7. Using the respirometer-manometer, you observed the amount of oxygen being used by animals in a closed chamber. What happened to the carbon dioxide the animals produced while in the chamber?
Most organisms use molecular oxygen in a process calledcellular respiration. In this series of reactions, the glucosemolecule is completely disassembled to yield CO2and H2O. The process begins withglycolysis; the end product of glycolysis, pyruvate, enters themitochondrion where it is further metabolized.
After entering the mitochondrion, the pyruvate loses aCO2 molecule to form acetyl CoA, whichenters a series of reactions known as the Kreb’s cycle orcitric acid cycle where it is completely oxidized toCO2. The electrons released during thisseries of reactions are used to reduceNAD+, and a related molecule FAD, to NADHand FADH, respectively. These electron carriers then transfer theirelectrons to the electron transport chain (ETC), a series ofproteins embedded in the inner membrane of the mitochondrion. Thepassge of electrons through the ETC generates anH+ gradient across the inner membranewhich drives the synthesis of ATP by ATP synthetases embedded inthe inner membrane. The last electron carrier protein in the ETCtransfers the electrons to molecular oxygen to form water, with theaddition of H+. This transfer ofelectrons to oxygen returns the protein (cytochrome oxidase) to itsoxidized state so that it can continue to accept electrons from theremainder of the ETC.
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