Phosphorus

phosphorus makes up how much of body weight (%)?

0.8- 1.2%

phosphorus:

____% found in skeletal tissue

___% found in soft tissue

___% found in blood

85%

14%

1%

what sources is phosphorus found in?

widely found

animal sources (protein, rich)

plant sources (good, nuts, seeds, beans)

_______ in cola can be a _____

phosphoric acid

significant contirbutor

most Phos is absorbed as ___________

inorganic phosphate ions

Organic bound Phos is ______ influenced

enzymatically

organic bound phosphorus is bound to what?

phospholipids 

what must occur to Phos in phospholipids?

must be hydrolyzed from glycerol phosphate bond

what enzyme hydrolyzes glycerol phosphate bond from phospholipids

phospholipase C

phospholipase C is dependent on

zinc

what enzyme is stimulated by calcitriol in brush border

Alkaline phosphatase (zinc dependent)

what does alkaline phosphatase do? and location?

frees phosphate from other bound forms in the brush border 

body absorption is based on __%

body's need

what % of phosphorus is absorbed?

50--70%

absorption occurs primarily in the ___ & ___

duodenum & jejunum

absorption in the duodenum and jejunum occurs via what ways  (3)

via carrier mediated, active transport & passive diffusion

when does passive diffusion occur? where?

due to typically high inorganic phosphate concentration and acidic pH in duodenum

what would lower pH for passive diffussion

with presence of dihydrogen phosphate

active transport occurs at ____ intake via ____________

low intake

sodium phosphate co-transporter

what can occur to phosphate absorbed

-complexed w/ other minerals (Ca, Na, Mg)

-complexed and found as organic phosphate

phosphate absorbed passively as what forms?

PO4 (free) and as dihydrogen phosphate 

absorption enhanced by

vit D

absorption inhibited by

phytate

excessive intake: Mg, Ca, Aluminum (competition)

transport into blood occurs via

facilitated diffusion

In what forms in organic phosphate found in the body

Phospholipids

Lipoproteins

PO4

H2PO4 (dihydrogen phosphate)

What % of organic phosphate is found as phospholipids and lipoproteins

70%

remaining 30% is mostly as ____ which is greatly soluble in water, with lesser amounts as __________

Less amount as ______ complexed with ____________________

HPO4

H2PO4

H2PO4 complexed with Ca, Mg, or Na

smaller % of HPO4 is complexed with  

Ca, Mg, or Na

what can influence serum Phos concentration (5)

age

dietary Phos

PTH

fibroblast growth factor

renal function

__% of Phos found in bones & teeth

85%

in which cells is Phos found

in every cell

Phos functions as/in (5)

ATP

nucleic acids (DNA, RNA)

Phospholipids

second messenger system

acid base balance

___% of Phos found in soft tissue

15%

out of the 15%, how much of phos found in striated muscle

half

relationship between PO4 and Ca in blood

inversely related to Ca

phos functions do what as we age

decrease w/ age

In bone, the ratio of Ca to P is .... (amorphous)

1.3:1 (various amorphous Ca P forms)

_____ is the non-amorphous crystalline form of Ca and Pho

Hydroxyapatite

ratio of ca to Phos in hydroxyapatite (non-amorphous crystalline form) 

1.5:1 to 2.0:1

_____, ______, and ______ influence phosphorus balance in body

PTH, calcitriol, and calcitonin

low Phis is known as

hypophosphatemia

in hypophosphatemia, what does the body do?

• stimulates 1-alpha hydroxylase activity

• increase absorption, increase bone resorption, and renal reabsorption

• increase plasma phosphorus without increase in calcium causes increase excretion of calcium

hypophosphatemia, stimulates 

1-alpha hydroxylase activity

hypophosphatemia affects on absorption, resorption, etc (3)

increase absorption, increase bone resorption, and renal reabsorption

increase in plasma phosphorus w/out increase in _________ causes (related to excretion) 

calcium

increased excretion of calcium 

high phos is reffered to as

Hyperphosphatemia

when we have Hyperphosphatemia, what does our body do? (2)

- stimulates Calcitonin & inhibits 1-alpha-hydroxylase & stimulates 24-hydroxylase

- decreases intestinal Ca & P & bone absorption, decreases Ca & P resorption

when we have hyperphosphatemia, calcitonin inhibits what and stimulates what hormone 

inhibits 1-alpha-hydroxylase & stimulates 24-hydroxylase

when we have Hyperphosphatemia, what 3 things occur (think absorptive)

decreases intestinal Ca & Phos absorption

decreases bone absorption

decreases Ca & P resorption

in Hyperphosphatemia what occurs in intestines

decreases intestinal Ca & Phos absorption

in Hyperphosphatemia what occurs in bone

 decreases bone absorption

in Hyperphosphatemia what occurs in kidneys

decreases calcium and phosphorus reabsorption

Phos as part of ____ acts on activation of____ _____within cell

cAMP

protein kinases

how is phos involved in intermediary metabolism?

via cAMP and controlling phosphorylation and dephosphorylation of enzymes associated with glycogen breakdown, fatty acid oxidation, transamination, etc.

what critical role does Phos play?

critical in role of vitamins as coenzymes (thiamin diphosphate, pyridoxal phosphate)

what enzyme plays a role in hemoglogin-oxygen saturation

1,3 diphosphoglycerate (dependent on phosphorus) 

Urine excretion %

67-90%

feces excretion %

10-33%

reabsorption of Phos occurs in what organ (and what structure)

kidney’s proximal tubules

reabsorption of Phos in proximal tubules involves (relies on what)

sodium phosphate cotransporter

unlike calcium, higher dietary Phos leads to....

higher blood Phos & higher urinary excretion

(will pull calcium with it)

Higher urinary excretion of Phos occurs due to what scenarios (3)

high P intake, PTH & acidosis

inhibition of urinary losses occurs due to (6)

low phos intake

alkalosis

calcitriol

estrogen

growth hormone

Thyroid hormone

Deficiency of phos occurance

rare

phos deficiency contributes to

• bone loss

• decrease in growth (tooth)

• rickets, anorexia, wt loss, renal dysfunction

• weakness, irritability, bone pain, low cardiac output, neurological problems (not needed)

Food sources of Phos

dairy, bakery, meats (various)

some from food additives

Phos and its limitation 

most difficult to limit intake

RDA for adults

Daily value

700mg/d; current intakes exceed

1000mg

deficiency is how common

very rare; highly unlikely

who is at risk for deficiency? (5)

- pre-mature babies

- alcoholics

- elderly w/ poor diets

- chronic diarrhea

- use of aluminum antacids (binds to P)

UL

3-4g/d

Toxicity is a problem for who

individuals w/ inefficient kidney function

P ions can bind to ___

Ca

Ca-P precipitates in...

body tissues

if Ca is low, what can occur?

compound bone loss

assessment of Phos

• Due to the rare case of deficiency, it is not considered for assessment accuracy

• Most often, both serum and urinary levels are assessed however issues of specificity or sensitivity are questionable.

• Serum levels are misleading and are ill reflective of tissue concentrations