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Carbohydrate and Nitrogen II
E. Pennington
This work is produced by The Connexions Project and licensed under the Creative Commons Attribution License †
Abstract These are exercise test questions to help build your knowledge of carbohydrate and nitrogen lec- tures. This will help expand your knowledge on the topics to maximize learning at a deeper level, build con dence and help you succeed in the course.
- 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 a nity transporter. E. The transporter for the liver is a high a nity transporter.
Table 1
- Which of the following statements BEST states the clinical signi cance 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. continued on next page
∗Version 1.1: Dec 15, 2011 12:14 pm US/Central †http://creativecommons.org/licenses/by/3.0/
C. The levels of GLUT1 and GLUT3 remain constant from birth to adulthood and this facilitates neu- ronal maturation and synaptic activity in the brain.
D. Patients with Alzheimer's disease show reduced lev- els of GLUT1 and GLUT3 in regions that show de cits in cerebral glucose utilization.
E. Studies of glucose transporters in the brain do not oer any useful information for diseases like dia- betes, hypoxia/ischemia, epilepsy and neurodegen- erative disorders.
Table 2
- 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, ser- ine 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 3
- 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
continued on next page
B. In the intestines and lymphocytes, glutamine is con- verted 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 con- verted 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 7
- 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 8
- Which of the following statements is MOST ACCURATE about the catalytic function of chy- motrypsin 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 9
- 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 10
- Which of the following statements is INCORRECT about oxidation-reductions reactions in the electron transport chain?
A. Initial reduction reactions involve accepting elec- trons 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 trans- fer 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 11
- Which of the following statements MOST LIKELY shows the eects of decreased oxygen and cyanide poisoning?
A. Depletes iron stores in the bone marrow by impair- ing hemoglobin synthesis and causing severe iron lost in the tissues. continued on next page
C. Polyol Pathway
D. Pentose Phosphate
E. Beta Oxidation
Table 14
- Which of the following statements MOST LIKELY states the dierence 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 tis- sues.
D. Formation of cataracts on the lenses of eyes via polyol pathway.
E. Aldose reductase converts blood galactose into galactitol.
Table 15
- 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 16
- Which of the following statements about lactose synthesis is INCORRECT?
A. One important site for lactose synthesis is the mam- mary gland right after childbirth under the in u- ence of prolactin.
B. Lactose synthase is made up of two catalytic sites for the synthesis of lactose or glycoproteins based on hormonal stimuli. continued on next page
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 in- active.
E. Alpha-lactalbumin increases the production of lac- tose in order to meet the dietary needs of a lactating infant every two hours.
Table 17
- 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 glu- tamine.
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 regen- eration of ornithine and activates carbamoylphos- phate 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 18
- 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 19
