Cell damage

Cell damage (also known as cell injury) is a variety of changes of stress that a cell suffers due to external as well as internal environmental changes. Amongst other causes, this can be due to physical, chemical, infectious, biological, nutritional or immunological factors. Cell damage can be reversible or irreversible. Depending on the extent of injury, the cellular response may be adaptive and where possible, homeostasis is restored. Cell death occurs when the severity of the injury exceeds the cell's ability to repair itself. Cell death is relative to both the length of exposure to a harmful stimulus and the severity of the damage caused. Cell death may occur by necrosis or apoptosis. Physical agents such as heat or radiation can damage a cell by literally cooking or coagulating their contents. Impaired nutrient supply, such as lack of oxygen or glucose, or impaired production of adenosine triphosphate (ATP) may deprive the cell of essential materials needed to survive. Metabolic: Hypoxia and Ischemia Chemical Agents Microbial Agents: Virus & Bacteria Immunologic Agents: Allergy and autoimmune diseases such as Parkinson's and Alzheimer's disease. Genetic factors: Such as Down's syndrome and sickle cell anemia The most notable components of the cell that are targets of cell damage are the DNA and the cell membrane. DNA damage: In human cells, both normal metabolic activities and environmental factors such as ultraviolet light and other radiations can cause DNA damage, resulting in as many as one million individual molecular lesions per cell per day. Membrane damage: Damage to the cell membrane disturbs the state of cell electrolytes, e.g. calcium, which when constantly increased, induces apoptosis. Mitochondrial damage: May occur due to ATP decrease or change in mitochondrial permeability. Ribosome damage: Damage to ribosomal and cellular proteins such as protein misfolding, leading to apoptotic enzyme activation. Some cell damage can be reversed once the stress is removed or if compensatory cellular changes occur.