From the question stem, we are shown the reaction in which glucose-6-phosphate is transformed into ribulose-5-phosphate. We are then asked to determine which type of reaction is occurring in this process.

We can also notice from the reaction that  is a reactant, and  is a product. Therefore, the  is being reduced to form . In order for this reduction reaction to happen, there needs to be a simultaneous oxidation reaction occurring, since the electrons need to come from somewhere. In this case, the electrons are coming from glucose-6-phosphate. Therefore, as  is reduced to , glucose-6-phosphate is oxidized to ribulose-5-phosphate. Thus, this is an oxidation reaction.

Also, it's important to note that this is not a carboxylation reaction. In fact, it is actually a decarboxylation reaction, since one of the carbon atoms on glucose is converted into carbon dioxide.

Moreover, this is also not a phosphorylation reaction, as the reactant and products have an equal number of phosphate groups.

And lastly, this is not an isomerization reaction because glucose-6-phosphate and ribulose-5-phosphate have different molecular formulas, thus they cannot ever be structural isomers.

Oxaloacetate is a metabolite of the citric acid cycle, which takes place in the mitochondrial matrix. Oxaloacetate cannot diffuse across the mitochondrial matrix, but malate can. So oxaloacetate is reduced to malate by malate dehydrogenase, and can now enter into the cytoplasm. Since malate dehydrogenase can catalyze the reverse reaction as well as the forward reaction, it can be used again to reform oxaloacetate. Once in the cytoplasm, oxaloacetate is converted into phosphoenolpyruvate (PEP) and continues gluconeogenesis.

Glucose is converted into glycogen during the process called glycogenesis. Its structure consists of many linear alpha(14) glycosidic bonds, and also many branched alpha(16) glycosidic bonds. This heavily-branched structure means that there are many free ends, which are the substrates for glycogen phosphorylase. A debranching enzyme is needed to lyse the alpha(16) glycosidic bonds. Cellulose is a polymer glucose linked together via of beta(14) glycosidic bonds. Humans lack enzymes to catalyze the lysis of these bonds in cellulose.

For each    molecule converted into carbohydrate, 3 ATPs and 2 NADPHs are consumed. The Calvin cycle is initiated when  and ribulose 1,5 biphosphate combine. The enzyme ribulose biphospate carboxylase catalyzes the reaction in the stroma of chloroplasts, and is considered one of the most the world's most abundant proteins. Glyceraldehyde 3-phosphate, which is a by-product of the cycle, goes on to be a building block of sugar, fatty acid, and amino acid synthesis.

The major distinction between NADH and NADPH is that NADH is generally used in catabolic reactions meant to produce ATP.  NADPH, on the other hand, is used primarily in anabolic reactions meant to build macromolecules from their smaller parts.

Gluconeogenesis is the production of glucose from other sources than carbohydrates, such as  from pyruvate, amino acids, lactate and glycerol. Phosphoenolpyruvate carboxykinase converts oxaloacetate to phosphoenolpyruvate and carbon dioxide. It also produces GDP from GTP. It is regulated by hormones, such as glucagon and cortisol.

Aspartate can form arginosuccinate, which can then release a fumarate molecule. The fumarate can enter into the Krebs cycle and eventually the pathway can lead to gluconeogenesis. The arginine from the arginosuccinate can continue through the urea cycle.

UDP-glucose is the activated form of glucose that works to build chains of glycogen. The other listed molecules do not serve this function.

Ingestion of high amounts of ethanol leads to increased NADPH. High levels of NADPH inhibit gluconeogenesis followed by low glucose levels in the absence of dietary intake. In acute ingestion of alcohol, hypoglycemia (low levels of glucose in the blood) can follow due to inhibition of gluconeogenesis.

The pentose phosphate pathway produces NADPH and five-carbon sugars. The net reaction is:

The pathway is also important in purine precursor synthesis.