Question 1

Which of the following amino acids becomes conditionally essential for those with urea cycle disorders, and thus should be supplemented in their diet?

Accepted Answer

Those with urea cycle disorders have impaired ability to convert ammonia to urea, leading to high levels of ammonia in the blood which can be toxic. Arginine is a precursor to urea production and becomes conditionally essential in individuals with such disorders. Therefore, it is important to supplement arginine in their diet to support the urea cycle and prevent toxic build-up of ammonia. Arginine becomes conditionally essential for those with urea cycle disorders as they are unable to convert ammonia to urea efficiently. Therefore, it should be supplemented in their diet.

Question 2

Approximately one out of every _____ children born will have an inborn error of metabolism

Accepted Answer

According to current estimates, approximately one out of every 2,500 to 5,000 newborns in the United States is diagnosed with an inborn error of metabolism. According to current estimates, approximately one out of every 2,500 children born will have an inborn error of metabolism.

Question 3

Urea cycle disorders result from an impaired capacity of the body to excrete _____ in the form of urea

Accepted Answer

Urea cycle disorders occur when there is a defect in one of the enzymes responsible for converting nitrogen into urea, which can be excreted by the body. As a result, there is a buildup of nitrogen-containing compounds such as ammonia, which can be toxic to the body. Urea cycle disorders result from a deficiency or dysfunction of one of the enzymes involved in the urea cycle, which is responsible for converting toxic ammonia to urea for excretion. This leads to the accumulation of nitrogen in the form of ammonia, which can be neurotoxic and cause a range of symptoms.

Question 4

Which metabolic disorder is tested and screened for in newborns in all 50 US states?

Accepted Answer

Phenylketonuria (PKU) is the metabolic disorder that is tested and screened for in newborns in all 50 US states. This condition impairs the body's ability to process an amino acid called phenylalanine, which can lead to brain damage and intellectual disability if not managed through a specific diet. Early detection through newborn screening allows for early treatment and prevention of these negative outcomes. Phenylketonuria (PKU) is the metabolic disorder that is tested and screened for in newborns in all 50 US states. This is because early detection and treatment of PKU can prevent severe intellectual disability and other serious health problems.

Question 5

Which of the following is not a result of untreated PKU?

Accepted Answer

Untreated PKU can lead to mental retardation, seizures, and eczema. However, it does not result in obesity. Untreated PKU can lead to mental retardation, seizures, and eczema due to the buildup of phenylalanine in the body. However, obesity is not typically associated with untreated PKU.

Question 6

With autosomal recessive inheritance, what is the probability that carrier parents will have an affected child with each pregnancy?

Accepted Answer

With autosomal recessive inheritance, carrier parents have a 25% chance of having an affected child with each pregnancy. This is because both parents are carriers of the affected gene and each parent has a 50% chance of passing on the mutated gene to their offspring. Therefore, the probability of both parents passing on the mutated gene to their child is 50% x 50% = 25%. With autosomal recessive inheritance, carrier parents have a 25% chance with each pregnancy of having an affected child, a 50% chance of having a carrier child, and a 25% chance of having an unaffected, non-carrier child. This is because each parent has a 50% chance of passing on the recessive disease gene, and in order for the child to be affected, both parents must pass it on.

Question 7

In galactosemia the defective enzyme, uridyltransferase, is responsible for converting _____

Accepted Answer

In galactosemia, the defective enzyme uridyltransferase is responsible for converting galactose-1-phosphate to glucose-1-phosphate. This results in a buildup of galactose-1-phosphate in the body, leading to the harmful effects of galactosemia. The defective enzyme in galactosemia is uridyltransferase which is responsible for converting galactose-1-phosphate to glucose-1-phosphate. This leads to an accumulation of galactose-1-phosphate which can cause damage to various organs and tissues in the body.

Question 8

For best utilization of synthetic amino acids, one should:

Accepted Answer

Consuming smaller quantities of synthetic amino acids 4 to 5 times per day allows for better absorption and utilization by the body. Consuming a large quantity at once may cause the body to excrete excess amino acids rather than utilizing them for muscle growth and repair. Dividing the intake into smaller amounts throughout the day ensures a steady supply of amino acids to the muscles. Consuming smaller quantities of synthetic amino acids 4 to 5 times per day is the best choice. This allows for a consistent supply of amino acids for protein synthesis throughout the day, rather than just one or two large doses.

Question 9

The urea cycle resides primarily in the:

Accepted Answer

The urea cycle takes place primarily in the liver (hepatocytes) where ammonia is converted into urea and then transported to the kidneys for excretion. The urea cycle, which is responsible for converting toxic ammonia into less toxic urea, primarily occurs in hepatocytes (liver cells).

Question 10

In glycogen storage disease type I, the enzyme block results in an inability to produce:

Accepted Answer

In glycogen storage disease type I, the enzyme block affects the production of glucose. Glucose cannot be produced from glycogen stores in the liver, and this leads to low blood sugar levels (hypoglycemia) and other complications. Galactose and fructose are not directly affected by this type of glycogen storage disease. In glycogen storage disease type I, the enzyme block occurs in glucose-6-phosphatase, which is responsible for converting glucose-6-phosphate to glucose. As a result, there is an inability to produce glucose, leading to hypoglycemia and other metabolic disturbances. The inability to produce glycogen is a secondary effect of the block in glucose production. Galactose and fructose production are not affected in this type of glycogen storage disease.

Question 11

Which of the following is not an example of selective neonatal screening?

Accepted Answer

Selective neonatal screening involves testing only certain infants based on risk factors such as family history, ethnicity, or clinical presentation. Testing all infants in a population is not selective and is known as universal neonatal screening. Selective neonatal screening involves targeting specific groups of infants who are at higher risk for certain genetic conditions, based on factors such as family history, ethnicity, or geographic location. Testing all infants in a population would be considered universal screening, which is not an example of selective screening.

Question 12

A block in the urea cycle can result from a deficiency in any of these enzymes except:

Accepted Answer

Glucokinase is not involved in the urea cycle, so a deficiency in this enzyme would not result in a block in the cycle. Deficiencies in the other enzymes listed can lead to a block in the urea cycle. Glucokinase is not a part of the urea cycle and therefore its deficiency will not result in a block in the urea cycle. Deficiencies in carbamyl phosphate synthetase I, arginase, and argininosuccinic acid lyase can all lead to a block in the urea cycle.

Question 13

In order for individuals with PKU to obtain the necessary amount of protein that they need to promote adequate growth, they are required to:

Accepted Answer

Individuals with PKU need to avoid phenylalanine and supplement their diet with protein that is low in phenylalanine. Therefore, a protein supplement containing all the amino acids except for phenylalanine would be the best choice. Individuals with PKU cannot properly metabolize phenylalanine, which is found in most dietary proteins. Therefore, they need to consume a protein supplement that contains all the essential amino acids except phenylalanine to avoid buildup of this amino acid in their body. Consuming meats and beans twice a day may not be enough to provide adequate protein intake, as they may not contain the correct balance of amino acids needed. Capsules containing all the amino acids may contain phenylalanine and are not recommended for individuals with PKU. A protein supplement containing at least 50 grams of protein per day may not be necessary for all individuals with PKU and should be determined by a healthcare professional based on individual needs.

Question 14

Glycogen storage disease type I is due to a deficiency of the _____ enzyme, which results in _____

Accepted Answer

Glycogen storage disease type I is due to a deficiency of the glucose-6-phosphatase enzyme, which is necessary for the final step in gluconeogenesis and glycogenolysis to release glucose from glycogen stores. Without this enzyme, there is impaired glucose production and hypoglycemia. Therefore, option B is the correct choice. Glycogen storage disease type I is due to a deficiency of the glucose-6-phosphatase enzyme, which results in hypoglycemia.

Question 15

In phenylketonuria, the deficiency or absence of the phenylalanine hydroxylase enzyme leads to into the inability to convert phenylalanine into which amino acid?

Accepted Answer

In phenylketonuria, there is a deficiency or absence of the phenylalanine hydroxylase enzyme, which leads to the inability to convert phenylalanine into tyrosine. This results in a buildup of phenylalanine in the body and a deficiency of tyrosine. Phenylketonuria is caused by the deficiency or absence of the phenylalanine hydroxylase enzyme, which is responsible for converting phenylalanine into tyrosine. Without this enzyme, phenylalanine accumulates in the body and can cause neurological problems.

Question 16

The etiology of inborn errors of metabolism can best be described as:

Accepted Answer

Inborn errors of metabolism result from a genetic error in the flow of metabolic pathways. This includes defects in the enzymes responsible for biochemical reactions, transport proteins, and regulatory elements. These defects can lead to a buildup of toxic metabolites, a deficiency of essential metabolites, or both. Inborn errors of metabolism are genetic errors in metabolic flow, meaning there is an error in the way that certain metabolic pathways function due to a genetic mutation. This can lead to a lack of enzymes or substrates, as well as other types of metabolic dysfunction, but ultimately the root cause is a genetic error. Defective transport of amino acids may be a symptom of certain inborn errors of metabolism, but it is not the underlying cause.

Question 17

The treatment of an amino acid disorder involves:

Accepted Answer

Restricting dietary protein intake is the best choice for treating an amino acid disorder as it helps to control the levels of the affected amino acid in the body. Complete cessation of protein intake is not recommended as it can lead to malnutrition and other health complications. Maintaining normal dietary servings of protein or increasing protein content can exacerbate the condition. Restricting dietary protein intake is the best choice for the treatment of an amino acid disorder. This is because the disorder results in the body's inability to metabolize or break down specific amino acids. As a result, these amino acids can accumulate and cause harm to the body's cells and organs. By limiting the intake of proteins that contain the affected amino acids, the body can better manage the disorder and prevent the harmful effects of amino acid buildup.

Question 18

Which of the following nutrients are individuals with galactosemia most likely to be deficient in?

Accepted Answer

Individuals with galactosemia often avoid dairy products, which are primary sources of calcium and vitamin D, leading to potential deficiencies in these nutrients.

Question 19

Which of the following urea cycle enzyme deficiencies is inherited as an X-linked dominant trait that is usually lethal in males?

Accepted Answer

Ornithine transcarbamylase deficiency is an X-linked dominant trait. Males with this deficiency usually die within the first few days of life. Females who inherit the mutation can have variable symptoms depending on the degree of X-inactivation in affected tissues. Ornithine transcarbamylase deficiency is an X-linked dominant trait that is usually lethal in males. The other options (A, B, D) are all inherited in an autosomal recessive manner.

Question 20

Those with fructose intolerance should avoid which of the following sugars?

Accepted Answer

Fructose intolerance means the body cannot properly process fructose, sucrose is made up of fructose and glucose, and sorbitol is a sugar alcohol that can also be difficult to digest for those with fructose intolerance. Therefore, those with fructose intolerance should avoid fructose, sucrose, and sorbitol. Fructose intolerance means the body cannot properly absorb and digest fructose, sucrose (which is made up of fructose and glucose), and sorbitol (a sugar alcohol). Therefore, those with fructose intolerance should avoid all three sugars. The other options include at least one of the sugars that should be avoided.

Quiz 26: Metabolic Disorders