PHENYLKETONURIA: A METABOLIC DISORDER
Metabolic disorders are genetic diseases that affect the body's ability to perform its normal chemical reactions. Many metabolic disorders result from enzyme defects. Recall that a metabolic pathway is a stepwise sequence of enzyme-mediated reactions. If one enzyme in a metabolic pathway is defective, that enzyme's substrate may accumulate and the pathway may not be completed. This may result in a buildup of harmful substances or a shortage of required molecules.
Activity
In this exercise, you will use the Web links below to gather information about the metabolic disorder phenylketonuria (PKU). Use what you learn to answer the questions at the bottom of the page.
Questions
1. What enzyme is most commonly defective in people with phenylketonuria?
An enzyme called Phenylalanine Hydroxylase
2. What reaction does this enzyme catalyze? (What is the substrate and what product is produced?)
PAH. Without this, a person could develop high levels of phenylalanine in the brain, which could poison neurons and cause mental retardation or epilepsy.
3. Describe the symptoms of phenylketonuria.
Smaller than normal head, mental retardation, epilepsy, musty odor, and lighter skin and hair4. What causes the symptoms of PKU, the lack of a substance or the buildup of one?
Phenylalanine reacts badly with PKU because the hindered enzyme is one of a metabolic nature.5. How common is phenylketonuria? How is it treated?
Metabolic disorders are genetic diseases that affect the body's ability to perform its normal chemical reactions. Many metabolic disorders result from enzyme defects. Recall that a metabolic pathway is a stepwise sequence of enzyme-mediated reactions. If one enzyme in a metabolic pathway is defective, that enzyme's substrate may accumulate and the pathway may not be completed. This may result in a buildup of harmful substances or a shortage of required molecules.
Activity
In this exercise, you will use the Web links below to gather information about the metabolic disorder phenylketonuria (PKU). Use what you learn to answer the questions at the bottom of the page.
Your Genes, Your Health: Phenylketonuria
NSPKU Home Page
Texas Department of Health Genetic Disorders
Phenylketonuria - The Genetics
Questions
1. What enzyme is most commonly defective in people with phenylketonuria?
An enzyme called Phenylalanine Hydroxylase
2. What reaction does this enzyme catalyze? (What is the substrate and what product is produced?)
PAH. Without this, a person could develop high levels of phenylalanine in the brain, which could poison neurons and cause mental retardation or epilepsy.
3. Describe the symptoms of phenylketonuria.
Smaller than normal head, mental retardation, epilepsy, musty odor, and lighter skin and hair4. What causes the symptoms of PKU, the lack of a substance or the buildup of one?
Phenylalanine reacts badly with PKU because the hindered enzyme is one of a metabolic nature.5. How common is phenylketonuria? How is it treated?
It's not very common at all. It's treated by a low-protein diet that is carried out throughout the patient's life.
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