proteins, and lipids, leaving them unable to do their jobs. The problem becomes worse as we get older, causing body tissues to malfunction, resulting in disease and death. Glycation may explain why studies in laboratory animals indicate that restricting calorie intake extends lifespan.
