Dental Biochemistry
Final Exam
December 11, 2012
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2. Mark only one answer for each question. Answer every question even if you think the question is flawed or you have no idea of the answer.
3. The exam has 100 multiple-choice questions. You have 3 hour 50 minutes to complete the exam.
4. You should keep your copy of the exam. The answers will be posted on the course web page ( this afternoon. The exam scores will be recorded in blackboard in one to two days. An announcement will be posted at when blackboard has the grades.
5. Challenges should be sent to your class liaison by Friday.
1. Which of the following is an essential amino acids in adults?
a. glutamine
b. serine
c. tryptophan
d. tyrosine
e. arginine
2. Which one of the following DOES NOT correctly match a compound with its amino acid precursor?
a. nitric oxide, arginine
b. norepinephrine, tryptophan
c. dopamine, tyrosine
d. homocysteine, methionine
e. serotonin, tryptophan
3. In which one of the following tetrahydrofolates is the one carbon unit (in bold) at the same oxidation level as in the methyl group in S-adenosyl methionine?
A / B / C / D / E4. The role of sodium urate crystals in gout is to ____.
a. act as an inflammatory trigger
b. generate neurological malfunctions
c. inhibit replication of lymphocytes
d. physically abrade the joint cartilage
e. cause an autoimmune reaction
5. The enzyme ribonucleotide reductase converts ribonucleotides to deoxyribonucleotides and is inhibited by high concentrations of any deoxynucleoside triphosphate. The role of this enzyme in adenosine deaminase (ADA) deficiency is that ____.
a. drugs to inhibit this enzyme are the first line of treatment for this disease
b. it is the first enzyme successfully replaced by gene therapy
c. it becomes inappropriately up regulated as a result of the ADA defect
d. it becomes inhibited by salvaged dATP in lymphocytes causing them to fail to replicate
e. a mutation in the gene for ribonucleotide reductase underlies the disorder
6. Lesch-Nyhan syndrome is only found in males because ___.
a. only males drink enough caffeine to manifest symptoms
b. only males conduct purine salvage
c. the female sex hormone, estrogen, counteracts the symptoms
d. males, on average, have higher serum sodium urate levels
e. the affected gene is X-linked
7. Which one of the following statements about unsaturated fatty acids is FALSE?
a. They form a higher portion of vegetable oils than of animal fat.
b. They have a higher melting temperature than saturated fatty acids, and therefore give food a more solid consistency.
c. Two of them, linoleic acid (cis,cis-9,12-octadecadienoic acid) and alpha linolenic acid (cis,cis,cis-9,12,15-octadecatrienoic acid), will satisfy an essential requirement in the human diet.
d. The precursors for the synthesis of eicosanoids are unsaturated fatty acids.
e. In membranes, unsaturated fatty acids help provide for membrane fluidity.
8. Which one of the following has both a structure based on cholesterol and a total of 18 carbons?
a. estrogen (a sex hormone)
b. bile salts
c. prostaglandins
d. mineralocorticoids and glucocorticoids
e. vitamin D
9. Deficiency of which one of the following fat soluble vitamins leads to up to 500,000 cases of blindness a year?
a. vitamin A
b. vitamin D
c. vitamin E
d. vitamin K
e. all of the above; they are all required for vision
10. Which one of the following statements is a plausible reason why inhibitors of cyclooxygenase are of no help in treating asthma?
a. There are no inhibitors of cyclooxygenase.
b. Asthma is associated with leukotrienes, which are eicosanoids produced by lipoxygenase, not by cyclooxygenase.
c. Cyclooxygenase only makes prostaglandins involved in pain reception, not in inflammatory reactions.
d. Cyclooxygenase is involved in fatty acid synthesis, not in anything to do with inflammation.
e. Humans don't make cyclooxygenase.
11. Lipoprotein lipase removes fatty acids from triacylglycerol in chylomicrons. Which one of the following statements about this interaction is FALSE?
a. This interaction occurs in capillary beds.
b. The released fatty acid may be taken up by an adipocyte and resynthesized to triacylglycerol.
c. The source of the chylomicron triacylglycerol was dietary fat, hence this is part of the process of utilizing or storing dietary fats.
d. The released glycerol passes through the circulation and may be taken up by the liver to make glucose.
e. The released fatty acids pass through the circulation until taken up by the liver.
12. Which one of the following statements about mobilization of fat from adipocytes is FALSE?
a. Insulin up-regulates the release of fatty acids from adipocytes.
b. Mobilization of stored fat starts with activation of lipases (adipocyte triacylglycerol lipase and hormone sensitive lipase).
c. Mobilization is ultimately controlled by the sympathetic nervous system through secretion of epinephrine.
d. The process is controlled by the cAMP and protein kinase A (PKA) signalling pathway.
e. Released fatty acids are transported by serum albumin.
13. Which one of the following statements about beta oxidation of fatty acids in muscles is FALSE?
a. This is the primary source of energy for driving muscular activity when resting or at a low exertion level.
b. Insulin causes diversion of imported fatty acids away from beta oxidation and into local storage, leading to increased utilization of glucose.
c. A key step in regulating beta oxidation is by inhibition by malonyl CoA ofthe enzyme that imports fatty acids into mitochondria.
d. Beta oxidation produces acetyl CoA which goes into the TCA cycle to make ATP as well as directly producing NADH and FADH2.
e. Beta oxidation generates a total of 56 ATP molecules from a single molecule of C18:0 fatty acid.
14. Ketosis is a process that ____.
a. operates as an alternative to relying on fat stores for energy utilization
b. reduces destruction of protein during prolonged periods of dietary carbohydrate shortage
c. makes glucose from acetyl-CoA
d. only occurs in diabetics
e. leads to cholesterol depletion
15. A 25 year old male has a basal metabolic rate of ~ 1800 calories per day, eats 2200 calories of food on a particular day, burns off about 550 calories in a vigorous basketball game, and weighs in as four pounds lighter immediately after the game. What's his approximate net loss in fat over this day?
a. -1 pound (meaning he has gotten fatter)
b. 0
c. 0.1 pound
d. 1 pound
e. 4 pounds
16. A person eats adequate total calories about half in carbohydrates and half in fat.He consumes adequate amounts of essential fatty acids, vitamins, and twice the total protein requirement per day of 1.5g per kilogram body weight. He is not diabetic. He still shows symptoms of protein deficiency. Which one of the following could be the cause?
a. At half fat and half carbohydrate, he will be in ketosis.
b. This is a typical outcome for an obese person in a prediabetic state.
c. This diet doesn't have the required level of cholesterol.
d. The person is very nervous, causing high epinephrine levels to impede utilization of fat for his energy needs.
e. Although the total protein may be adequate, there may be a shortage in a particular essential amino acid.
17. A person with a typical daily meal and sleep cycle is experiencing a dream at 2:00 am. The brain is being powered at this time by ____.
a. liver glycogen
b. muscle glycogen
c. adipocyte fat
d. ketone bodies
e. chylomicrons
18. The organ that normally accounts for about 1/2 the daily glucose consumption and increases reliance on ketone bodies 2-3 days into starvation is ____.
a. liver
b. brain
c. muscle
d. fat depot
e. kidney
19. In juvenile diabetes (a congenital inability to make insulin) failure to treat with insulin would lead to which one of the following series of events.
a. high blood sugar, damage to muscles, insulin resistance, obesity
b. low blood sugar, profuse sweating, loss of consciousness
c. rampant ketone body production, drop in blood pH, diabetic coma, death
d. normal blood sugar maintained by gluconeogenesis, prolonged survival with progressive muscle loss
e. inflammation, destruction of joint cartilage
20. Which one of the following is NOT characteristic of type II diabetes?
a. typically adult onset, but now being seen in children
b. strongly linked to obesity
c. preceded by a prediabetic state featuring insulin resistance, high insulin, but normal blood sugar
d. involvement of an autoimmune attack against pancreatic beta cells
e. eventual loss of insulin secretion
21. The component of biological membranes that gives them their characteristic bilayer structure is ____.
a. cholesterol
b. proteins
c. cholesterol ester
d. phosphoglycerides
e. sphingolipids
22. A membrane component allows glucose to pass, but only if accompanied by a Na+ ion. This is an example of ____.
a. active transport
b. passive transport
c. antiport
d. membrane signaling
e. living cells violating the laws of thermodynamics
23. Which one of the following INCORRECTLY matches a lipoprotein with one of its functions?
a. LDL; deliver cholesterol by endocytosis
b. HDL; retrieve excess cholesterol from cells
c. chylomicrons; deliver dietary fatty acids to adipose cells
d. VLDL; deliver dietary cholesterol to the liver
e. HDL; exchange cholesterol with other lipoproteins
24. Penicillin acts as a substrate analogue of ____.
a. N-acetylmuramic acid, N-acetylglucosamine (NAM-NAG)
b. pentaglycine
c. D-Ala, D-Ala dipeptide
d. beta-lactam
e. finished cell wall
25. Beta lactamase renders a bacterium penicillin-resistant by ____.
a. cleaving the cell wall
b. cleaving a peptide bond in a beta lactam ring
c. cleaving a D-ala, D-ala dipeptide
d. pumping penicillin out of the cell
e. joining pentaglycine to the oligopeptide of peptidyl N-acetylmuramic acid (NAM)
26. Which one of the following is NOT associated with R factor-mediated antibiotic resistance?
a. It causes hospital-acquired infections to be more dangerous than the average infection.
b. Switching antibiotics for a patient with an R factor-mediated antibiotic resistant infection tends to fail.
c. Prior treatment with one antibiotic may cause failure of treatment with a different antibiotic.
d. R factors are associated with the increase in penicillin-resistant bacterial infections.
e. R factors help patients with viral infections to benefit from antibiotic treatment.
27. Prostaglandin E1 is a (an) ______hormone.
a. amino acid-derived
b. polypeptide
c. steroid
d. eicosanoid
28. Which one of the following is a basic taste that is provided by denatonium cation?
a. sweet
b. sour
c. salty
d. umami
e. bitter
29. Which one of the following is a characteristic that some hormone activity pathways have in common with some taste pathways? (Consider only information presented in class)
a. heterotrimeric G protein
b. binding of an insulin-like receptor
c. regulation of the rate of transcription
d. stimulation of phosphorylation of an ion channel
e. direct blocking of an ion channel
30. When the thyroid gland is abnormal and over-stimulation of the thyroid gland is the only abnormality (in Graves disease, for example), the finding is that thyroxine is ______.
a. low and thyroid stimulating hormone (TSH) is high
b. high and TSH is high
c. high and TSH is low
d. low and TSH is low
e. low and insulin is high
31. Which one of the following hormones is both water soluble and endocrine?
a. prostaglandin E1
b. thromboxane A2
c. thyroxin
d. norepinephrine
e. cortisol
32. Which one of the following hormones is tropic (signals an endocrine gland to release another hormone)?
a. insulin
b. ACTH
c. epinephrine
d. norepinephrine
e. thyroxine
33. You are reading an article about the effects of parathyroid hormone. The article mentions a membrane-bound receptor that does not self-phosphorylate and does not enter the cytoplasm. Which one of the following is implied, based only what was covered in class?
a. Parathyroid hormone is hydrophobic and binds to a carrier protein in theserum.
b. The receptor for parathyroid hormone must be insulin-like and not coupledto a heterotrimeric G protein.
c. Parathyroid hormone binds to a receptor that is coupled to a heterotrimeric Gprotein.
d. Parathyroid hormone works by altering transcription.
e. Parathyroid hormone is paracrine.
34. In class, we discussed correlation of tastant with taste bud and the making of thiscorrelation by fluorescence microscopy. In this case, increase in fluorescence wasstimulated by Ca++ that was releasedafter cleavage of ______.
a. cGMP
b. cAMP
c. adenylate cyclase
d. PIP2
e. a heterotrimeric G protein
35. Which one of the following is secreted by a gland that is located on the top of a kidney?
a. prostaglandin E1
b. ACTH
c. cortisol
d. parathyroid hormone
e. thyroxine
36. Which of the following is a CORRECT statement regarding long bones and flat bones?
a. The two types of bone are formed by the same mechanism.
b. Flat bones maintain the rigid structure of the heart muscle.
c. Both flat and long bones provide an essential reservoir of calcium.
d. Long bones are unique in that they are not remodeled after initial formation.
e. The distinguishing difference between flat and long bones is the content of enamelysin.
37. Which one of the following is an INCORRECT statement about RGD-containing proteins?
a. The only two RGD-containing proteins are fibronectin and vitronectin.
b. The RGD motif provides a site of attachment for bone cells.
c. Interactions of RGD-containing proteins and osteoclast membrane receptors are required to form a resorption compartment.
d. Bone sialoprotein is an RGD-containing protein which also has a glutamic acid-rich region.
e. The RGD-containing protein osteopontin has a calcium and hydroxyapatite binding properties.
38. Which one of the following is a CORRECT statement about the post-translational modification of Gla-proteins in bone?
a. The post-translational modification occurs at cysteine residues in Gla-proteins.
b. The post-translational modification of Gla-proteins is vitamin B-dependent.
c. The post-translational modification of Gla-proteins enhances calcium binding.
d. The post-translational modification increases the number of positive charges on Gla-proteins.
e. The post-translational modification of osteocalcin occurs equally in bone and nerve cells.
39. Which one of the following is a CORRECT statement about the cells of bone?
a. Bone surfaces are covered throughout by a continuous layer of osteoblasts.
b. Osteocytes are distinguished from other bone cells by their multinucleated appearance.
c. All bone cells maintain direct contact with and are nourished by small blood vessels.
d. Osteocytes are osteoclasts that become embedded in bone during bone formation.
e. Osteoclasts are found in clusters of 4-6 cells in resorption lacunae.
40. Which one of the following is a CORRECT statement about the origin of osteoclasts and osteoblasts?
a. Osteoblasts are derived from hematoprogenitor cells.
b. Osteoclasts are derived from immature osteoblasts.
c. Osteoblasts are derived from neural crest cells.
d. Osteoclasts are derived from lining cells.
e. Osteoblasts are derived from local mesenchymal stem cells.
41. Which of the following statements CORRECTLY characterizes osteoblasts?
a. Osteoblasts express amelogenin.
b. Osteoblasts express acid phosphatase.
c. Osteoblasts have receptors for vitamin D3.
d. Osteoblasts have a life span of about 3 weeks.
e. Osteoblasts secrete PTH.
42. Which one of following is a CORRECT statement regarding the functional and structural organization of bone?
a. Canaliculi in bone are formed in response to a diet deficient in vitamin C.
b. Haversian systems are functional units that contain a central canal with blood supply.
c. Osteoblasts possess long extensions that are not present on osteoclasts.
d. Osteocytes undergo rapid apoptosis as they are embedded in bone.
e. Each Haversian system is lined on all sides by a layer of lining cells.
43. During bone remodeling, TGF-beta is released. This is important because ______.
a. TGF-beta stimulates osteoclast proliferation
b. TGF-beta increases RANKL expression and thereby osteoclast differentiation
c. TGF-beta stimulates osteoblast proliferation and protein synthesis
d. TGF-beta has no detectable effects on osteoblasts
e. TGF-beta effects enhance bone degradation
44. Which one of the following events does NOT pertain to degradation of the organic matrix during bone resorption?
a. Lysosomal enzymes hydrolyze proteins.
b. MMPs and cathepsins cleave collagens.
c. Protein fragments are internalized in secondary lysosomes.
d. Short relapses of the sealing zone release cleavage products from the osteoclasts.
e. Reduced pH completely dissolves type I collagen fibers.
45. Which of the following statements is NOT correct about parathyroid hormone (PTH)?
a. PTH production and release occur in response to signaling via calcium receptors.
b. PTH acts on cells via an estrogen receptor.
c. PTH has effects on both kidney cells and bone cells.
d. PTH release is increased in response to hypocalcemia.
e. PTH producing cells may increase in number during longstanding hypocalcemia.
46. Which of the following statements (I-V) regarding the synthesis and processing of vitamin D3areCORRECT?
I. Vitamin D3 is formed in the skin
II. Vitamin D3 is activated by two hydroxylation steps
III. 1,25-dihydroxy-vitamin D3 produced in the kidney is active
IV. 25-hydroxy-vitamin D3 produced in the liver is active
V. Vitamin D3 is activated by one hydroxylation step
a. I and IV
b. I and V
c. II and III
d. III and IV
e. IV and V
47. Which of the following signs may be observed as a result of HYPO-parathyroidism with respect to tooth development?
a. hyperplasia of the enamel
b. delayed tooth development
c. formation of extra teeth
d. increase in tooth root length
e. No changes are detectable.
48. Which of the following properties is NOT shared by 1) ameloblasts during the maturation phase of enamel formation and 2) osteoclasts during bone resorption in long bones?
a. high levels of enzyme-rich lysosomes
b. endocytosis of proteolytic fragments
c. carbonic anhydrase mediated regulation of pH
d. efficient cleavage of amelogenins
e. expression and secretion of MMPs and cathepsin B
49. It is a CORRECT statement regarding dentin mineralization that ______.
a. mineralization precedes formation of an organic matrix
b. mineralized crystals are deposited along both fibrillar amelogenins and collagens
c. all tubules are obliterated by hydroxyapatite as the odontoblast processes recede
d. odontoblasts secrete vesicles that are rich in Ca2+ and PO43-
e. the complete width of the predentin is formed prior to initiation of mineralization
50. Which of the following observations has been made regarding amelogenin during enamel formation?
a. Amelogenin is a minor protein component of developing enamel
b. Amelogenin is present in several molecular forms due to alternative splicing
c. Amelogenin is resistant to cleavage by all MMPs
d. Amelogenin increases in amount during the maturation phase
e. Amelogenin fragments have no biological activities
Comprehensive Section
51. Which of the following are NOT found in a prokaryote?