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IHN: Biochemistry 2 > FINAL: phosphorous > Flashcards

FINAL: phosphorous Flashcards

1
Q

is there phosphorous in our cells?

A

NO

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2
Q

food sources of phosphate

A

animal proteins
cereals
legumes

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3
Q

2 most abundant body minerals

A
  1. calcium
  2. phosphate
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4
Q

85% of phosphate is found in __ as __

A

85% of phosphate is found in bone as calcium phosphate aka hydroxyapatite (crystal bone)

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5
Q

15% of phosphate is found in __ as (4)

A

15% of phosphate is found in skeleton as:
phosphoproteins
phospholipids
nucleotides
nucleic acids

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6
Q

0.1% of phosphate is found in __ which is important for __

A

0.1% of phosphate is found in extracellular fluid which is important for pH

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7
Q

__% of phosphate from protein is absorbed

A

70-90% of phosphate from protein is absorbed

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8
Q

phosphate in grain is __

A

phosphate in grain is phytate/phytic acid

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9
Q

__% of phosphate in grain is NOT absorbable
__% in potatoes/tubers

A

80% of phosphate in grain is NOT absorbable
35% in potatoes/tubers

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10
Q

problem with phytic acid

A

phytic acid is negative and traps cations (Ca, Zn, Fe, Cu)

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11
Q

excess phytic acid + __ = deficiency

A

excess phytic acid + poor phosphate intake = deficiency

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12
Q

RDA for phosphate increases in __
RDA does not increase in __

A

RDA for phosphate increases in childhood
RDA does not increase in adulthood

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13
Q

why is RDA higher for children?

A

they are growing their skeletons

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14
Q

is phosphorous a nutrient of concern?

A

No

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15
Q

does phosphorous have an upper limit? if so, why?

A

Yes, because if kidneys don’t work well, phosphate filtration won’t work well

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16
Q

intestinal absorption of phosphate occurs via __

A

intestinal absorption of phosphate occurs via Npt2

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17
Q

what type of transporter is Npt2?

A

facilitated co-transporter (symporter)

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18
Q

Npt2 is __ depdent and is found on __ side of intestine

A

Npt2 is sodium depdent and is found on apical side of intestine

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19
Q

Npt2 is upregulated by

A

vitamin D

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20
Q

lage amount of __, __, and __ (__) can decrease phosphorous absorption

A

lage amount of Ca, Mg, and Al (antacids) can decrease phosphorous absorption

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21
Q

do we lose a lot of phosphate in feces?

22
Q

__% of dietary phosphate is absorbed

A

50-80% of dietary phosphate is absorbed

23
Q

steps of phosphate absorption by enterocyte

A
  1. organically bound phosphate –> Pi (by phospholipase alkaline phosphatase)
  2. Pi absorbed by enterocyte through Npt2b
  3. Pi to blood
24
Q

3 options for Pi in blood

A
  1. Pi complex with other minerals (Ca, Na, Mg) (5%)
  2. Pi complexed + found as oganic phosphate (70%)
  3. free PO4 3- (25%)
25
Q

phospholipase alkaline phosphatase
secreted by __
activated by __

A

phospholipase alkaline phosphatase
secreted by enterocyte
activated by calcitriol (vit D)

26
Q

phosphate is __ soluble so it is typical found in the __ in __

A

phosphate is water soluble so it is typical found in the blood in solution

27
Q

more __ in diet = incresaed phosphate absorption
more __ in diet = decreased phosphate absorption

A

more protein in diet = incresaed phosphate absorption
more grain in diet = decreased phosphate absorption

28
Q

Npt2b is increased by __ and __

A

Npt2b is increased by vit D and low Pi diet

29
Q

high Pi diet what happens to enterocyte absorption of Pi

A

Pi saturates transporters, passive paracellular transport occurs

30
Q

phosphate levels are mainly regulated by

31
Q

phosphate and hormones cascade

A
  1. low Ca2+ = parathyroid releases PTH
  2. PTH induces formation of vit D
  3. vit D = increased absorption of Ca and phosphate
  4. PTH causes:
    1. increased bone resorption (more Ca and phosphate in circulation)
    2. increase resorption of Ca in kidney, decreased phosphate resorption (more phosphate in urine)
32
Q

for phosphate homeostasis, a lot of phosphate is released into __ and __

A

for phosphate homeostasis, a lot of phosphate is released into feces and urine

33
Q

we want bone __ = bone __

A

we want bone resorption = bone deposition

34
Q

in adulthood, bone __ > bone __

A

in adulthood, bone resorption > bone deposition

35
Q

structural phosphate properties

A
  1. P + Ca = hydroxyapatite
  2. nucleotides (DNA + RNA)
  3. phospholipids
36
Q

regulatory phosphate properties

A
  1. molecule trapping (G6P)
  2. reversible covalent modification of proteins (kinases)
  3. forming high energy molecules (ATP, creatine phosphate)
  4. regulate acid-base balance (extracellular: urine, blood)
37
Q

overview phosphate properties

A

bone/membranes
energy (DNA, RNA)
energy in muscle

38
Q

Ca + P signaling pathways steps

A
  1. stimulus (hormone) activates PLC (GTP –> GDP)
  2. PIP2 releases InsP3 as a secondary messenger
  3. InsP3 targets Ca channels in ER + sarcoplasmic reticulum –> Ca release
  4. target calmodulin –> activate kinases
  5. kinases produce phosphate to activate several events
39
Q

phosphate excretopn mainly in __
__-__% (depends on __)

A

phosphate excretopn mainly in urine
0.1-20% (depends on diet)

40
Q

resorption of phosphate occurs in

A

proximal tubule

41
Q

resorption in apical, brush border is via __ which is __ diffusion

A

resorption in apical, brush border is via Npt2a+2c which is active diffusion

42
Q

resorption in proximal tubules via Npt2a+2c is dependent on

A

pH and sodium

43
Q

in basolateral membrane, resorption of phosphate is via

A

facilitated diffusion

44
Q

hormones involved in phosphate

A
  1. PTH
  2. 1-25-dehydroxy vitamin D3
  3. calcitonin
  4. FGF23 (fibroblast growth factor 23 - osteoporosis)
  5. estrogen, insulin
45
Q

increased calcitriol = __ phosphate absorption and serum levels

A

increased calcitriol = increased phosphate absorption and serum levels

46
Q

phosphate homeostasis steps

A
  1. vit D controls FGF23 release from bone
  2. FGF23 receptor partners with Klothko in kidney
  3. increased phosphate urinary excretion
  4. decreased serum phosphate
47
Q

FGF23 in bone = suppressed __ and __ cotransporters = increased

A

FGF23 in bone = suppressed Npt2a and Npt2c cotransporters = increased renal excretion of phosphate

48
Q

FGF23 in bone = suppressed renal expression of __ = decreased __ = decreased __ absorption = decreased serum __

A

FGF23 in bone = suppressed renal expression of 1-alpha hydroxylase = decreased calcitriol = decreased phosphate absorption = decreased serum phosphate

49
Q

in presence of PTH + FGF23, Npt2a+2c cotransporters are relocalized from __ to __ which __ transport activity

A

in presence of PTH + FGF23, Npt2a+2c cotransporters are relocalized from plasma membrane to vesicles which blocks transport activity

50
Q

hormone overview (all inclusive)

A
  1. low Ca2+ = PTH release
  2. PTH blocks phosphate transport in kidneys (less resorption)
  3. PTH stimulates formation of vit D (in enterocyte)
  4. vit D induces absorption of Ca + P in enterocyte (more Ca + P in circulation)
  5. vit D targets bone to release FGF23
  6. FGF23+Klothko block phosphate transporter (phosphate lost in urine)
  7. FGF23 targets alpha-1 hydroxylase and prevents more vit D formation
  8. FGF23 from bone prevents more PTH release from parathyroid gland
51
Q

phosphate deficiency who is at risk

A
  1. preemies
  2. lots of antacids (Ca, Mg, Al)
  3. malnourished ppl being re-fed enterally or parenterally without added phosphorous (re-feeding syndrome)
  4. X-linked hypophosphatemia + rickets (Dent’s syndrome: poor phosphate absorption in kidneys)

IHN: Biochemistry 2 (38 decks)

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