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In respiratory physiology, the oxygen cascade describes the flow of oxygen from air to mitochondria, where it is consumed in aerobic respiration to release energy. [1] Oxygen flows from areas with high partial pressure of oxygen (PO 2 , also known as oxygen tension ) to areas of lower PO 2 .
The upper limit for the oxygen pathway is called the V o2max. V o2max is the maximal oxygen capacity that systems can take in, transport, and use oxygen. [3] [6] V o2max can vary among individuals due to allometric variation (the differences in body mass), adaptive variation (differences in lifestyles), and the induced variation (amount of ...
The oxygen reduction reaction is an essential reaction for aerobic organisms. Such organisms are powered by the heat of combustion of fuel (food) by O 2.Rather than combustion, organisms rely on elaborate sequences of electron-transfer reactions, often coupled to proton transfer.
The intrinsic pathway is also known as the caspase cascade and is induced through mitochondrial damage which triggers the release of cytochrome c. DNA damage, oxidative stress, and loss of mitochondrial membrane potential lead to the release of the pro-apoptotic proteins mentioned above stimulating apoptosis. [68]
Respiratory burst requires a 10 to 20 fold increase in oxygen consumption through NADPH oxidase (NOX2 in humans) activity. NADPH is the key substrate of NOX2, and bears reducing power. Glycogen breakdown is vital to produce NADPH. This occurs via the pentose phosphate pathway. The NOX2 enzyme is bound in the phagolysosome membrane.
The HIF signaling cascade mediates the effects of hypoxia, the state of low oxygen concentration, on the cell. Hypoxia often keeps cells from differentiating . However, hypoxia promotes the formation of blood vessels , and is important for the formation of a vascular system in embryos and tumors.
The glyoxylate shunt pathway is an alternative to the tricarboxylic acid (TCA) cycle, for it redirects the pathway of TCA to prevent full oxidation of carbon compounds, and to preserve high energy carbon sources as future energy sources. This pathway occurs only in plants and bacteria and transpires in the absence of glucose molecules. [13]
[31] [32] The Nrf2/ARE signalling pathway has a fundamental role at fighting against oxidative stress, to which neurons are especially vulnerable due to its high oxygen consumption and high lipid content. This neuroprotective pathway involves control of neuronal activity by perisynaptic astrocytes and neuronal glutamate release, with the ...