Match the following vocabulary with the definitions. 1. occurring in the presence of oxygen glycolysis 2. the stage of respiration that occurs in anaerobic condition in animal cells lactic acid fermentation 3. the first step in the chemical breakdown of glucose anaerobic 4. occurring in the absence of oxygen aerobic 5. the stage of respiration that occurs in anaerobic conditions in less complex organisms alcohol fermentation

1. aerobic

2. lactic acid fermentation

3. glycolysis

4. anaerobic

5. alcohol fermentation

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.