This document discusses calcium and phosphorus. Calcium is mainly found in bones and teeth and is obtained through foods like milk, cheese, and vegetables. About 40% of dietary calcium is absorbed in the small intestine through active transport involving vitamin D. Calcium levels in the blood are tightly regulated by hormones like parathyroid hormone and calcitonin to maintain homeostasis. Conditions like hypercalcemia and hypocalcemia can occur if calcium levels become too high or low.

1. BIOCHEM 612
CALCIUM AND PHOSPHORUS

2. CALCIUM
• Calcium is an important mineral mainly found
in bone and teeth.
Dietary sources: It is widely distributed in food
substances such as milk, cheese, egg-yolk,
beans, lentils, nuts, figs, cabbage.
Distribution in the body
0.1% in ECF 99% in bones 0.5% in soft tissues

3. Absorption:
• Calcium is taken in the diet principally as
calcium phosphate, carbonate.
• About 40 per cent of average daily dietary
intake of Ca is absorbed from the gut by
1. Simple diffusion
2. An “active” transport process involving
energy and Ca++ pump.
 Both the processes require 1, 25-di hydroxy-
D3 (calcitriol).

4. CALCIUM IN PLASMA
• The normal level of plasma calcium is 9-11
mg/dl.
The calcium in plasma is of 3 types
Plasma protein bound
calcium (41%)
Complexed Calcium,
(9%)
Calcium in ionised form
(50%)

5. Calcium exchange and homeostasis
Ca intake (1000mg/day)
ECF
(1300 mg)
Cells
(1300mg)
Kidneys
Intestine
900mg/day
Absorption
(350mg/day)
Secretion
(250mg/day)
Reabsorption
(9880mg/day)
Filtration
(9980mg/day)
Urine= 100mg/day
Bones
Deposition
(500mg/day)
Resorption
(500mg/day)
Depends on
calcium status of
the blood

6. Regulation of calcium homeostasis
Hormonal regulation of calcium homeostasis
• Parathormone (PTH)
• Calcitonin
• Vit.D3

8. Functions
• Calcium plays a role in blood coagulation by
producing substances for thromboplastic activity
of blood.
• Calcium has a role in neuromuscular
transmission.
• Needed for excitability of nerves.
• Calcium plays role in muscle contraction.
• Normal excitability of heart is Ca ion
dependent.

9. CLINICAL IMPORTANCE
• The two conditions namely Hypercalcaemia and
Hypocalcaemia occur.
I. Hypercalcaemia
When the serum calcium level exceeds 11.0
mg/dl, it is called as hypercalcaemia .
• What is normal concentration ?
• Causes
1. Primary hyperparathyroidism:
2. Malignancy
3. Renal failure

10. • II. Hypocalcaemia
Hypocalcaemia is said to exist when serum calcium is less than 8.5 mg/dl
as determined by a standard method.
Causes: The commonest causes of hypocalcaemia are
• Hypoparathyroidism
• renal failure.
• surgically-induced hypoparathyroidism.
• Malnutrition, malabsorption states
• Renal Diseases and Renal Failure

11. Class Activities
• What are major key players in the regulation
of calcium homeostasis?
• What is inactive form of vit.D3.
• What is the site of synthesis of 25,hydroxy
cholecalciferol?