Converts glucose into pyruvate, creating ATP and NADH along the way. It's the first "chunk" of respiration and happens in both aerobic and anaerobic respiration. It occurs in the cytosol and has a prepatory (investment) phase where ATP (I think 2?) is consumed, and in the end, 4 is produced. No actual oxygen is spent during this time; it's just a giant string of enzyme-run reactions.