Human chromosomes

Getting on a bit

Ageing cells have a number of tell-tale signs

Over time, the waste disposal system in the cell can get clogged up. Old, tangled proteins and other bits of cellular junk defy the lysosomal enzymes. Remnants of fatty acids are a particular problem and they make up a big portion of the yellowish pigment granules known as lipofuscin, the appearance of which is a sure sign of an ageing cell.

Other signs of cell ageing, such as shortening of the telomeres on the ends of the chromosomes, are related to how many times the cell has divided. Most, though, are the result of normal wear and tear. Mitochondria age faster than other organelles. Their job of energy release through aerobic respiration exposes them to reactive chemicals – free radicals – that can damage DNA.

Mitochondria have some essential genes in their own DNA, and the proportion of them that have serious defects increases as the person and their cells grow older; this can cause a decline in mitochondrial function.

Recent research has suggested a method of ‘reversing’ this mitochondrial ageing process by injecting mice with nicotinamide mononucleotide (NMN) to increase nicotinamide adenine dinucleotide (NAD), which is important in aerobic respiration.

Lead image:

Human chromosomes.

Wellcome Images CC BY NC


About this resource

This resource was first published in ‘The Cell’ in February 2011 and reviewed and updated in September 2015.

Cell biology, Immunology, Health, infection and disease
The Cell
Education levels:
16–19, Continuing professional development