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NM - 302 > Calcium and Phosphorus > Flashcards

Calcium and Phosphorus Flashcards

1
Q

What is unique about Calcium valence electrons ?

A

2+, lost readily in solution
large effective radius
attracts H2O

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2
Q

What is the calcium generally considers for in the body?

A

a tool or carrier (messenger)
initiates a series of processes

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3
Q

Bone mineralization is a huge storage for

A

99% of calcium
80-90% of phosphorus

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4
Q

Only 1% of Calcium is ionized and is responsible for?

A

Blood clotting - Platelets
Enzyme regulation - calmodulin
Blood clotting, nerves, muscles,
membrane permeability - bind membranes and change conformation

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5
Q

What is the purpose of IP3 (inositol triphosphate) and DAG

A

signal transduction and lipid signaling

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6
Q

How is IP3 made, what does it do?

A

Through phosphorylation of PI and hydrolysis of PIP2 (cofactor magnesium)
Allows more intracellular calcium by binding the channel

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7
Q

How can calcium leave the cytoplasm of a cell?

A

Through Na+ or Mg+ pumps/ ATPase or can be sequestered into cells (ER, mito, nucleus)

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8
Q

Unique characteristics of phosphorus

A

found in the bone as hydroxyapatite Ca10(OH)2(PO4)6
preferred ionic state is orthophosphate as HPO4 and H2PO4

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9
Q

at pH 7.4

A

ratio is 4:1
HPO4 (basic) to H2PO4 (acidic)

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10
Q

Biological fxn of Phosphate

A

Bone mineralization
Electrolyte homeostasis
Structural role (phosphates, DNA/RNA - alt with pentose sugars)
Secondary messenger - kinase, phosphates, cAMP
Vit B metabolism

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11
Q

How can phosphate act as a buffer?

A

by collecting H+ and decreasing acidity inside the cell

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12
Q

3 ways calcium can be absorbed small I

A

Duodenum - Transcellular (major route) - Rq, energy + channel+ BPcalbindin — stim by low Calcium and calcitriol (Vit D)
illenum/jejunum - paracellular - energy independent (passive), depends on concentration
Colonic fermentation - fibers release Ca2+ (4-10% can be absorbed this way)

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13
Q

How is phosphate absorbed by the body

A

Absorbed linearly as HPO4, similarly to Ca2+
- Diffusion
-Carrier mediated with Mg / Na

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14
Q

How effective is absorption in comparison of Calcium to Phosphate

A

Calcium is 20-30%
Phosphate is 60-70%

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15
Q

What controls PTH production and secretion

A

plasma Ca 2+

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16
Q

What are the actions of PTH

A

Stimulates bone osteoblast – trigger breakdown
Stimulates kidney tubular cells to increase Ca2+ absorb
Stims kidneys to increase conversion to in kidneys to Active Vit D
Increase in intestine + bloodstream absorb

  • Actions are indirectly done via second messenger
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17
Q

How is phosphate affected with increase PTH to kidney tubular cells?

A

There is a decrease in re-absorption = increase in urine

18
Q

What is calcitonin, where it is released? Function?

A

Secreted from the thyroid glad (front of neck)
Releases when Ca2+ is HIGH
Increase Ca2+ storage/mineralization
reduce kidney/intestine/ bloodstream absorption
Vit D inhibited

19
Q

What is the purpose of bone remodeling 10% of the bone ever year?

A

Allow support of the body/ done defects
Incubate developing immune cells
Act as a reserve inorganic minerals
maintains optimal level of calcium in the blood

20
Q

Osteroclast vs Osteoblast

A

Clast = Clash of Clans = destroy and resorb old bone
B = Build = deposit new bone
“Coupled” but with bias on Clast

21
Q

Bone remodeling cycle has two phases describe each

A

Activation phase: conversion of osteoclast precursor to active (40days) rq calciotropic factors (Vit D, PTH, prolactin, RANKL)

Reversal phase: Bone resorption to formation (145 days) rq anabolic factors (estrogen, calcitonin, calcium, Osteoprotegrin)
- Osteoprotegrin enzyme inhibits bone breakdown

22
Q

Where does must reabsorption of phosphorus take place vs calcium

A

P: proximal tubule by activated sodium-phosphate cotransporter - linear relationship with excretion
C: Paracellular (b/c bound to albumin its harder)

23
Q

List all factors that decrease calcium absorption and excretion

A

Ab: fibre, phytate, oxalate, cations (Zn,Mg), excess unab fats
Ex: increase plasma phosphate = decrease in ionic Ca2+ = increase in PTH (increase absorption)

24
Q

Excess calcium can interrupt absorption of

A

iron and fatty acids

25
Q

List all factors that decrease phosphate absorption and excretion

A

Ab: phytate (legumes), excess Ca, Mg, Al
Ex: depletion, parathyroidectomy, calcitriol

26
Q

List all factors that increased calcium absorption and excretion

A

Absrob: PTH, Estrogen, Calcitriol (Active Vit D), Sugars , proteins
Excrete: sodium, Sulfur AA , caffeine

27
Q

List all factors that increase phosphate absorption and excretion

A

Ab: Calcitriol
Ex: PTH, Excess, estrogen, Thyroid hormones, phosphatonins

28
Q

How do phosphatonins like FGF-23 affect phosphorus excretion

A

secreted from osteocytes in bone and suppress sodium-phosphate cotransporters
Also suppresses CYP27B which makes calcitriol

29
Q

why are formula fed infants a concern in regards to calcium

A

reduced bioavailability and they need Ca2+ retention to support bone growth peak

30
Q

RDA / AI for calcium

A

Infants — 200-260mg (AI)
Teens — 1300 mg
Adults - 1000mg
Adult F >50 - 1200mg

31
Q

RDA for Phosphorus

A

Infants — 100-275mg (AI)
Teens - 1250mg
Adults - 700mg

32
Q

Food sources of Phosphorus

A

Almost everywhere: dairy product, meat, fish, eggs = 70% of intake
also processed foods & soda

33
Q

Chrons disease

A

Intestinal disorder, fat malabsorption

34
Q

Why does an inverse relationship exist between calcium and hypertension

A

They have reciprocal effects on hormone system and BP

35
Q

Preeclampsia

A

Decreased turnover of calcium metabolism = increased intracellular Ca2+, decreases ATP activity

36
Q

Describe causes of Hypocalcemia & consequences

A

Causes: Inadequate Vit D production, PTH resistance, Vitamin D resistance
Consequences: Fatigue, Neuromuscular irritability

37
Q

Describe causes and consequences of Hypercalcemia

A

Causes: Hyperabsorption of Ca due to high PT, Decreased urinary excretion, Increased bone resorption due to high PTH, Severe dehydration
Consequences: Fatigue, nausea, kidney stones

38
Q

What is the difference b/w Osteoporosis Type I vs Type II

A

Type I: Primarily menopausal women, 50-70, wrist and spine, Women 6:1
Type II (Senile): 70 >, Hip, Women 2:1

39
Q

Where would you likely see a Phosphorus deficiency or excess

A

Pre-term babies, low P diet + supplements

Excess: Concern in pop with compromised kidney fxn

40
Q

Phosphorus deficiency would occur where?

A

Re-feeding syndrome: catabolism = increase plasma phosphate, eat = Cells uptake P for use of energy during depletion = rapid depletion of P from plasma

Hyperventilation + respiratory alkalosis

Alcoholic: decrease P intake + poor absorption + disorganization of muscle

41
Q

Describe causes and consequences of Hypophosphatemia

A

Causes: Vit D deficiency or resistance, Increased urinary loss, Intracellular shifts of P from serum into cells
Consequences: CNS irritability, Muscle myopathy, Metabolic abnormalities

42
Q

Describe causes and consequences of hyperphosphatemia

A

Causes: Decreased urinary excretion, Acute P load
Consequences: Hypocalcemia - By binding to calcium which is then excreted. If secondary to renal disorders - hyperparathyroidism

NM - 302 (7 decks)

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