Test #1: Vitamin D and Calcium

All 40 questions!!

1. The new RDA for Vitamin D that was set in 2011:

Question 1 options:

	(a) Supported a much higher level of Vitamin D intake than before, because of highly publicized health claims for excessive intakes
	(b) Assumed that most people get enough Vitamin D from sunlight and don't need a dietary source
	(c) Took into account that most people over 70 years of age have undiagnosed parathyroid gland tumors that could decrease Vitamin D requirements
	(d) Was based on an exhaustive review of the scientific literature that took into account new quantitative data since 1997
	(e) Concluded that people don't need dietary Vitamin D if they get enough calcium

d

 

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2. The RDA and UL for dietary Vitamin D for males and females ages 9-70 years is:

Question 2 options:

	(a) RDA: 6 IU (0.15 mg) and UL: 600 IU (15 mg)
	(b) RDA: 60 IU (1.5 mg) and UL: 40,000 IU (1000 mg)
	(c) RDA: 600 IU (15 mg) and UL: 40,000 IU (1000 mg)
	(d) RDA: 600 IU (15 mg) and UL: 4000 IU (100 ug)
	(e) RDA: 6000 IU (150 mg) and UL: 10,000 IU (250 mg)

d

3. Ergocalciferol (Vitamin D2):

Question 3 options:

	(a) Is considered to have similar bioactivity to Vitamin D3 in regulating calcium and preventing rickets
	(b) Is the plant form of Vitamin D
	(c) Is active without metabolism, unlike Vitamin D3 that requires activation by hydroxylations in the liver and kidneys
	(d) a, b & c
	(e) a & b only

e

4. The RDA for Vitamin D assumes that calcium intake is adequate because:

Question 4 options:

	(a) The RDAs for Vitamin D are based on requirements for bone health, which requires adequate calcium
	(b) Insufficient calcium changes the metabolism of Vitamin D
	(c) No amount of Vitamin D can compensate for inadequate calcium
	(d) a, b & c
	(e) a & b only

d

5. Fortified dietary sources of Vitamin D include:

Question 5 options:

	(a) milk and fish
	(b) milk and margarine
	(c) milk and liver
	(d) liver and fish
	(e) margarine and liver

b

6. Choose the statement about the intestinal absorption of Vitamin D that is FALSE: 

Question 6 options:

	(a) Vitamin D is transported into enterocytes by D9K
	(b) Efficient Vitamin D absorption requires the formation of micelles
	(c) About 50% of Vitamin D is typically absorbed
	(d) Enterocytes secrete Vitamin D into the lymph in chylomicrons
	(e) Chylomicrons in the blood can transfer Vitamin D to circulating Vitamin D Binding Protein

a

7. Vitamin D synthesis in the skin does not produce toxic blood levels of Vitamin D since:

Question 7 options:

	(a) Excess levels of the unstable intermediate are converted to Lumisterol and Tachysterol by continued UV exposure, preventing the formation of excessive levels of cholecalciferol
	(b) Tachysterol and Lumisterol have a low affinity for the Vitamin D binding protein, and therefore remain in the skin
	(c) Once Vitamin D binding protein is saturated, Vitamin D remains in the skin and doesn't enter the blood
	(d) All of the above
	(e) a and b only

d

8. UVB rays in sunlight help form Vitamin D in the skin by: 

Question 8 options:

	(a) Converting cholesterol to 7-dehydrocholesterol
	(b) Converting 7-dehydrocholesterol to an unstable intermediate
	(c) Converting cholecalciferol (Vitamin D3) to 7-dehydrocholesterol
	(d) Converting cholecalciferol (Vitamin D3) to tachysterol
	(e) Increasing sebum production

b

9. Inactive Vitamin D (cholecalciferol) is enzymatically activated to 25(OH) Vitamin D (calcidiol) and then 1,25(OH)₂ Vitamin D (calcitriol) by:

Question 9 options:

	(a) Nothing. Vitamin D from dietary sources or sunlight is already active
	(b) A hydroxylation reaction first in the liver, followed by a hydroxylation reaction in the kidneys
	(c) A hydroxylation reaction first in the kidneys, followed by a hydroxylation reaction in the liver
	(d) Binding to the nuclear Vitamin D receptor in cells
	(e) UV irradiation in the skin

b

10. The enzyme that forms fully active 1,25(OH)₂ Vitamin D (calcitriol), the substrate that it uses, and the tissue where it is found at highest levels, respectively, are: 

Question 10 options:

	(a) 1-a hydroxylase, cholecalciferol (Vitamin D), skin
	(b) 24-hydroxylase, cholecalciferol (Vitamin D), kidney
	(c) 1-a hydroxylase, 25(OH) Vitamin D (calcidiol), kidney
	(d) 24-hydroxylase, cholecalciferol (Vitamin D), liver
	(e) 1-a hydroxylase, 25(OH) Vitamin D (calcidiol), liver

c

11. Choose the statement about Vitamin D that is FALSE:

Question 11 options:

	(a) 1,25(OH)2 Vitamin D (calcitriol) is a ligand for the nuclear vitamin D receptor
	(b) 1,25(OH)2 Vitamin D (calcitriol) can activate the MARRS receptor to increase calcium transport into cells
	(c) The circulating half-life of 25(OH) Vitamin D is only a few minutes, but the circulating half-life of 1,25(OH)2Vitamin D is a few weeks
	(d) Although kidneys are the major site where 25(OH) Vitamin D is hydroxylated to 1,25(OH)2 Vitamin D, many cells express at least a little 1-a hydroxylase
	(e) Vitamin D3 (cholecalciferol) is hydroxylated to 25(OH) Vitamin D3 primarily in the liver

c

12. 1,25(OH)₂ Vitamin D (aka calcitriol) functions genomically to help increase the level of blood calcium by:

Question 12 options:

	(a) Inducing Calcium ATPase (Ca-ATPase) expression in enterocytes
	(b) Suppressing 1-a hydroxylase expression in the kidneys
	(c) Inducing 24-hydroxylase expression in the kidneys
	(d) Suppressing parathyroid hormone expression in the parathyroid gland
	(e) Suppressing TRPV6 expression in enterocytes

a

13. 1,25(OH)₂ Vitamin D (aka calcitriol) functions genomically to increase renal reabsorption of calcium by: 

Question 13 options:

	(a) Inducing transcription of TRPV5 but not TRPV6
	(b) Inducing transcription of D9K
	(c) Inducing transcription of 1-alpha-hydroxylase
	(d) Inducing transcription of D28K
	(e) Inducing phosphorylation of TRPV5

d

14. The Membrane-associated, rapid response steroid-binding (MARRS) receptor:

Question 14 options:

	(a) Is a nuclear transcription factor that is activated by binding 1,25(OH)2 Vitamin D (calcitriol)
	(b) Acts on the order of hours to days to increase the gene expression of TRPV6
	(c) Is a G-protein coupled receptor that acts within minutes to open voltage-dependent calcium channels (VDCC) in enterocytes
	(d) Has been shown to be unnecessary for calcium absorption in the gut, since mice lacking MARRS have no change in calcium uptake from the diet
	(e) Is a nuclear transcription factor that increases expression of intestinal calbindin D9K

c

15. Which of the following statement(s) about Vitamin D and bone are true:

Question 15 options:

	(a) 1,25(OH)2 Vitamin D (aka calcitriol) activates osteoblasts, which secrete alkaline phosphatase and HCl to resorb bone
	(b) 1,25(OH)2 Vitamin D (aka calcitriol) activates osteoblasts to secrete RANKL, which activates osteoclasts, causing them to secrete alkaline phosphatase and HCl to resorb bone
	(c) Adequate intakes of Vitamin D protect bones indirectly, by ensuring optimal dietary calcium absorption
	(d) a & c
	(e) b & c

e

16. Vitamin D activation is primarily controlled by changes in blood calcium levels because: 

Question 16 options:

	(a) Calcium binds to 1-a hydroxylase, causing a conformational change that activates the enzyme
	(b) A rise in blood calcium induces calcitonin, which increases the transcription of 1-a hydroxylase
	(c) A fall in blood calcium 'takes the brakes off' of the 1-a hydroxylase enzyme, allowing it to hydroxylate 25(OH) Vitamin D
	(d) A fall in blood calcium 'takes the brakes off' of the Calcium Sensing Receptor (CASR), allowing parathyroid hormone secretion to occur, which induces kidney 1-a hydroxylase mRNA expression
	(e) None of the above

d

17. 1,25(OH)₂ Vitamin D (calcitriol) functions to limit its own activity and restore blood calcium homeostasis by: 

Question 17 options:

	(a) Inhibiting parathyroid hormone synthesis
	(b) Raising blood calcium levels, which activates the calcium-sensing receptor (CaSR) to limit parathyroid hormone secretion
	(c) Inhibiting kidney 1-a hydroxylase transcription
	(d) Inducing 24-hydroxylase to divert 25(OH) Vitamin D to the synthesis of 24,25(OH)2 Vitamin D
	(e) All of the above

e

18. Vitamin D deficiency:

Question 18 options:

	(a) Can impair myogenesis because myoblasts express 1-a hydroxylase during muscle fibre formation to synthesize 1,25(OH)2 Vitamin D (calcitriol) needed for local use within the tissue
	(b) Decreases muscle strength by reducing myocyte signaling through the nuclear Vitamin D Receptor, but has no effect on Ca-ATPase pumps, which aren't expressed in myocytes
	(c) Affects muscle strength but not formation because myoblasts since they don't express nuclear Vitamin D Receptors
	(d) Causes improved muscle strength since increased parathyroid hormone secretion induces myoblasts to differentiate to form new muscle cells
	(e) Increases synthesis of calcium ATPase pumps and voltage-sensitive calcium channels in myocytes

a

19. Vitamin D:

Question 19 options:

	(a) Toxicity (i.e. blood levels >375 nM or 150 ng/ml) can cause symptoms such as excessive bone loss
	(b) Is primarily excreted in the urine since Vitamin D is a water-soluble vitamin
	(c) Toxicity (i.e. blood levels >375 nM or 150 ng/ml) can cause symptoms such as nausea, weakness and renal dysfunction
	(d) a & b
	(e) a & c

e

20. Elderly individuals (>70 years) have an increased requirement for Vitamin D because:

Question 20 options:

	(a) They have an age-related reduction in the ability of parathyroid hormone (PTH) to induce renal 1α-hydroxylase
	(b) They have increased induction of 24-hydroxylase in the kidney, which produces a less active form of Vitamin D that is more easily degraded
	(c) They have elevated parathyroid hormone (PTH), and need more Vitamin D to suppress synthesis of this hormone
	(d) They spend more time in the sun since they are retired and can move to sunny places in the winter
	(e) They have increased production of 7-dehydrocholesterol in the skin with aging

a

21. Skin melanin concentration:

Question 21 options:

	(a) Does not affect the risk of Vitamin D deficiency
	(b) Is correlated with lower circulating 25(OH)Vitamin D concentrations
	(c) Should be considered in Public Health efforts aimed at ensuring Vitamin D sufficiency in Canada
	(d) a & b
	(e) b & c

e

22. Which statement or statements about body calcium are correct:

Question 22 options:

	(a) Approximately 25% of total body calcium is located in the bones and teeth
	(b) Approximately 1% of total body calcium is found in the intracellular and extracellular fluids, muscle, and blood
	(c) There is 10,000 times more calcium inside cells than in the extracellular space outside cells
	(d) a & b
	(e) a & c

b

23. Which of the following statements about the calcium DRIs is TRUE:

Question 23 options:

	(a) The RDA during lactation is not increased because dietary calcium absorption and urinary calcium reabsorption are higher during lactation
	(b) The RDA for calcium is higher in males aged 51-70 years than in males aged 19-50 years
	(c) The RDA during pregnancy is not increased because dietary calcium absorption and urinary reabsorption are higher during pregnancy
	(d) The UL for calcium is higher in female children than male children
	(e) After age 70 the RDA and the UL both increase for males

c

24. Consuming calcium together with food that has a high saturated fat content:

Question 24 options:

	(a) Can cause the formation of fatty soaps that are well absorbed and increase calcium bioavailability
	(b) Can cause the formation of fatty soaps that are poorly absorbed and decrease calcium bioavailability
	(c) Can cause the formation of fatty soaps, but this does not affect calcium bioavailability
	(d) Causes calcium to precipitate with oxalate in the gastrointestinal tract
	(e) Increases the risk of kidney stones

b

25. Dietary calcium is:

Question 25 options:

	(a) More bioavailable from dried beans than from dairy products
	(b) Higher in milk, but more bioavailable from spinach
	(c) Only found in animal products
	(d) Less bioavailable from supplements than from plant foods
	(e) None of the above

e

26. Calcium is actively absorbed from the diet by:

Question 26 options:

	(a) Transport from the intestinal lumen into the enterocyte through TRPV6, transport through the enterocyte by D9K, and transport from the enterocyte into the blood via a Calcium-ATPase pump
	(b) Paracellular transport in-between cells via TRPV6 and binding to D9K
	(c) Paracellular transport between cells via Claudin 2
	(d) Binding to renal calbindin (D28K)
	(e) All of the above

a

27. People with a high intake of dietary plant matter (e.g. vegans) can have adaptations that increase dietary calcium absorption including:

Question 27 options:

	(a) Increased reaction of calcium with phytate to form insoluble compounds that are highly absorbed
	(b) Increased production of short chain fatty acids that improve claudin2-mediated paracellular calcium absorption in the colon
	(c) Increased production of short chain fatty acids that decrease the number of colonocytes and reduce the colon absorptive surface
	(d) Increased production of short chain fatty acids that increase the pH of the colon to make calcium less soluble
	(e) All of the above

b

28. A rise in free (ionized) blood calcium concentration to a level above normal:

Question 28 options:

	(a) Activates the calcium-sensing receptor (CaSR) on cells of the parathyroid gland, which causes increased parathyroid hormone (PTH) secretion
	(b) Activates the calcium-sensing receptor (CaSR) on cells of the parathyroid gland, which inhibits parathyroid hormone (PTH) secretion
	(c) Inhibits the calcium-sensing receptor (CaSR) on cells of the parathyroid gland, which inhibits parathyroid hormone (PTH) secretion
	(d) Inhibits the calcium-sensing receptor (CaSR) on cells of the parathyroid gland, which allows increased parathyroid hormone (PTH) secretion
	(e) None of the above

b

29. A fall in free (ionized) blood calcium concentration to a level below normal:

Question 29 options:

	(a) Will trigger secretion of parathyroid hormone (PTH) that induces 1-a hydroxylase to increase blood 1,25(OH)2Vitamin D levels
	(b) Will result in induction of intestinal TRPV6, D9K, Ca-ATPase and claudin 2 by 1,25(OH)2 VitD to increase absorption of calcium
	(c) Will result in induction of renal calbindin (D28K) by both parathyroid hormone (PTH) and 1,25(OH)2 VitD to conserve calcium
	(d) All of the above
	(e) None of the above

d

30. Parathyroid hormone (PTH) acts directly to:

Question 30 options:

	(a) Lower blood calcium by promoting the deposition of calcium in bone, and by increasing the absorption of calcium from the intestines
	(b) Raise blood calcium by increasing reabsorption of calcium from the kidneys as well as absorption from the intestines, without having any effects on bone
	(c) Raise blood calcium by increasing resorption of calcium from bone and increasing reabsorption of calcium from the kidneys, as well as absorption of dietary calcium from the intestines
	(d) Lower blood calcium by promoting formation of bone and by decreasing reabsorption of calcium from the kidneys as well as absorption from the intestines
	(e) Raise blood calcium by increasing resorption of calcium from bone and increasing reabsorption of calcium by the kidneys, without acting directly on the intestines

e

31. Functions of calcium include all of the following except:

Question 31 options:

	(a) Blocking coagulation by preventing the synthesis of fibrin
	(b) Aiding in the mobilization of acetylcholine vesicles to the synapse to cause neurotransmission
	(c) Providing structural integrity for bones and teeth
	(d) Inducing a conformational change in troponin C allowing myosin to interact with actin to cause skeletal muscle contraction
	(e) Activating cellular enzymes to generate secondary messengers and signal transduction

a

32. The hormone calcitonin:

Question 32 options:

	(a) Rapidly inhibits osteoclast motility (within 1 minute)
	(b) Impairs differentiation of pre-osteoclasts to mature osteoclasts to cause a lasting effect
	(c) Is produced in the parafollicular cells of the thyroid gland
	(d) Reduces blood calcium input from bone
	(e) All of the above

e

33. Rickets:

Question 33 options:

	(a) Is a disease that can only occur after the bones have stopped growing
	(b) Is considered a type of osteomalacia where existing bone mineral is reabsorbed
	(c) Is ruled out when blood 1,25(OH)2 Vitamin D (calcitriol) levels are high, since this hormone increases bone mineralization
	(d) Is characterized by hypocalcemia
	(e) Is characterized by a reduction in both bone mineral and the protein (osteoid) matrix of bone

b

34. Rickets:

Question 34 options:

	(a) Is most commonly associated with dietary calcium deficiency but sufficient vitamin D intakes
	(b) Is treated with calcium only, because elevated parathyroid hormone levels will ensure dietary calcium is absorbed, regardless of vitamin D status
	(c) Is most commonly caused when vitamin D deficiency impairs calcium absorption, preventing adequate mineralization at the epiphyseal plate
	(d) Is associated with increased sun exposure
	(e) None of the above

c

35. High intakes of calcium taken with meals:

Question 35 options:

	(a) May decrease the risk of kidney stones by binding oxalate in the gut to prevent its absorption
	(b) May increase the risk of kidney stones since calcium will be absorbed in a complex bound to dietary oxalate
	(c) May increase the bioavailability of other micronutrients such as Vitamin D
	(d) May cause improved gastrointestinal motility and create a feeling of euphoria
	(e) All of the above

a

36. The RDA for Calcium is increased in post-menopausal women because:

Question 36 options:

	(a) Post-menopausal bone loss can be completely prevented if women get enough dietary calcium
	(b) Calcium absorption decreases after menopause because of less effective induction of intestinal TRPV6 and calbindin D9K by 1,25(OH)2 Vitamin D
	(c) The ability of PTH to induce 1a-hydroxylase decreases with age
	(d) a, b, & c
	(e) b & c only

e

37. It is important that blood calcium levels stay within a normal range because:

Question 37 options:

	(a) Calcium antagonizes voltage-gated sodium channels, preventing spontaneous firing of neurons and tetany
	(b) Calcium antagonizes voltage-dependent calcium channels, preventing spontaneous firing of neurons and tetany
	(c) Low blood calcium (hypocalcemia) will cause excess calcium ions to block voltage-dependent sodium channels, causing weakness
	(d) Low blood calcium causes parathyroid tumours
	(e) None of the above

a

38. Hypercalcemia (blood ionized calcium concentrations elevated above normal): 

Question 38 options:

	(a) Can occur whenever people exceed the UL for calcium intakes in the diet and can result in symptoms after only a few days
	(b) Is caused by excessive dietary intakes in the majority of cases since the resulting overactivation of Vitamin D causes excessive absorption of calcium from the gastrointestinal tract that is poorly regulated
	(c) Is caused by excessive parathyroid hormone (PTH) secretion (i.e. hyperparathyroidism) in the majority of cases
	(d) Causes tetany due to increased spontaneous firing of neurons
	(e) a & c only

c

39. Calcium:

Question 39 options:

	(a) Is lost daily in the urine, feces, and from the skin
	(b) Excess in the diet can cause constipation
	(c) Loss can be increased by high sodium intakes, or by caffeine
	(d) All of the above
	(e) None of the above

d

40. Why is it important to ensure that biomedical research, including research on links between vitamin & mineral metabolism and disease, includes racially diverse groups: 

Question 40 options:

	(a) Because symptoms that are detectable in people with lower skin melanin contents (e.g. a flushing or redness response in the skin) may not be easily detectable in people with higher skin melanin contents, and therefore reliance on such symptoms could cause people to fail to detect a dangerous condition
	(b) Because susceptibility to deficiency in micronutrients such as Vitamin D can vary depending on the content of melanin in the skin
	(c) Because in the modern world, the global mobility of populations can allow people to move rapidly from a place where they may not experience a high degree of micronutrient deficiency risk, to a place where that risk of deficiency increases significantly, and public health systems must be aware of this to provide adequate health services to all members of the community
	(d) All of the above
	(e) None of the above

d