Description
- Which one of the following statements about amino acids and their metabolism is correct;
- Free amino acids are taken into the enterocytes by a proton-linked transport system
- Liver uses ammonia to buffer protons
- Muscle-derived glutamine is metabolized in liver and kidney tissue to ammonia plus α – ketoglutarate
- The toxic ammonia generated from the amide nitrogen of amino acids is transported through blood as arginine
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Explanation & Answer
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Introduction to Biochemistry (SCI 260)
Final Exam
Quarter 3, 2020
Instructor’s name: Mustafa Qasim
Student’s Name:
1. Which one of the following statements about amino acids and their metabolism is correct;
a. Free amino acids are taken into the enterocytes by a proton-linked transport system
b. Liver uses ammonia to buffer protons
c. Muscle-derived glutamine is metabolized in liver and kidney tissue to ammonia plus α –
ketoglutarate
d. The toxic ammonia generated from the amide nitrogen of amino acids is transported
through blood as arginine
2. The second amino group of urea is derived from;
a. Glutamate
b. Aspartate
c. Arginine
d. Free ammonia transported to the liver
3. The rate limiting step of the urea cycle is;
a. The first step which occurs in the mitochondria and requires the presence of Nacetylglutamate as a cofactor
b. The last step driven by arginase enzyme
c. The first two steps since it depends on the mitochondrial activity of the cell
d. The third step since it’s a step in the middle of the cycle and requires argininosuccinate
synthetase
4. A female neonate did well until approximately age 24 hours, when she became lethargic. A
sepsis workup proved negative. At 56 hours, she started showing focal seizure activity. The
plasma ammonia level was found to be 887 µmol/l (normal 5–35 µmol/l). Quantitative plasma
amino acid levels revealed a marked elevation of citrulline but not argininosuccinate. Which one
of the following enzymic activ...