Question

There is a reaction in carbohydrate metabolism in which glucose- 6 -phosphate reacts with \(\mathrm{NADP}^{+}\) to give 6 -phosphoglucono- 8 -lactone and NADPH. In this reaction, which substance is oxidized, and which is reduced? Which substance is the oxidizing agent, and which is the reducing agent?

Short answer

Glucose-6-phosphate is oxidized and is the reducing agent. \( \text{NADP}^{+} \) is reduced and is the oxidizing agent.

Step-by-step solution

Identify the reaction components

The reaction provided is: glucose-6-phosphate + \(\text{NADP}^{+} \) -> 6-phosphoglucono-8-lactone + NADPH. Identify the substances involved in the reaction and their roles: glucose-6-phosphate, \(\text{NADP}^{+}\), 6-phosphoglucono-8-lactone, and NADPH.

Determine the oxidation states

Understand the reaction process: \(\text{NADP}^{+}\) gains electrons (is reduced) to form NADPH, while glucose-6-phosphate loses electrons (is oxidized) to form 6-phosphoglucono-8-lactone.

Determine the oxidized and reduced substances

In this reaction, glucose-6-phosphate is oxidized (loses electrons) to form 6-phosphoglucono-8-lactone. \(\text{NADP}^{+}\) is reduced (gains electrons) to form NADPH.

Identify the oxidizing and reducing agents

The substance that gets reduced (\(\text{NADP}^{+}\)) is the oxidizing agent because it accepts electrons. Conversely, the substance that gets oxidized (glucose-6-phosphate) is the reducing agent because it donates electrons.

Key concepts

glucose-6-phosphate

Glucose-6-phosphate plays a vital role in carbohydrate metabolism. It's an important molecule derived from glucose, a form of sugar that our bodies use for energy. When glucose enters the cell, it's often quickly converted to glucose-6-phosphate. This helps trap glucose inside the cell, making it available for further metabolic processes.

In the specific reaction mentioned, glucose-6-phosphate undergoes oxidation. This means it loses electrons. It transforms into a new compound called 6-phosphoglucono-8-lactone. The oxidation of glucose-6-phosphate is a key step in various metabolic pathways, including glycolysis and the pentose phosphate pathway.

Glycolysis breaks down glucose for energy, while the pentose phosphate pathway generates NADPH and ribose-5-phosphate, which are crucial for biosynthesis and antioxidant defense.

NADP+

NADP+, or nicotinamide adenine dinucleotide phosphate, is a coenzyme involved in many biochemical reactions. It's essential for various cellular processes, especially in carbohydrate metabolism. NADP+ acts as an electron acceptor. When it gains electrons, it gets reduced to NADPH.

In the context of the reaction with glucose-6-phosphate, NADP+ is the substance that gets reduced. This means it accepts electrons that glucose-6-phosphate loses. By accepting these electrons, NADP+ itself transforms into NADPH.

This transformation is significant because NADPH plays several crucial roles in the cell, including being a reducing agent in biosynthetic reactions and helping in antioxidant defense by maintaining glutathione in its reduced form.

oxidation-reduction

Oxidation-reduction reactions, also known as redox reactions, involve the transfer of electrons between two substances. One substance loses electrons (oxidation), while another gains electrons (reduction). These reactions are fundamental in metabolism and energy production.

In the reaction under discussion, glucose-6-phosphate is the substance that gets oxidized. Oxidation here means it loses electrons. On the other hand, NADP+ gets reduced, meaning it gains the electrons lost by glucose-6-phosphate.

Because NADP+ gains electrons, it's the oxidizing agent. This is because it enables the oxidation of glucose-6-phosphate by accepting its electrons. Conversely, glucose-6-phosphate serves as the reducing agent since it donates electrons to NADP+, facilitating its reduction to NADPH.

Understanding redox reactions is crucial in biochemistry because they drive essential processes like cellular respiration, photosynthesis, and detoxification.