Biochemistry Questions: Amino Acids, Porphyries, and Urea Cycle

Proteins that may be absorbed by the intestine are:
b. Maternal antibodies in newborns
Sources of amino acids in the body include:
1. Degradation of body protein
2. Synthesis of nonessential amino acids
3. Dietary proteins
Enzymes Secreted by Organs
Match the organs (a-d) with the enzymes (A-E) they secrete:
1. Organs:
  1. Stomach: D
  2. Small intestine: E
  3. Liver: (No enzyme listed)
2. Enzymes:
  1. Trypsin – A
  2. Carboxypeptidase A – B
  3. Elastase (No letter)
  4. Pepsin (No letter)
  5. Alanine aminopeptidase (No letter)
Mark the WRONG sentence about the source of ammonia:
a. The formation of ammonia from urine is linked to the action of ukase (This statement is likely incorrect and requires verification)
The correct level of serum ammonia is:
a. 5-50 μmol/L
Completely glucogenic amino acids are:
e. Valine, Aspartate, Cysteine
Phenylketonuria (PKU) is caused by a deficiency of:
a. Phenylalanine hydroxylase

Mark True (T) or False (F) for the following statements about phenylketonuria:

a. Symptoms of the disease are: mental retardation, deficiency of pigmentation, seizures, failure to walk and talk	T/F
b. Is characterized by the accumulation of tyrosine	T/F
c. Symptoms of the disease appear in old age	T/F

A newborn has milky skin, white hair, and red-appearing eye color. This disorder most often results from a defect in which of the following enzymes?
d. Tyrosinase
Mark the WRONG answer:
e. Histidine is a precursor of alanine
Mark the TRUE answer about porphyries:
a. Porphyries are defects in heme synthesis
This is an X-linked, recessive disorder associated with a deficiency of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) and results in the excessive production of uric acid. The name of the disease is:
b. Lesch-Nyhan syndrome
The most common genetic error of amino acid transport is:
c. Cystinuria
Mark the correct answer about jaundice:
d. Obstructive jaundice may be caused by a hepatic tumor
Complete the sentence:
a. Degradation of hemoproteins occurs in the liver and spleen.
A 3-month-old boy of French-Canadian ancestry is seen by the pediatrician for failure to thrive and poor appetite. A physical exam denotes hepatomegaly and yellowing of the eyes. The boy had been vomiting and had diarrhea, and a distinct cabbage-like odor was apparent. This disorder is due to a defect in the metabolism of which of the following amino acids?
c. Tyrosine
A model presents the structure of: Adenine

Mark True (T) or False (F) for the following statements about homocystinuria:

a. Is characterized by red patches on the skin, skeletal abnormalities (long, thin arms and legs), premature arterial disease, displaced lens, and reticular hypotonia	T/F
b. Is caused by a defect in tyrosine synthase	T/F
c. Methionine is elevated in the blood and urine	T/F
d. Can be treated by supplementation with vitamin B6	T/F

Maple Syrup Urine Disease – True or False
Mark True (T) or False (F) for the following statements about maple syrup urine disease:
a. Is an autosomal recessive disorder
T/F
b. A characteristic cabbage-like odor occurs
T/F
c. No clinical symptoms are present
T/F
Alkaptonuria – True or False
Mark True (T) or False (F) for the following statements about alkaptonuria:
a. Dark pigment in urine
T/F
b. Deficiency in homogentisic acid oxidase
T/F
c. Usually no clinical symptoms are present until later in life
T/F
d. Treatment diet low in phenylalanine and tyrosine
T/F
Mark the correct answer:
a. AMP is a ribonucleotide phosphate
Mark the correct answer about inhibitors of purine synthesis:
1. Sulfonamides inhibit bacterial synthesis of folic acid
2. Analogs of folic acid inhibit the formation of tetrahydrofolate
3. Answers a and b are correct
As a final result of the urea cycle are formed:
d. Urea, 2 ADP, 3H₂O
On the scheme (next page), give the names for compounds:
1. Urea
2. Carbamoyl phosphate
3. L-aspartate
4. Fumarate
On the scheme (next page), mark [use *] the stages where ATP is hydrolyzed
1. Carbamoyl phosphate synthetase I: this enzyme uses 2 ATP for the reaction in the mitochondria
2. Argininosuccinate synthetase: this enzyme uses 1 ATP and degrades it to AMP and pyrophosphate

a. Is an autosomal recessive disorder	T/F
b. A characteristic cabbage-like odor occurs	T/F
c. No clinical symptoms are present	T/F

a. Dark pigment in urine	T/F
b. Deficiency in homogentisic acid oxidase	T/F
c. Usually no clinical symptoms are present until later in life	T/F
d. Treatment diet low in phenylalanine and tyrosine	T/F