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Carbohydrate and Nitrogen II

Module by: E. Pennington. E-mail the authorEdited By: E. Pennington

Summary: These are exercise test questions to help build your knowledge of carbohydrate and nitrogen lectures. This will help expand your knowledge on the topics to maximize learning at a deeper level, build confidence and help you succeed in the course.

Table 1
1. Which of the following statements about glucose transporters is TRUE?
A. The transporter for red blood cells is an insulin-sensitive transporter.
B. The transporter in spermatozoa function to transport fructose.
C. The transporter for muscle is a glucose sensor transporter.
D. The transporter for adipose tissue is a low affinity transporter.
E. The transporter for the liver is a high affinity transporter.
Table 2
2. Which of the following statements BEST states the clinical significance of glucose transporters in the brain?
A. The passage of glucose across the endothelial cells of the blood brain barrier is fast, thus maintaining a balance of supply and demand, especially during systemic hypoglycemia and seizures.
B. An ideal glucose level for normal neuronal function is 18-54 mg/dL and this prevents symptoms of light-headedness, dizziness or coma.
C. The levels of GLUT1 and GLUT3 remain constant from birth to adulthood and this facilitates neuronal maturation and synaptic activity in the brain.
D. Patients with Alzheimer's disease show reduced levels of GLUT1 and GLUT3 in regions that show deficits in cerebral glucose utilization.
E. Studies of glucose transporters in the brain do not offer any useful information for diseases like diabetes, hypoxia/ischemia, epilepsy and neurodegenerative disorders.
Table 3
3. Which of the following statements about muscle protein degradation is INCORRECT?
A. An ubiquitin-proteasome complex targets proteins that contains rich region of proline, glutamate, serine and threonine (PEST).
B. An active proteasome complex breaks down muscle proteins via a PA700 CAP with a PA28 subunit or a PA 28 subunit by itself.
C. Lysosomes contain cathepsins enzymes which break down muscle proteins and release amino acids into circulation.
D. Phagocytosis facilitates the intake and break down of muscle proteins in the inside of the lysosomes.
E. Calpains are cytosolic calcium regulated enzymes capable of breaking muscle proteins into amino acids.
Table 4
4. Which of the following CANNOT be broken down into amino acids by any of the enzymes that degrade proteins in the body?
A. Muscle
B. Plant Fiber
C. Hemoglobin
D. Digestive enzymes
E. Sloughed off cells of the intestines

Table 5
5. Which of the following statements about GLUT4 is INCORRECT?
A. GLUT4 is a glucose transporter predominantly found in adipose tissue and heart and skeletal muscle.
B. GLUT4 allows entrance of fructose inside the cells and expressed in cells with barrier functions.
C. Binding of insulin to a cell receptor activates the GLUT4 transporter to allow glucose inside the cells.
D. Insulin helps regulates the synthesis and activation of glycogen synthase for glycogen storage.
E. GLUT4 is inactive as an intracellular vesicle during periods of fasting and activated during the feeding state by insulin.
Table 6
6. Which of the following is NOT a common problem associated with excessive secretion of insulin?
A. Hypoglycemia
B. Depleted storage of glycogen
C. High storage of glycogen
D. Stimulation of synthesis of glycogen
E. Inhibition of glycogen degradation
Table 7
7. Which of the following statements about the fate of amino acids during fasting conditions is INCORRECT?
A. In the fasting state, amino acids from the digestion of dietary proteins travel to the liver for the synthesis of proteins.
B. In the intestines and lymphocytes, glutamine is converted to alanine and travels via circulation to the liver.
C. Amino acids from muscle protein are converted to alanine and glutamine and these are the main forms of transport in the blood.
D. The carbons of alanine are converted to glucose, CO2 and ketones bodies and the nitrogen is converted to urea in the liver.
E. In the kidneys, glutamine releases ammonia for the formation of salts with metabolic acids in the renal tubules.
Table 8
8. Which of the following intestinal enzymes is responsible for the activation of other intestinal zymogens under basic conditions?
A. Pepsin
B. Enteropeptidase
C. Trypsin
D. Chymotrypsin
E. Aminopeptidase
Table 9
9. Which of the following statements is MOST ACCURATE about the catalytic function of chymotrypsin and carboxypeptidase A in the digestion of proteins in the small intestine?
A. Cleaves peptide bonds with Arg and Lys side groups amino acids
B. Cleaves peptide bond in elastin and small side groups amino acids
C. Cleaves peptide bonds with hydrophobic side groups amino acids
D. Cleaves peptide bonds with basic side group amino acids
E. Cleave peptide bonds one amino acid at a time at the N-terminus ends of proteins
Table 10
10. Which of the following protein complexes works simultaneously in both the tricarboxylic acid and the electron transport chain during ATP synthesis?
A. Complex I
B. Complex II
C. CoQ
D. Complex III
E. Complex IV
Table 11
11. Which of the following statements is INCORRECT about oxidation-reductions reactions in the electron transport chain?
A. Initial reduction reactions involve accepting electrons from electrons donors of the tricarboxylic acid pathway.
B. The consumption of oxygen is a reduction reaction in which O2 accepts 4 electrons from complex IV and 4 protons from the proton wires.
C. Oxidation-reductions reactions happen sequentially by proteins accepting and donating electrons in the electron transport chain.
D. Oxidation-reduction reactions from electron transfer provide the energy necessary to pump protons out of the matrix.
E. Oxidation-reduction reactions are bidirectional making the electron transport chain reversible when ATP needs decreases.
Table 12
12. Which of the following statements MOST LIKELY shows the effects of decreased oxygen and cyanide poisoning?
A. Depletes iron stores in the bone marrow by impairing hemoglobin synthesis and causing severe iron lost in the tissues.
B. Maintains the amount of ATP nearly constant for metabolic needs of the tissues except for muscle.
C. Restores the electrochemical gradient to increase proton pumping and electrons to meet the high demands for ATP.
D. Causes cellular damage by directly affecting electron flow and proton pumping in the electron transport chain and ATP synthesis.
E. Gets incorporated into maternal mitochondrial DNA and is passed 100% of the time to the offspring.
Table 13
13. Which of the following statements is MOST ACCURATE about resting muscle?
A. High demands for ATP depletes the protons in the electrochemical gradient stimulating both the rate of ATP synthesis and the electron transport chain.
B. The buildup of electron carriers inhibits the enzymes of the tricarboxylic acid facilitating the export of intermediates of this pathway to other metabolic pathways.
C. Need for ATP is linked to increase concentrations of both adenosine diphosphate and pyrophosphate and the influx of protons into the matrix.
D. The amount remains nearly constant for all muscles in the body regardless whether muscle is contracting or resting.
E. O2 consumption speeds up electron flow, thus increasing the electron carriers from the tricarboxylic acid to supply more electrons for the electron transport chain.
Table 14
14. Which of the following pathways is responsible for the formation of cataracts as a result of high levels of galactose and glucose in blood and urine?
A. Glycolysis
B. Tricarboxylic acid
C. Polyol Pathway
D. Pentose Phosphate
E. Beta Oxidation
Table 15
15. Which of the following statements MOST LIKELY states the difference between classical and non-classical galactosemia?
A. Increased levels of galactose in urine.
B. Increased levels of galactose in blood.
C. Accumulation of galactose-1-phosphate in the tissues.
D. Formation of cataracts on the lenses of eyes via polyol pathway.
E. Aldose reductase converts blood galactose into galactitol.
Table 16
16. Which of the following amino acids, produced from intermediates of glycolysis, is used for the synthesis of both purine bases for nucleic acids and porphyrin for the hemoglobin molecule?
A. Glutamine
B. Glycine
C. Aspartate
D. Asparagine
E. Alanine
Table 17
17. Which of the following statements about lactose synthesis is INCORRECT?
A. One important site for lactose synthesis is the mammary gland right after childbirth under the influence of prolactin.
B. Lactose synthase is made up of two catalytic sites for the synthesis of lactose or glycoproteins based on hormonal stimuli.
C. Galactosyltransferase adds a galactose to a glucose molecule via β-1, 4 glycosidic bonds.
D. α-lactalbumin synthesizes glycoproteins when no prolactin is released and galactosyltransferase is inactive.
E. Alpha-lactalbumin increases the production of lactose in order to meet the dietary needs of a lactating infant every two hours.
Table 18
18. Which of the following statements about the urea cycle is INACCURATE?
A. The main carriers of nitrogen to the liver to enter the urea cycle are the amino acids alanine and glutamine.
B. The rate of ammonia (NH4+) formation speeds up the rate of the urea production to be sent to the kidneys for excretion.
C. A diet rich in high proteins with periods of prolong fasting in between meals stimulates the synthesis of all the enzymes of the urea cycle.
D. Increased synthesis of arginine facilitates the regeneration of ornithine and activates carbamoylphosphate synthetase I (CPSI).
E. Ornithine is an amino acid with an mRNA codon that is degraded into urea in the last step of the urea cycle.
Table 19
19. Which of the following molecules DOES NOTaccumulate in bloodas a result of a defect in any of the enzymes of the urea cycle?
A. Any of the intermediates of the urea cycle
B. Ammonia in the form of NH4+
C. Glutamine and alanine
D. All the intermediates of glycolysis
Table 20
20. Which of the following statements about jaundice is INCORRECT?
A. Neonatal jaundice is caused by the breakdown of fetal hemoglobin and an immature bilirubin conjugation system in the liver.
B. Unconjugated bilirubin is insoluble in plasma and accumulates in hydrophobic regions of the eyes and the skin.
C. Laboratory tests measure the levels of bilirubin in blood as indirect bilirubin, direct bilirubin and total bilirubin.
D. Yellow tinge of the skin and sclera of the eyes is seen when bilirubin blood levels are below 1 mg/dL.
E. In adults, it is caused by liver failure to transport, store or conjugate bilirubin, thus accumulating bilirubin in blood.

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