Write down the mechanism of irreversible cell injury.

Mechanisms of cell injury are as follows:

• Depletion of ATP: Reduction in ATP levels is fundamental cause of necrotic cell death. ATP depletion and decreased ATP synthesis are frequently associated with both hypoxic and chemical injury. The  major causes of ATP depletion are reduced supply of oxygen and nutrients, mitochondrial damage, and the actions of some toxins.
• Mitochondrial Damage: Mitochondria are critical players in cell injury and cell death by all pathways. Mitochondria can be damaged by increases of cytosolic Ca2+, reactive oxygen species, oxygen deprivation and mutations in mitochondrial genes in some inherited diseases.
• Influx of Calcium and Loss of Calcium Homeostasis: Calcium ions are important mediators of cell injury.
• Accumulation of Oxygen-Derived Free Radicals: Cell injury induced by free radicals, particularly reactive oxygen species, is an important mechanism of cell damage in many pathologic conditions, such as chemical and radiation injury, ischemia-reperfusion injury, cellular aging, and microbial killing by phagocytes.
• Defects in Membrane Permeability: Early loss of selective membrane permeability, leading ultimately to overt membrane damage, is a consistent feature of most forms of cell injury. Membrane damage may affect the functions and integrity of all cellular membranes.
• Damage to DNA and Proteins.