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OSSF 2 > Exam 3- Mineral Metabolism > Flashcards

Exam 3- Mineral Metabolism Flashcards

1
Q

what properties of calcium and phosphate make them well suited to altering the conformation and functional properties of proteins?

A

calcium: positive charge
phosphate: negative charge

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2
Q

what form of calcium is biologically active and what percentage of the total calcium in blood does it make up?

A

ionized calcium
about 50%

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3
Q

true/false: the amount of calcium in interstitial fluid bound to proteins is higher than the amount in blood

A

false: very little protein in interstitial fluid to begin with

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4
Q

free intracellular calcium concentrations must remain ______

A

low

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5
Q

what abnormality causes an increase in free, ionized calcium in blood?

A

acid-base abnormalities

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6
Q

what do changes in plasma protein concentration do to calcium levels in plasma?

A

increase total plasma calcium concentration, but not ionized calcium concentration

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7
Q

how do changes in anion concentration affect calcium?

A

change fraction complexed with anions: raises phosphate concentration, increasing calcium complexed to phosphate, decreasing the amount of free, ionized calcium

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8
Q

where is most of the phosphate that is not stored in bones located?

A

intracellularly

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9
Q

what happens to plasma phosphate in the kidney?

A

freely filtered and more than 85% reabsorbed

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10
Q

how do plasma phosphate concentrations trigger hormonal regulation?

A

decreased phosphate leads to calcitriol

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11
Q

what three organ systems take part in calcium homeostasis?

A

gastrointestinal tract
bone
kidney

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12
Q

what is the main determinant of intestinal absorption of calcium?

A

calcitriol (active vitamin D)

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13
Q

how does parathyroid hormone impact calcium homeostasis?

A

lower plasma calcium levels leads to release
increases bone resorption and decreases bone deposition
increases reabsorption calcium in the kidneys
increases absorption calcium in gastrointestinal tract through activation vitamin D

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14
Q

where is most of the body’s calcium stored?

A

in the skeleton: about 99%

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15
Q

how is 99% of the bone calcium and phosphate stored?

A

calcium phosphate crystals: hydroxyapatite
important structural component of bone

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16
Q

where is the rest of the calcium and phosphate in bone stored?

A

salts in equilibrium with interstitial fluid

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17
Q

how much of the skeleton does cortical/compact bone make up?

A

80%

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18
Q

cortical bones is composed of repeating units called __________

A

osteons

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19
Q

where is extracellular fluid stored in bone?

A

canaliculi between lacunae (osteocytes within)

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20
Q

what are the four types of cells in bone tissue?

A

osteoblasts
osteocytes
osteogenic stem cells
osteoclasts

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21
Q

what cells take part in bone remodeling?

A

osteoblasts build up and osteoclasts resorb

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22
Q

from where are osteoclasts derived?

A

monocyte/macrophage lineage (not osteogenic precursor cells)

23
Q

how do osteoclasts resorb bone?

A

release organic acids which dissolve crystals of calcium phosphate and proteolytic enzymes which dissolve collagen

24
Q

what does the bone cells layer have?

A

osteocytes
has calcium and phosphate transporters which are hormonally regulated

25
Q

how is calcium absorbed from the intestinal lumen (what routes)?

A

paracellular and transcellular

26
Q

how is calcium absorbed transcellularly?

A

Ca-ATPase pump and Ca/Na exchanger

27
Q

where is calcium reabsorbed in the kidney and is it regulated?

A

60% in proximal tubule: paracellular and unregulated
distal convoluted tubule: transcellular and regulated

28
Q

true/false: calcium bound to protein is handled by the kidneys

A

false: only ultrafilterable

29
Q

what does parathyroid hormone do to activate or inactivate vitamin D?

A

stimulates 1-alpha hydroxylase in the epithelial cells of the proximal tubule of the kidney to form biologically active form of vitamin D

30
Q

what cells release parathyroid hormone?

A

chief cells of the parathyroid gland

31
Q

how does parathyroid hormone affect phosphate handling?

A

indirectly decreases plasma phosphate levels

32
Q

what causes a release of calcitonin?

A

increased plasma calcium

33
Q

what does calcitonin do?

A

inhibits osteoclasts and bone resorption

34
Q

true/false: the concentration of calcium in milk is 3-4x higher than plasma

A

true

35
Q

what is calcium important in?

A

excitable cells
role in blood coagulation
role in regulating function of enzymes and secretion of hormones
component of 2nd messenger systems

36
Q

what is phosphate important in?

A

structural component of nucleic acids and phospholipids
inorganic phosphate needed for synthesis organic phosphates- ATP
many biological pathways
kinases are enzymes that attach phosphate groups
phosphatases are enzymes that remove phosphate groups

37
Q

how do the ratios of calcium bound to proteins, bound to complexes, and free, in plasma and interstitial fluid compare?

A

most in both is free
a lot in plasma is bound to proteins too
more, but still small, bound in complexes in interstitial fluid

38
Q

how does an intracellular calcium signal arise?

A

ion channels in cell membrane
endoplasmic reticulum releases

39
Q

where are lacunae and what is in them?

A

between concentric lamellae
osteocytes

40
Q

what are osteoblasts formed from?

A

osteogenic stem cells

41
Q

what do osteocytes do?

A

maintain bone tissue

42
Q

what separates the bone fluid from the plasma?

A

osteocyte layer with calcium and phosphate transporters that are hormonally regulated

43
Q

where is calcium reabsorbed in the kidney passively and paracellularly? what percent?

A

proximal tubule
60%

44
Q

what is the reabsorption of calcium in the distal convoluted tubule like?

A

transcellular and regulated

45
Q

true/false: about 5% of filtered calcium is excreted in urine

A

false: 1-3%

46
Q

what does the active form of vitamin D do?

A

binds to intracellular receptors in target tissues to regulate transcription of genes related to Ca++ transport

47
Q

what does parathyroid hormone do to phosphate blood levels?

A

lowers them

48
Q

do mammary epithelial cells have a lot of free calcium in the cytosol?

A

no

49
Q

what do kinases do?

A

attach phosphate groups

50
Q

what do phosphatases do?

A

remove phosphate groups

51
Q

how much of the calcium in blood is free and ionized?

A

50%

52
Q

how can calcium move across membranes?

A

primary or secondary active transport

53
Q

how do acid-base abnormalities change free ionized calcium?

A

changes amount bound to albumin: increased H+ means less calcium bound to albumin means increased free ionized calcium

54
Q

what is the most important effect of calcitriol?

A

increases absorption of calcium from the intestine

OSSF 2 (19 decks)

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