If you choose to study microbiology at University, you may be involved with experiments such as this, working in an anaerobic chamber. When you exclude oxygen from the environment, respiration takes place anaerobically – without oxygen. Read more here. Anaerobic respiration is used both in the brewing and baking industries, as alcohol and carbon dioxide are produced when specific organisms respire without oxygen. This is called fermentation. If you have access to YouTube, you can see a quick Food Science video about fermentation here.
This site, from Thomas M. Terry of the University of Connecticut, has some excellent, very detailed animations of cellular respiration. Chapter three also deals with enzymes – proteins that accelerate biological reactions. It is important to remember that enzymes are not reactants or products of a reaction – they are not ‘used up’ during the process. Enzymes facilitate, or speed up, a specific reaction. For a good tutorial check out: “What is an Enzyme?”.