Bone Vitamin and MInerals

Question 1

Calcium Store

Answer 1

Hydroxyapatite Ca(PO4)2.

Question 2

Calcium function

Answer 2

Cofactor for alpha amylase and phospholipase

Question 3

Calcium absorbed

Answer 3

Passive absorption through tight junctions
Active absorption TRPV6 Ca2+ channel along duodenum and upper jejunum

1,25(OH)2D stimulated production of Calbindin (CaBP) which transports calcum to basolateral membrane

Question 4

Calcium reabsorption

Answer 4

In kidney at TRPV6 - Ca2+ channel

Question 5

Calcium absorption efficiency

Answer 5

Children -75%

Adults - 30%

Question 6

Short term deficiency of calcium

Answer 6

Not a measurement of dietary intake.
Means something is wrong hormonally
Low Plasma levels of Ca2+

Question 7

Long term calcium deficiency

Answer 7

Chronic Ca deficiency/ not absorbing

Shown as reduced bone mass and osteoporosis

Question 8

Excess Calcium

Answer 8

Hypercalcaemia – High blood Ca levels
Usually results from high vitamin D intake
If on supplements way more likely to go into excess compared with if consume that much in diet.
Increased risk of kidney stones

Question 9

Vitamin D Overview

Answer 9

Fat soluble

Two forms

Question 10

D2

Answer 10

Ergocalciferol
Plants
Less efficiency absorbed

Question 11

D3

Answer 11

Cholecalciferol

Animals

Question 12

Vitamin D Absorption

Answer 12

Fat soluble taken up by lipids in the gut
Transported to liver
Converted to 25(OH)D
Carrier protein added DBP
25(OH)D-DBP filtered out of blood by kidney
Reabsorbed by proximal convoluted tubule
Separated from transporter
 Binds to mitochondria
Hydroxylated by o	25(OH)D-1hydroxylase 
PTH released

Question 13

1,24(OH)2D genomic action

Answer 13

Binds to CDR and forms heterodimer RXR
Binds to VDRE on DNA
Influences – mineral homeostasis, vitamin D metabolism, cell differentiation, DNA replication

Question 14

1,24(OH)2D non-genomic action

Answer 14

Binds to Membrane bound receptors (MARRS)

Opens ion gated channels, increase intracellular Ca, activates protein kinase, adenylyl cyclase

Question 15

1,25(OH)2D in intestine

Answer 15

Ca and P absorption
Not known how
Increase rapidly
Increase activity of enzymes such as Ca-ATPase
Increase synthesis of some proteins

Question 16

1,25(OH)2D in bone

Answer 16

Normal bone growth
Effects osteoblasts directly
Effects osteoclasts indirect
Preosteoclast have a receptor called RANK
Which binds to ligand RABKL
Binds surface of osteoblast stimulating 1,25(OH)D

Question 17

Deficiency of Vitamin D

Answer 17

Rickets

Question 18

Phosphorus store

Answer 18

85% stored in bones Ca10(PO4)6(OH)2

rest in body

Question 19

Phosphorus Absorption

Answer 19

55-70%
Small intestine has enzymes that hydrolyse phosphate
Passes epithelial boarder via Na dependent phosphate co-transporter (NPTs)
PTH decrease activity
1,25(OH)2D and
Low plasma concentration increases activity

Question 20

Phosphorus deficiency

Answer 20

Rare
Hypophosphatemia
anorexia
anaemia
muscle weakness
Bone pain
Rickets and osteomalacia
Increased risk of infection

Question 21

Magnesium Overview

Answer 21

1/3 for metabolic activity

2/3 provide structure and support

Question 22

Magnesium function

Answer 22

Muscle contraction
Enzyme activity that require ATP utilise Mg
Act as an allosteric activator
Transport ions such as potassium and calcium across membranes
Oxidative phosphorylate
Glycolysis
DNA and protein synthesis

Question 23

Magnesium Absorption

Answer 23

Small intestine in jejunum and ileum
Active transport and paracellular absorption
50-60% absorbed
Inversely proportional to amount consumed
Vit D enhances absorption
Fibre and phosphorus decrease Mg absorption

Question 24

Assessment of Magnesium

Answer 24

Serum not a good indicator due to homeostatic control. There is research as to whether an ion-specific electrode would be a good indicator but currently use intracellular Mg levels in red blood cells.

Question 25

Sever magnesium deficiency

Answer 25

Hypomagnesemia
Hypocalcemia
Hypokalemia
Resistance to Vit D
Neuromuscular hyper excitability

Question 26

Moderate Magnesium deficiency

Answer 26

Cardiovascular disease
Elevated blood pressure
Osteoporosis
Diabetes

Question 27

Cardiovascular disease an magnesium link

Answer 27

anti-thrombotic
Coronary vasodilator
Anti-arrhythmic
Inhibits release of catecholamines

Question 28

Osteoporosis

Answer 28

Reduce Mg in bones

Leads to abnormal crystal formation