The final step of cellular phosphorylation in which oxygen is used to a create an electron transport chain that produces a large amount of ATP from nicotinamide adenine dinucleotide (NADH).
respiration refers to two distinct processes. The first is the exchange
of gasses between the bloodstream and the tissues. The second is the
process of cellular respiration, from which cells utilize oxygen to
perform basic metabolic functions.
Gas Exchange with Tissues
exchange occurs in the alveoli so that oxygen is loaded into the
bloodstream and carbon dioxide is unloaded from the bloodstream.
Afterwards, oxygen is brought to the left side of the heart via the
pulmonary vein, which pumps it into systemic circulation.
Red blood cells carry the oxygen into the capillaries of the tissues of the body. Oxygen diffuses into the cells of the tissues, while carbon dioxide diffuses out of the cells of the tissues and into the bloodstream.
The factors that influence tissue gas exchange are similar to the factors of alveolar gas exchange, and include partial pressure gradients between the blood and the tissues, the blood perfusion of those tissues, and the surface areas of those tissues. Each of those factors generally increase gas exchange as those factors are increased (i.e., more oxygen diffusion in tissues with more blood perfusion).
Regarding the partial pressure gradients in systemic capillaries, they have a PaO2 of 100mmHg and a PaCO2 of 40mmHG within the capillary and a PaO2 of 40 mmHg and PaCO2 of 45 mmHg inside issue cells, which allows gas exchange to occur.
Cellular respiration is the metabolic process by which an organism obtains energy through the reaction of oxygen with glucose to produce water, carbon dioxide and ATP, which is the functional source of energy for the cell. The oxygen supply for cellular respiration comes from the external respiration of the respiratory system.
The carbon dioxide waste is the result of the carbon from glucose (C6H12O6) being broken down to produce the pyruvate and NADH intermediates needed to produce ATP at the end of respiration. The energy stored in ATP can then be used to drive processes that
require energy, including biosynthesis, locomotion, or transportation of
molecules across cell membranes.
Cellular respiration can occur anaerobically without oxygen, such as through lactic acid fermentation. Human cells may use lactic acid fermentation in muscle tissue during strenuous exercise when there isn't enough oxygen to power the tissues. This process is very inefficient compared to aerobic respiration, as without oxidative phosphorylation, the cell cannot produce nearly as much ATP (2 ATP compared to 38 during cellular respiration).