Cellular ageing

• Lipofuscin is a complex pigment that is thought to result from end-stage lipid peroxidation probably by the oxidation of fat with free radical reactants. Its exact composition varies from cell to cell.
• Lipofuscin is a mixture of lipids and proteins containing a golden brown pigment called ceroid.
• It tends to accumulate by accretion of oxidized, cross-linked proteins and is not digestible.
• It occurs mainly in terminally differentiated cells (neurons and cardiac myocytes) or in cells that cycle infrequently(hepatocytes). 
• Also called ‘wear and tear pigment’ or ‘pigment of aging’
• Perinuclear in location
• Derived through lipid peroxidation
• Indicative of free radical injury to the cell
• Prominent in aging, severe malnutrition and cancer cachexia
• It appears to accumulate in cells with the highest metabolic activity.
• It is associated with atrophy of an organ.

Ans. is ‘a’ i.e., Free radicals injury; ‘c’ i.e., Lipofuscin accumulation

Cellular aging

o With age, there are physiologic and structural alterations in almost all organ systems.

• Aging induced alterations in cells are an important component of the aging of the organism.
• Cellular aging is the result of a progressive decline in the proliferative capacity and life span of cells and the effects of continuous exposure to exogenous influences that reslult in the progressive accumulation of cellular and molecular damge.
• The important factors that contribute to cellular aging are : ‑

1. Sencent cells have decreased capacity for repair of chromossomal damage —> accumulations of mutation —> Cellular aging.
2. Some genes influence the aging process, e.g., genes for IGF-1. Decreased signaling through the IFG-1 recepor as a result of mutations promotes aging.
3. Free radical (reactive oxygen species) mediated damage –> Free radicals cause Covalent modifications of proteins, lipids, and nucleic acids —> Cumulative damage promotes aging. Accumulations of lipofuscin is seen as the telltale sign of such damage.
4. Sencent cells, has decreased activity of the proteosomes, the proteolytic enzymes that serves to eliminate abnormal and unwanted intracellular proteins.

Ans. is ‘a’ i.e., Free redical theory

“Free radicals produced during injury or aging cause oxidative decomposition of the lipid.

Due to oxidative decomposition organic peroxides are formed after reacting with oxygen (Lipid peroxidation). This reaction is auto-catalytic i.e. new radicals are formed from the peroxide radicals themselves. These radicals cause structural and functional breakdown of endoplasmic reticulum”