Most types of molecule and cellular component of animal cells are affected during ❌, and different types of animal cells have ❌.

Two of the many theories of ageing are the n❌, which states that cellular ageing is the result of a ❌, and the f❌, according to which ❌ is the cause of ❌.

Genes that confer protection against ❌ and other stresses may have a positive effect against molecular and cellular damage occurring during ❌, but will only be selected for by evolution if they also promote ❌.

Vertebrate tissues have a mixture of ❌ non-dividing cells, such as ❌ and skeletal muscle cells, and ❌ cells, such as ❌ (and germ cells).

Free ❌ are atoms or molecules that possess ❌ electrons and are therefore very ❌.

There are many naturally occurring ❌; one major source within cells is ❌, which takes place in the inner ❌ membrane.

Free radicals cause ❌ damage to all types of molecules and cell organelles.
Particularly: DNA damage - ❌ and altered bases/nucleosides, chain reactions of free radical formation in ❌, damage to amino acids causing changes to ❌ of the protein.

Cellular defences against free radicals have evolved; these are either primary or secondary defences. Primary defences include small-molecule radical ❌, proteins that bind ❌, and ❌. Secondary defences include ❌, ❌ proteins and ❌ systems.

❌ is the irreversible state reached by proliferative cells when they withdraw from the ❌, and do not undergo any further divisions. It has been studied by measuring ❌ of cells in culture.

Senescent cells exhibit changes in ❌, which may not only affect their function, but may also affect ❌. They also look different from ❌, being bigger and having larger nuclei.

Several different events can cause cells to become ❌; these include ❌ shortening, some types of DNA ❌, decondensation of ❌, overactivity of some ❌ and activation of some ❌.

❌ may be preferentially susceptible to ❌, and therefore not only trigger ❌ due to ❌ caused by repeated cell division, but also act as a type of ‘sensor’ of DNA damaging events, such as ❌.

❌ cells such as ❌ and skeletal muscle cells exhibit a number of changes during ageing. These changes include ❌, abnormalities in ❌, protein ❌, and ❌ glycation.

❌ function is impaired with age, and genes encoded by ❌ are particularly vulnerable to ❌.

Changes in protein ❌ and turnover occur with increasing age. perhaps due to problems with ❌ or the protein ❌ system. Accumulation of misfolded or ❌ proteins therefore often occurs in long-lived cells such as ❌. These can form insoluble ❌ called ❌ fibrils or plaques, causing ❌.

Interaction of ❌ with amino acid residues starts a series of reactions leading to ❌ and the accumulation of ❌ (Advanced Glycosylation End-products). Long-lived proteins (e.g. ❌) are particularly susceptible to damage by ❌.

Many segmental ❌ syndromes in humans are due to ❌ in genes encoding proteins that play a role in the detection of ❌, or DNA ❌. This suggests that DNA damage plays a role in ❌.

A ❌ in the gene encoding nuclear A-type lamins has also been found in one ❌ syndrome, ❌. ❌ are ❌, which form a structural lattice attached to the inner face of the ❌ and play a role in cell ❌ and gene ❌.

The ❌ signalling pathway in C. elegans , D. melanogaster and mice affects both ❌ and longevity.
Activation of this pathway in these three laboratory model organisms leads to ❌ of stress response genes and ❌ lifespan.
Although an ❌ pathway occurs in humans, and affects ❌ and metabolism, the effects on stress response genes and ❌ are not known.

❌ codes for several ❌ that are required in the ❌ cycle and the ❌ chain. So if mtDNA is damaged by ❌, this has huge repercussions on the cell's ability to ❌.
Combined with other age related damage to ❌ in ❌ cells, to the membrane and proteins, this can be a real problem.