Question

Zellweger syndrome is one of a class called Peroxisome Biogenesis Disorders (PBD). PBDs are characterized by abnormalities of the liver, kidney, brain, and skeletal system. Zellweger syndrome is particularly severe and death usually occurs by age 6 months. There is an absence of functional peroxisomes. Peroxisomes have a role in all of the following except A. oxidation of very long chain fatty acids. B. synthesis of glycerolipids. C. hydrolysis of cholesteryl esters. D. oxidation of D-amino acids. E. oxidation of uric acid.

Short answer

A) Oxidation of very long chain fatty acids B) Synthesis of glycerolipids C) Degradation of purines D) Detoxification of reactive oxygen species (ROS) E) Oxidation of uric acid Answer: E) Oxidation of uric acid

Step-by-step solution

Understand the roles of peroxisomes

Peroxisomes are organelles found in cells and they have various roles, including the breakdown and synthesis of important molecules. Familiarize yourself with these roles by reviewing your study materials or conducting research.

Eliminate options that are performed by peroxisomes

Based on your understanding of peroxisomes' roles, eliminate the options that correspond to the functions commonly performed by peroxisomes. For example, you might find that peroxisomes are involved in the oxidation of very long chain fatty acids (option A) and the synthesis of glycerolipids (option B). In this case, you would eliminate these options from consideration.

Identify the option that is NOT a function of peroxisomes

After eliminating options that are performed by peroxisomes, you should be left with one or two options. Review these options and, if needed, conduct further research to determine which one is NOT a function of peroxisomes. This will be the correct answer to the question.

Select the correct answer

Based on your evaluation of the options and elimination of those that are functions of peroxisomes, select the correct answer. In this case, the correct answer is E. oxidation of uric acid, as it is NOT a function of peroxisomes.

Key concepts

Zellweger Syndrome

Zellweger syndrome is a life-threatening genetic disorder that affects infants, characterized by the absence of functional peroxisomes in the cells. This syndrome falls under a larger group of diseases known as Peroxisome Biogenesis Disorders (PBD).

Infants with Zellweger syndrome display a wide range of developmental issues, predominantly affecting the liver, kidneys, brain, and skeletal system. Sadly, this condition is severe, and affected individuals typically do not survive beyond six months of age. One of the main reasons for the critical nature of Zellweger syndrome is that peroxisomes play an essential role in various biochemical processes in the body. Without functional peroxisomes, toxic substances accumulate and vital compounds are not synthesized adequately, which leads to the dysfunction of multiple organ systems.

Peroxisome Functions

Peroxisomes are small, membrane-bound organelles present in virtually all eukaryotic cells. They are critically involved in a variety of cellular processes, particularly those related to lipid metabolism and the detoxification of harmful substances.

Lipid Metabolism

In the context of lipid metabolism, peroxisomes are involved in the oxidation of very long chain fatty acids, which cannot be processed by mitochondria. This breakdown process, known as beta-oxidation, is crucial for energy production and the synthesis of myelin, which insulates nerve cells.

Detoxification

Peroxisomes also play a key role in detoxifying compounds, such as hydrogen peroxide, by converting them into water and oxygen through the action of the enzyme catalase. This process helps protect the cell from oxidative damage.

Additionally, peroxisomes are involved in the biosynthesis of plasmalogens, which are important for the normal function of the brain and lungs. They also contribute to the synthesis of bile acids and cholesterol, which are vital for digestion and hormone production, respectively.

Biochemical Pathways

Biochemical pathways are series of chemical reactions occurring within a cell that lead to the transformation of one molecule into another. These pathways are essential for maintaining life processes, as they are involved in the synthesis and breakdown of compounds critical to cell function.

Peroxisomes play a pivotal role in several biochemical pathways. For instance, they house enzymes essential for the oxidation of fatty acids, the synthesis of certain lipids, and the disposal of reactive oxygen species. Moreover, they are involved in the synthesis of cholesterol and other important lipids, which form cell membranes and serve signaling functions.

The malfunction of these pathways, as seen in peroxisome biogenesis disorders, results in the accumulation of toxic substances and deficiency in critical lipids, leading to the severe symptoms and outcomes associated with diseases like Zellweger syndrome. Because peroxisomes are not present to carry out these metabolic reactions, key aspects of cellular function are disrupted, causing profound effects on the health and development of affected individuals.