Question

\(\alpha\) -Oxidation A. is important in the metabolism of branched chain fatty acids. B. metabolizes a fatty acid completely to acetyl CoA. C. produces hydrogen peroxide. D. prevents the fatty acid from producing energy. E. requires NADPH.

Short answer

Answer: C. produces hydrogen peroxide.

Step-by-step solution

Statement A: Importance in the metabolism of branched chain fatty acids.

α-oxidation is indeed an important metabolic pathway for processing branched chain fatty acids, as it shortens them during metabolism by removing a single carbon atom so that beta-oxidation can occur.

Statement B: Metabolizes fatty acids completely to acetyl CoA.

This statement is not true. α-oxidation does not completely metabolize a fatty acid to acetyl CoA; instead, it processes branched-chain fatty acids so that the primary process for breaking down fatty acids, beta-oxidation, can occur.

Statement C: Produces hydrogen peroxide.

This statement is true. α-oxidation involves the removal of a single carbon atom from the fatty acid, which generates hydrogen peroxide (H2O2) as a byproduct. The hydrogen peroxide is then detoxified by the enzyme catalase.

Statement D: Prevents the fatty acid from producing energy.

This statement is not true. α-oxidation does not prevent the fatty acid from producing energy; instead, it prepares branched-chain fatty acids for subsequent metabolism via beta-oxidation, which in turn generates energy in the form of ATP.

Statement E: Requires NADPH.

This statement is not true. α-oxidation does not require NADPH as a cofactor. Instead, it requires molecular oxygen and the enzymes known as hydroxylases and thiolases to catalyze the process. Based on the evaluation of each statement, the true statement about α-oxidation is: C. produces hydrogen peroxide.

Key concepts

Metabolism of Branched Chain Fatty Acids

Understanding the metabolism of branched chain fatty acids is pivotal for a comprehensive view of human biochemistry. These fatty acids, which have a branch in their carbon chain, cannot be processed through the regular pathway of beta-oxidation without prior modification. That's where α-oxidation comes into play. In α-oxidation, the pathway targets the removal of one carbon from the carboxyl end of the fatty acid. This process facilitates the metabolism of branched chain fatty acids by converting them into a form that can be further broken down by beta-oxidation.

During α-oxidation, the enzyme involved first oxidizes the alpha carbon, which is the second carbon atom next to the carboxyl group of the fatty acid. This is followed by decarboxylation, where a carbon atom is removed from the fatty acid chain. After this step, the altered fatty acid can enter beta-oxidation, a primary metabolic pathway to generate acetyl CoA, the molecule that enters the citric acid cycle for energy production.

An example of a branched chain fatty acid is phytanic acid, which is broken down by α-oxidation. Defects in this process can lead to the accumulation of such fatty acids, which is observed in some metabolic disorders, such as Refsum disease.

Biochemical Pathways

Biochemical pathways are sequences of chemical reactions occurring within a cell. These pathways are how cells process nutrients to harness energy, build new compounds, and regulate biological functions. In the context of fatty acid metabolism, α-oxidation is a specific biochemical pathway that is essential for the metabolism of certain fatty acids.

α-oxidation differs from the more well-known process of beta-oxidation. While beta-oxidation removes two carbon atoms at a time from the acyl end of a fatty acid chain to produce acetyl CoA until the entire chain is converted, α-oxidation deals with the initial shortening of branched chain fatty acids. This allows for the subsequent action of beta-oxidation on fatty acids that would otherwise not fit into the standard degradation pathway due to their branch points.

The orderly flow through these pathways ensures that energy is produced efficiently within the cell. Any disruption in these intricate systems, such as a block in a pathway due to genetic mutations or metabolic inhibitors, can have significant effects on the organism's homeostasis and overall health.

Hydrogen Peroxide Production

One critical aspect of certain biochemical reactions is the generation of byproducts. In the case of α-oxidation, hydrogen peroxide (H₂O₂) is produced as a byproduct. Hydrogen peroxide is a reactive oxygen species, which at higher concentrations, can be harmful to the cell because it can cause oxidative damage to proteins, lipids, and DNA.

The body is equipped with mechanisms to handle these potentially dangerous compounds. An enzyme called catalase is present in the peroxisomes, cellular organelles that are abundant in liver and kidney cells. Catalase quickly converts hydrogen peroxide into water (H₂O) and oxygen (O₂), significantly reducing its toxicity and protecting the cell from oxidative stress.

This detoxification is essential, as it keeps the balance between the necessary biochemical reactions for metabolism and the protection against cellular damage. The production and subsequent detoxification of hydrogen peroxide in α-oxidation highlight the body's intricate control systems that maintain cellular health despite the complex nature of metabolic processes.