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IHN: Biochemistry 2 > calcium > Flashcards

calcium Flashcards

(56 cards)

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1
Q

bioavailability of caclium is affected by

A

dense food matrix

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2
Q

high bioavailability
low bioavailability

A

high bioavailability = dairy
low bioavailability = green-leafy vegetables

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3
Q

factors that reduce bioavailability of calcium

A
  1. dietary fiber
  2. phytic acid
  3. oxalate
  4. divalent cations (Zn, Cu)
  5. unabsorbed fatty acids (FFA)
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4
Q

calcium must be in __/__ form to be absorbed

A

calcium must be in ionic/free form to be absorbed (Ca2+)

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5
Q

__ pH facilitates formation of __ calcium

A

low pH facilitates formation of ionic calcium

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6
Q

fractional Ca2+ absorption is percent of Ca2+ absorbed by __ from __ Ca2+

A

fractional Ca2+ absorption is percent of Ca2+ absorbed by intestine from oral load Ca2+

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7
Q

young adults fractional Ca2+ absorption

A

25-30%

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8
Q

fractional Ca2+ absorption decrease with __ and increases with __

A

fractional Ca2+ absorption decrease with age and increases with 1st trimester of pregnancy

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9
Q

2 methods of calcium absorption

A
  1. transcellular, carrier-mediated transport process (saturable)
  2. paracellular, passive diffusion process
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10
Q

calcium absorption is mediated by

A

calcium absorption is mediated by vit D

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11
Q

vit D induces expression of (4)

A
  1. TRPV6
  2. Calbindin
  3. PMCA1b
  4. NCX1
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12
Q

transcellular, carrier mediated transport steps

A
  1. TRPV6 moves Ca2+ into cytosol of enterocyte
  2. Calbinidin D9K binds absorbed Ca2+ and transports it to basolateral membrane
  3. PMCA1b (Ca2+ dependent ATPase) pushes Ca2+ into portal circulation
  4. Calbindin brings Ca2+ to NCX1 (Na+, Ca2+ exchanger), pushes 1 Ca2+ out and one Na+ in
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13
Q

paracellular, passive diffusion

A

Ca2+ cross epithelial barrier btwn cells due to presence of occludins, paracellin-1, and claudins (creates a tunnel for Ca2+

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14
Q

vit D induces expression of

A

paracellin-1

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15
Q

50% of Ca2+ in systemic and portal circulation is bound to
the rest is

A

albumin or pre-albumin
the rest is free

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16
Q

do pregnant women need more Ca2+

A

yes

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17
Q

upper limit __ as we age

A

upper limit decreases as we age

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18
Q

__% of calcium filtrated in the kidney is reabsorbed

A

98% of calcium filtrated in the kidney is reabsorbed

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19
Q

__ is responsible for 90% of reabsorption

A

passive diffusion is responsible for 90% of reabsorption

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20
Q

reabsorption in kidney occurs in
70%
20%

A

reabsorption in kidney occurs in
70%: proximal tube
20%: ascending loop of Henle

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21
Q

remaining 10% of calcium is reabsorbed via __

A

remaining 10% of calcium is reabsorbed via active transport

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22
Q

which method of calcium reabsorption is more important?

A

10% via active transport
bc it ensures calcium absorption during scarcity

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23
Q

resorption of calcium in the kidney

Study These Flashcards
A
  1. TRPV5 absorbs Ca2+ into renal epithelial cells
  2. Calbindin D28K binds reabsorbed Ca2+ and transports it to basolateral membrane
  3. PMCA1b and NCX1 push Ca2+ into blood
  4. Paracellin-1 allows Ca2+ to passively diffuse from urine to blood
24
Q

only __% of filtered Ca2+ is excreted

Study These Flashcards
A

only 1-2.5% of filtered Ca2+ is excreted

25
pregnant and lactating women reabsorb __ calcium bc calcium reabsorption is regulated by __ and __
pregnant and lactating women reabsorb **more** calcium bc calcium reabsorption is regulated by **vit D** and **estrogens**
26
__ allows passive diffusion of Ca2+ from __ to __
**Paracellin-1** allows passive diffusion of Ca2+ from **urine** to **blood**
27
2 physiological roles of calcium
1. structural function 2. protein activation
28
calcium in structural function
hydroxapatite and calcium carbonates in bones
29
protein activation by calcium (2)
1. direct (annexing, blood clotting enzymes, phospholipase A2) 2. mediated by Ca2+ as a second messenger (calmodulins, calpains, protein kinase C)
30
calcium signaling mechanism
1. stimulus binds receptor 2. activates G-protein cascade, activates phospholipase C (PLC) 3. PLC converts phospolipid to inositol-P3 (InsP3) 4. InsP3 targets ER or SR (organelles that sequester calcium) 5. InsP3 binds ryanodine receptor (RyR) 6. Ca2+ binds cytoplasmic calmodulin upon release from ER and SR 7. active calmodulin targets Ca2+ sensitive kinases 8. Ca2+ is extruded by Na/Ca exchanger or PMCA
31
2 methods of Ca2+ extrustion from cell
1. Na/Ca exchanger (secondary active) 2. PMCA (active transport)
32
skeleton contains __% of calcium
skeleton contains **99**% of calcium
33
calcium plays a huge role in makeup of
bones and teeth
34
hormones that regulate calcium and phosphate
PTH vit D calcitonin
35
PTH is secreted when Ca2+ levels are
PTH is secreted when Ca2+ levels are **low**
36
PTH target tissues (3)
kidney bone intestine
37
in kidney, PTH effects PTH induces increased __ reabsorption and decreased __ reabsorption PTH induces production of active vit D which increases intestinal absorption of __
in kidney, PTH effects PTH induces increased **Ca2+** reabsorption and decreased **PO4 3-** reabsorption PTH induces production of active vit D which increases intestinal absorption of **BOTH Ca2+ and PO4 3-**
38
PTH induces bone resorption to __ circulating Ca2+ levels
PTH induces bone resorption to **increase** circulating Ca2+ levels
39
PTH action on intestine relies on
vit D
40
bone remodeling cycle
1. PTH induces resorption: osteoclasts dig into bone, release Ca and phosphorous 2. reversal: mononuclear cells occupy the depression 3. monnuclear cells recruit pre-osteoblasts to occupy depression 4. bone formation: osteoblasts release collagen, Ca2+, PO4 3- to form new bone (mineralization) 5. minerlization: new osteoblasts are buried in crystal structure and become osteocytes
41
RANKL-RANK-OPG pathway controls
bone resorption
42
in RANKL-RANK-OPG, PTH is catabolic/anabolic
PTH is **catabolic**/anabolic
43
__ direct/drive bone resorption (breakdown), but __ do the actual activity of resorption
**osteoblasts** direct/drive bone resorption (breakdown), but **osteoclasts** do the actual activity of resorption
44
OPG-RANKL-RANK pathway
1. growth factors, PTH, cytokines induce osteoblasts to produce M-CSF, RANK ligand (RANKL) and OPG 2. when enough M-CSF binds pre-osteoclast receptors, osteoclast matures 3. RANKL binds RANK on mature osteoclast, osteoclast differentiates and is activated 4. osteoclasts produce HCL and cathespins which resorb bone and release Ca2+ and PO4 3- 5. osteoblasts release OPG which binds RANKL and prevents it from activating RANK receptors (prevents excess bone resorption)
45
osteoblasts release __ which binds RANKL and prevents it from activating __ to prevent excess bone resorption
osteoblasts release **OPG** which binds RANKL and prevents it from activating **RANK** to prevent excess bone resorption
46
estrogen promotes __ which __ bone resorption
estrogen promotes **OPG expression** which **reduces** bone resorption
47
PTH is both
anabolic (bone formation) and catabolic (bone resorption)
48
PTH is both
anabolic (bone formation) and catabolic (bone resorption)
49
PTH stimulates osteoblasts to release __, which triggers bone resorption by allowing __ to be released into bloodstream
PTH stimulates osteoblasts to release **RANKL**, which triggers bone resorption by allowing **Ca2+** to be released into bloodstream
50
what hormone corrects calcium deficiency
PTH
51
the __ and __ of PTH exposure deermine net effect on bone mass (cata or ana)
the **duration** and **periodicity** of PTH exposure deermine net effect on bone mass (cata or ana)
52
continuous exposure to PTH = __ effects seen in __ of bone remodeling cycle
continuous exposure to PTH = **catabolic** effects seen in **first 3 weeks** of bone remodeling cycle
53
intermittent, low doses of PTH = __ effects seen in __ of bone remodeling cycle
intermittent, low doses of PTH = **anabolic** effects seen in **last 3 months** of bone remodeling cycle
54
factors causing low bone mineral density
1. low calium and vit D 2. unhealthy lifestyle 3. inadequate dietary protein levels
55
is calcium deficiency common?
no, bc we have large reserves in our body
56
chronic inadequate calcium intake causes
rickets osteoporosis

IHN: Biochemistry 2 (38 decks)

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