Metabolism
on-line - the virtual tutorial room
copyright © 2008 - 2015 David A Bender
A respiratory physiology practical class - and beyond
Key points from this exercise:
Oxygen is consumed in the oxidation of metabolic fuels to carbon dioxide and water.
Oxidation can occur by:
removal of hydrogen (hydrogen ions plus electrons)
removal of electrons
addition of oxygen from oxygen itself or from water.
Most metabolites are oxidised by removal of hydrogen onto an intermediate hydrogen carrier (a coenzyme).
The water formed by the oxidation of metabolic fuels is known as metabolic water. Total water loss from the body is about 350 mL greater than water intake.
A metabolic pathway is a series of enzymes catalysing reactions, in which the product of one enzyme acts as the substrate of the next.
Unidirectional flux through a pathway, even when all the enzymes are readily reversible, can be ensured by providing a constant source of the starting substrate, or, more commonly, by removing one or more of the products of the pathway.