Phosphorus (The Fourth Macromineral)

Question 1

How much phosphorus is contained within the body?

Answer 1

1 kg

Question 2

Percentage of phosphorus in each part of the body

Answer 2

Bones and teeth = 80%
Muscles and cells = 10%
As chemical compounds = 10%

Question 3

Bound and free phosphorus percentages

Answer 3

Free and ionized = 40%
Complexed with Ca²⁺, K⁺, Mg²⁺ = 50%
Protein bound = 10%

Question 4

Sources of phosphorus

Answer 4

Milk, cereals, leafy vegetables, meat and eggs

Question 5

Fasting inorganic phosphate levels in adults

Answer 5

2.5-4.5 mg/dL

Question 6

Fasting inorganic phosphate levels in children

Answer 6

5.0-6.0 mg/dL

Question 7

Why is fasting plasma phosphate levels greater than postprandial (after a meal)?

Answer 7

Release of insulin draws phosphates in the cells along with glucose

Question 8

What is the metabolic role of phosphorus?

Answer 8

Osteoid tissue formation
Energy metabolism – formation of high energy compounds
As coenzymes – NAD, NADP, PLP
Mediator of hormone action - cAMP
Phosphorylation of enzymes
As phosphate esters – G-6-P, Phospholipids, Phospho-proteins
Buffering actions - in plasma and cells
In red cells – as component of 2,3-BPG

Question 9

How is phosphorus level regulated?

Answer 9

Controlled along with calcium via PTH and vitamin D₃

Question 10

Conditions which cause hyperphosphatemia?

Answer 10

Hypoparathyroidism and renal failure

Question 11

Conditions which cause hypophosphatemia?

Answer 11

Hyperparathyroidsim and Vitamin D resistant rickets