Mannose enters glycolysis by first being phosphorylated by hexokinase. The newly formed mannose-6-phosphate is then isomerized into fructose-6-phosphate by the enzyme phosphomannose isomerase. The sugar is now in a form that can follow the normal glycolytic pathway.

If glucose was not phosphorylated, it would be free to diffuse through the plasma membrane and leave the cell. This situation would not be good for the cell because the reaction cannot continue outside of the cytosol. The negative charge created by the phosphorylation prevents the glucose molecule from crossing the plasma membrane due to the similar charge at the plasma membrane. 

Glycolysis can be divided into two parts: the energy investment phase and the energy payoff phase. The energy investment phase comes first when glucose is phosphorylated twice, requiring the use of two molecules of ATP. After the glucose is split, four molecules of ATP will be made in the final steps. This results in a net gain of two ATP in glycolysis, but ATP must be spent prior to being made.

During glycolysis, a total of two molecules of NAD⁺ are reduced in order to form two NADH molecules. These NAD⁺ molecules need to be regenerated in order for more glycolytic reactions to take place; otherwise, the process would come to a halt. Fermentation takes care of this problem in anaerobic environments by oxidizing excess NADH (since it is no longer utilized in the electron transport chain) into NAD⁺, which is then returned to the cytosol where it can be used again in glycolysis.

Both phases of glycolysis occur in the cytosol of the cell. The products of glycolysis are moved for further processing into the mitochondria, but the conversion of glucose to pyruvate is a cytosolic reaction. 

The initial energy investment required for conversion of one glucose to pyruvate is 2 ATP in the preparatory phase. In the pay-off phase, substrate level phosphorylation produces a total of 4 ATP per initial glucose. 

 and  are the resultant molecules from this conversion, not the inputs.  and  are important molecules in the citric acid cycle, but are not required for this particular oxidation step.  must be reduced to , and coenzyme A is a crucial modulator of these reactions. Thus,  and coenzyme A are the required inputs for the oxidation of pyruvate to acetyl CoA. 

Starch is a complex carbohydrate that is digested by enzymes in the small intestine. These digestive enzymes, called glucosidases, are released by exocrine glands in humans and are involved in breakdown of complex carbohydrates to their individual monomers (glucose). Recall that energy production in cell begins with glycolysis, where a molecule of glucose is metabolized to produce intermediates for subsequent metabolic steps. Cells can’t use starch or glycogen during glycolysis; therefore, the student must add glucosidase to break down starch into individual glucose molecules.

Energy can be produced in anaerobic conditions (like in glycolysis). It might not have a high yield of energy such as aerobic respiration, but the cells can still produce energy when they are oxygen deficient. As mentioned, glycogen is a complex carbohydrate; therefore, adding it without glucosidase will not help facilitate energy production.

Anaerobic metabolism, such as glycolysis and fermentation, occur in the cellular cytoplasm. The products of glycolysis are transported to the mitochondria where they undergo Krebs cycle (in mitochondrial matrix) and oxidative phosphorylation (on the inner mitochondrial membrane). Both Krebs cycle and oxidative phosphorylation require oxygen and are, therefore, called aerobic metabolism.

Glycolysis is an anaerobic process that produces 2 net ATP, 2 pyruvate molecules, and 2 NADH. Pyruvate is a three-carbon molecule. Recall that glucose is a six-carbon molecule; therefore, the six-carbon glucose is broken down to two three-carbon pyruvate molecules. This means that all the carbons in glucose are transferred to the pyruvate molecules. ATP is produced and consumed in glycolysis. There is a total of four ATP molecules synthesized in the glycolysis; however, glycolysis consume two ATP molecules so you get a net of 2 ATP molecules. Finally, glycolysis involves the reduction two  molecules to yield two NADH molecules (not FAD).