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Endocrine #3 > Biological Functions of Calcium, Magnesium, and Phosphorus (Toribio) > Flashcards

Biological Functions of Calcium, Magnesium, and Phosphorus (Toribio) Flashcards

1
Q

Use correct terminology
Match the following with the appropriate organ:
1. Absorption -
2. Reabsorption -
3. Resorption -

A
  1. Intestine
  2. Kidney
  3. Bone
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2
Q

A mare with a foal may show signs of?

A

hypocalcemia

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3
Q

Which two elements have similar behaviors in the biological system?

A

Magnesium & Calcium

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4
Q

Is a naturally occurring mineral (calcium phosphate mineral) form of calcium apatite that shows good biocompatibility and is an excellent candidate for bone repair and substitution

A

Hydroxyapatite

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5
Q

(T/F) The skeleton contains approximately 99% of the total body calcium as hydroxyapatite crystals [(Ca10(PO4)6(OH)2

A

True

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6
Q

(T/F) Phosphorus (or phosphate) represents ~1% of the body weight, with most (85%) located in the bone matrix (hydroxyapatite), 15% in blood and soft tissues, and less than 0.1% in the extracellular fluid

A

True

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7
Q
  • Alkaline Metal
  • 5th most abundant element in the body
  • about 1.5% of the body weight is calcium
  • Is found in 3 main compartments:
    - Skeleton (99%)
    - Soft tissue/cell organelles (0.9%)
    - Extracellular fluid/ Plasma (0.1%)
    What element was that describing?
A

Calcium

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8
Q

Which of the following is correct?
A. Oxygen > Calcium > Carbon > Nitrogen > Hydrogen
B. Oxygen > Nitrogen > Carbon > Hydrogen > Calcium
C. Oxygen > Carbon > Hydrogen > Nitrogen > Calcium

A

C. Oxygen > Carbon > Hydrogen > Nitrogen > Calcium

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9
Q

The free or the ionized calcium is going to make up about ______% of the total calcium in the blood

A

55

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10
Q

What are the 3 forms that plasma total calcium exists?

A
  • Bound to proteins such as albumin (40-45%)
  • Ionized = free, active Ca2+ (50-55%)
  • Complexed to anions: lactate, bicarbonate, and phosphate (5%)
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11
Q

________ blocks Na+ from getting into cells = Blocks depolarization

A

Ca2+ (Na+ channel antagonist)

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12
Q

Striated muscle = needs ____________ Ca2+

A

intracellular

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13
Q

Neurons and smooth muscle = need ______________ Ca2+

A

extracellular

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14
Q

Calcium binding to proteins is pH-dependent
(T/F) In acidosis there is increased binding = increased plasma Ca2+

A

False, decreased binding

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15
Q

Calcium binding to proteins is pH-dependent
(T/F) In alkalosis there is increased binding = decreased plasma Ca2+

A

True

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16
Q

In acidosis, the hydrogens will displace Mg2+ and Ca2+ from albumin, then when you measure the total calcium, it is the same. But what would not be the same?

A

Active calcium (you have more free calcium)

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17
Q

(T/F) Most Ca absorption occurs in the large intestine

A

False, small intestine

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18
Q

(T/F) ~40-70% of the calcium in the diet is absorbed

A

True

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19
Q
  • Phytate
  • Oxalate
  • Phosphate (chelation)
    What do these elements do?
A

Reduce calcium absorption

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20
Q

Absorption is:
Passive, non-saturable, concentration-dependent, voltage-dependent

A

Paracellular

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21
Q

Absorption is:
Active, saturable, concentration-independent, needs energy, more regulated

A

Transcellular

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22
Q

What are the 3 steps of Transcellular?

A

1- Apical entry
* Epithelial calcium channels – (ECaC = TRPV)
2- Cytoplasmic diffusion:
* Calbindin D9k and D28k
3- Basolateral extrusion:
* Plasma membrane calcium ATPase (PMCA)
* Sodium/Calcium exchanger (NCX)

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23
Q

Renal Handling of Calcium
(T/F) ~70% of calcium is reabsorbed in distal tubules

A

False, proximal tubules

24
Q

Renal Handling of Calcium
(T/F) ~20% of calcium is reabsorbed in the ascending loop of Henle

A

True

25
Q

Renal Handling of Calcium
(T/F) ~5-10% of calcium is reabsorbed in the distal tubules and it is paracellular

A

False, Transcellular

26
Q

(T/F) Most calcium reabsorption is Transcellular

A

False, Paracellular

27
Q
  • Non-metal, anion
  • 6th most abundant element in the body
  • about 1% of body weight
  • Concentrations are higher in growing animals and alkaline phosphatase is also higher in young animals
  • Found in 3 main compartment
    - Skeleton (85%)
    - Soft tissues (15%)
    - Extracellular fluid (0.1%)
    What element was that describing?
A

Phosphorus

28
Q

What form of phosphorus is the one measured clinically in blood samples?

A

Inorganic (30%)
*The other 70% part is bound to the cells

29
Q

Phosphorus Functions
*As part of phospholipids is essential for cell membrane stability
*As part of ATP/GTP/energy – muscle contraction, hormone secretion, enzyme activation, energy, and electrolyte regulation
*As part of cAMP is essential for cell signaling
*It is part of nucleic acids (DNA, RNA)
*In oxygen transport (2,3-diphosphoglycerate)

A

Non-structural (phosphorus as a regulatory ion)
- the 15%

30
Q

Phosphorus Absorption
(T/F) ~20-60% of phosphorus in the diet is absorbed depending on species, requirements, and age

A

True

31
Q

Phosphorus Absorption
(T/F) Most phosphorus absorption occurs in the proximal small intestine and large intestine

A

False, distal small intestine

32
Q

Phosphorus Absorption is:
cotransporter-dependent, requiring sodium

A

Transcellular

33
Q

(T/F) Multiple factors influence intestinal phosphorus reabsorption including requirements, age, diet composition, factors in the diet, and hormones*

A

False, absorption

34
Q

(T/F) Multiple factors influence renal reabsorption of phosphorus including requirements, age, and hormones (PTH, FGF-23, vitamin D*)

A

True

35
Q

Phosphorus reabsorption is ___________________

A

Na-dependent

36
Q

Most (80%) phosphorus reabsorbed in ____________ tubules
- Transcellular
3 steps: apical entry, cytoplasmic diffusion, basolateral extrusion

A

proximal

37
Q
  • Divalent cation, alkaline metal
  • 11th most abundant element in the body
  • ~0.05% of the body weight
  • It is found in 3 main compartments:
    - Skeleton (60%)
    - Soft tissues (38%)
    - Extracellular fluid (2%)
    What element was this describing?
A

Magnesium

38
Q

(T/F) In blood, most magnesium is in plasma

A

True

39
Q

Total magnesium exists in 3 forms:

A

1- Bound to protein such as albumin (30%)
2- Ionized = free, active (60%)
3- Complexed to anions: lactate, bicarbonate, and phosphate (10%)

40
Q

Magnesium Functions
* Cofactor for >300 enzymes/enzymatic reactions
* Important for energy metabolism
* Important for cell membrane stability
* Essential for transmembrane ion transport (e.g. Na+/K+ ATPase)
* Any process that requires ATP/energy also requires Mg2+
* Nucleic acid synthesis requires Mg2+
* Essential for calcium homeostasis
** PTH synthesis and PTH receptor activation require Mg2+**

A

Non-structural (magnesium as a regulatory ion)
- the 40%

41
Q

Magnesium Absorption
(T/F) ~30-50% of magnesium in the diet is absorbed

A

True

42
Q

Magnesium Absorption
Most magnesium absorption occurs in the small intestine, except in:

A

ruminants where most magnesium absorption occurs in the rumen

43
Q

What are the elements in the diet that reduce magnesium absorption?

A
  • Excessive phosphates
  • Oxalates
  • Fatty acids
44
Q

Renal Handling of Magnesium
(T/F) ~20% of Mg is reabsorbed in proximal tubules

A

True

45
Q

Renal Handling of Magnesium
(T/F) ~60% of Mg is reabsorbed in the ascending loop of Henle

A

True

46
Q

Renal Handling of Magnesium
(T/F) ~5% of Mg is reabsorbed in the proximal tubules

A

False, distal tubules (Transcellular)

47
Q

What are the factors that influence magnesium concentrations?

A
  • Electrolytes (calcium, phosphorus)
  • Acid-base status (acidosis/alkalosis) similar to Ca2+
  • Hormones (PTH, insulin)
  • Plasma proteins (albumin in particular)
48
Q

Most in the skeleton; ionized calcium (Ca2+) is active form; most absorption in small intestine; most reabsorption in PCT; multitude of functions; affected by pH

A

Calcium

49
Q

Most in the skeleton; organic/inorganic; inorganic is measured clinically; most absorption in distal SI and large intestine; most reabsorption in PCT; a multitude of functions; higher in young animals

A

Phosphorus

50
Q

Most in the skeleton; ionized magnesium (Mg2+) is active form; most absorbed in the small intestine (and rumen); most reabsorption in DCT; a multitude of functions; Mg2+ affected by pH; important for calcium homeostasis

A

Magnesium

51
Q

Of the different forms of calcium in circulation, which one is influenced by albumin concentrations?

A

Total calcium

52
Q

(T/F) A high pH increased the binding of calcium to albumin

A

True

53
Q

(T/F) Acidosis increases binding of calcium to plasma proteins

A

False

54
Q

(T/F) Phosphorus is important in energy generation and electrolyte transport

A

True

55
Q

(T/F) Processes that require ATP also require magnesium

A

True

56
Q

What is an explanation as to why animals with hypocalcemia may become hyperexcitable?

A

Low extracellular calcium promotes Na+ entry into excitable cells

Endocrine #3 (8 decks)

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