Glycolysis is the first step of cellular respiration, and creates molecules of ATP, pyruvate, and NADH. FADH₂ is produced later, during the citric acid cycle. Both NADH and FADH₂ serve as electron carriers, depositing electrons in the electron transport chain to generate the proton gradient that powers ATP synthase.

This question requires you to determine where aerobic and anaerobic respiration diverge in terms of a biochemical pathway. Both start with glucose, which undergoes glycolysis in both pathways. The completion of glycolysis results in two molecules of pyruvate, regardless of the availability of oxygen. Once pyruvate is created, it can do one of two things:

1. It can be converted to acetyl-CoA and enter the citric acid cycle (aerobic respiration).

2. It can be reduced to ethanol or lactic acid (anaerobic).

As a result, pyruvate's ultimate path is what determines whether the cell will be using aerobic or anaerobic respiration.

Glycolysis is the first step of cellular respiration and, in the process of splitting glucose into two pyruvate molecules, does not require oxygen.

Pyruvate decarboxylation, the citric acid cycle, and oxidative phosphorylation are all steps in aerobic respiration, and thus require the presence of oxygen.

Catabolic pathways release energy by breaking down complex molecules. Anabolic pathways build molecules from simpler ones.

Glycolysis creates a net phosphorylation of 2  in the process of breaking down a glucose into a pyruvate while converting 2  into 2 . Without , glycolysis cannot be used to make , and the purpose of fermentation is to replenish the needed .

The net production of ATP is 2. 

This is because for glycolysis to occur, 2 ATP must be used. Glycolysis goes on to produce 4 ATP. The loss of 2 ATP and the gain of 4 ATP results in a total net gain of 2 ATP molecules. Note that the ATP produced during glycolysis are via substrate level phosphorylation.

Glycolysis is an anaerobic process that occurs in the cytosol or the cytoplasm of the cell. This process does not require any organelles to take place. The mitochondria is where the Krebs cycle and the electron transport chain occur.

The Krebs cycle and the electron transport chain are both aerobic processes, meaning that they do require oxygen to require. Glycolysis, on the other hand, is an anaerobic process and does not need oxygen to proceed.

The oxidizing agent is the item that gets reduced, meaning it gains electrons. The only item here that gains electrons during the process of fermentation is .  becomes reduced to  by gaining electrons. Recall OIL RIG - oxidation is loss of electrons and reduction is gain of electrons.

Lactic acid, ethanol,  and  are not oxidizing agents in fermentation.

Glycolysis is a catabolic process that produces ATP. A catabolic process degrades molecules, releasing energy, whereas an anabolic process requires energy to synthesize larger biomolecules. It takes energy to create a bond, but when a bond is broken, energy is released. ATP, not GTP, is produced from glycolysis; however, GTP is produced during the citric acid cycle. Cyclic AMP is an intracellular secondary messenger involved in signal transduction.