Glycolysis

It can be confusing to keep track of what is being oxidized and what is being reduced. Using the phrase "LEO the lion says GER" can help us remember which is which. Looking at the charge of a molecule can also clue you in about where electrons are going. If a molecule is sporting a + sign (such as NAD⁺), that is a good sign that it needs an electron. It will likely be reduced, gain an electron, and become neutrally charged, or not charged at all.

Glycolysis breaks down glucose, so you may think that glucose is the only form of energy acceptable to animals, including humans. On the contrary, glucose is rare in our diets. We eat lots of other sugars despite the dentist's advice, including sucrose, fructose, and lactose, but not a lot of plain old glucose. The good news is that our bodies can convert other compounds into glucose, including proteins and fats.

Glycolysis is presented here as the first step in cellular respiration, which it is. However, it can also exist without the rest of cellular respiration—organisms that undergo fermentation in anaerobic environments undergo glycolysis, too.

Citric Acid Cycle

Because the citric acid cycle makes many different compounds, it is easy to lose track of the main product of the citric acid cycle: energy. The main point of the citric acid cycle is to change pyruvate into ATP, NADH, and FADH₂. Pyruvate that originally came from glucose is oxidized in a series of steps that result in ATP, NADH, and FADH₂. ATP is energy, and NADH and FADH₂ become energy after they go through the electron transport chain.

Fermentation

Anaerobic sounds a little bit too much like aerobic for some people's liking. The aero– part means "oxygen," and an– means "without," so anaerobic means "without oxygen." Just remember: you don't have the guts to do anaerobic respiration, but cow guts do.

Carbon dioxide is only produced in alcohol fermentation, not lactic acid fermentation.