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IHN BIOCHEMISTRY FINAL > 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
phospholipase alkaline phosphatase secreted by __ activated by __
phospholipase alkaline phosphatase secreted by **enterocyte** activated by **calcitriol (vit D)**
26
phosphate is __ soluble so it is typical found in the __ in __
phosphate is **water** soluble so it is typical found in the **blood** in **solution**
27
more __ in diet = incresaed phosphate absorption more __ in diet = decreased phosphate absorption
more **protein** in diet = incresaed phosphate absorption more **grain** in diet = decreased phosphate absorption
28
Npt2b is increased by __ and __
Npt2b is increased by **vit D** and **low Pi diet**
29
high Pi diet what happens to enterocyte absorption of Pi
Pi saturates transporters, passive paracellular transport occurs
30
phosphate levels are mainly regulated by
CALCIUM
31
phosphate and hormones cascade
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
for phosphate homeostasis, a lot of phosphate is released into __ and __
for phosphate homeostasis, a lot of phosphate is released into **feces** and **urine**
33
we want bone __ = bone __
we want bone **resorption** = bone **deposition**
34
in adulthood, bone __ > bone __
in adulthood, bone **resorption** > bone **deposition**
35
structural phosphate properties
1. P + Ca = hydroxyapatite 2. nucleotides (DNA + RNA) 3. phospholipids
36
regulatory phosphate properties
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
overview phosphate properties
bone/membranes energy (DNA, RNA) energy in muscle
38
Ca + P signaling pathways steps
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
phosphate excretopn mainly in __ __-__% (depends on __)
phosphate excretopn mainly in **urine** **0.1**-**20**% (depends on **diet**)
40
resorption of phosphate occurs in
proximal tubule
41
resorption in apical, brush border is via __ which is __ diffusion
resorption in apical, brush border is via **Npt2a+2c** which is **active** diffusion
42
resorption in proximal tubules via Npt2a+2c is dependent on
pH and sodium
43
in basolateral membrane, resorption of phosphate is via
facilitated diffusion
44
hormones involved in phosphate
1. PTH 2. 1-25-dehydroxy vitamin D3 3. calcitonin 4. FGF23 (fibroblast growth factor 23 - osteoporosis) 5. estrogen, insulin
45
increased calcitriol = __ phosphate absorption and serum levels
increased calcitriol = **increased** phosphate absorption and serum levels
46
phosphate homeostasis steps
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
FGF23 in bone = suppressed __ and __ cotransporters = increased
FGF23 in bone = suppressed **Npt2a** and **Npt2c** cotransporters = increased **renal excretion of phosphate**
48
FGF23 in bone = suppressed renal expression of __ = decreased __ = decreased __ absorption = decreased serum __
FGF23 in bone = suppressed renal expression of **1-alpha hydroxylase** = decreased **calcitriol** = decreased **phosphate** absorption = decreased serum **phosphate**
49
in presence of PTH + FGF23, Npt2a+2c cotransporters are relocalized from __ to __ which __ transport activity
in presence of PTH + FGF23, Npt2a+2c cotransporters are relocalized from **plasma membrane** to **vesicles** which **blocks** transport activity
50
hormone overview (all inclusive)
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
phosphate deficiency who is at risk
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 FINAL (15 decks)

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