Glycolysis is the first step taken in cellular respiration and takes place in the cytoplasm while pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation take place inside the mitochondria.

Glycolysis creates ATP and NADH through substrate level phosphorylation. The net products are 2 ATP, 2 NADH, and 2 pyruvate molecules. More ATP and high energy electron carriers are produced in the subsequent stages of the metabolic pathway such as pyruvate processing and the citric acid cycle. 

Glycolysis starts with the break down of one molecule of glucose via energy input from  to form 2 molecules of , 4 molecules of , 2 pyruvate molecules, and  molecules. This step will continue regardless of whether oxygen is present or not.

Without oxygen the final two steps of cellular respiration (Citric acid cycle and oxidative phosphorylation) can not be performed because it is used as the final electron acceptor. However, the first step, glycolysis produces a small amount of energy in the form of ATP as well as pyruvate and NADH. NADH can be recycle (to be used again in another round of glycolysis) by converting pyruvate to lactic acid. This process is known as lactic acid fermentation. 

Catabolic reactions are those that breakdown organic molecules into smaller molecules and release energy. Glycolysis involves the breakdown of glucose into pyruvate, , and . Citric acid cycle is a series of reaction that take acetyl-CoA and oxaloacetate and produce carbon dioxide, , , and . Thus, the Krebs cycle is both catabolic and anabolic. Photosynthesis and protein synthesis are both anabolic reactions. In contrast, while oxidative phosphorylation does produce energy in the form of , is neither catabolic nor anabolic because it simply transfers energy in the form of the electron carrier into  and does breakdown or produce organic molecules.

Per glucose only  is generated in substrate level phosphorylation in glycolysis. Additionally only  is produces per glucose in glycolysis. However the 2 pyruvate that are produced by glycolysis make  and  (along with ) during the citric acid cycle.

Oxygen is neither a product nor reactant in glycolysis. Glycolysis is unique in that it takes place within the cytoplasm of the cell and does not require oxygen. It is an anaerobic reaction that produces pyruvate, NAD, and ATP. Know the products and reactants of glycolysis.

The correct answer to this question is glycolysis.

We can know this if we remember that glycolysis is a ten step anaerobic, not aerobic pathway that uses the 6 carbon sugar known as glucose and converts it to 2 pyruvate molecules. All of the other answers do not use glucose and convert it to pyruvate. 

The correct answer to this question is carbon dioxide.

Carbon dioxide is not produced during glycolysis. Remember in glycolysis one glucose molecule yields 2 pyruvate, 2 ATP, and 2 NADH. Heat is also given off in form of energy as we went over before. Carbon dioxide is involved in other processes.

The correct answer to this question is glycolysis and fermentation.

Glycolysis and fermentation occur in the cytosol of a eukaryotic cell. Chemiosmosis occurs in the inner mitochondrial membrane and thylakoid membranes of chloroplasts in eukaryotes. The citric acid cycle occurs in the mitochondrial matrix. Oxidative phosphorylation occurs in the mitochondria so the answer has to be glycolysis and fermentation