Minerals
Question 1. Functions of calcium.
Answer.
Functions Of Calcium
- Calcium is required for bone formation
- Calcium plays a role in muscle contraction. Calcium increases the interaction between actin and myosin
- Calcium is necessary for transmission of nerve impulse
- Calcium influences cell membrane structure
- Calcium plays a role in the transport of water and ions across the cell membrane
- Calcium activates the enzymes pancreatic lipase, ATPase and succinate dehydrogenase
- Calmodulin is a calcium binding regulatory protein. Calcium calmodulin complex activates the enzymes adenylate cyclase and protein kinase
- Certain hormones exert their action through the mediation of calcium and thus calcium acts as a second messenger or third messenger for such hormonal action e.g. – epinephrine and anti diuretic hormone
- Calcium is required for the release of certain hormones from the endocrine glands e.g. insulin, parathyroid hormone and calcitonin
Question 2.Factors affecting calcium absorption.
Answer.
Factors Affecting Calcium Absorption
Factors Which Increase Calcium Absorption
- Calcitriol (Vitamin D) induces the synthesis of calcium binding protein in the intestinal epithelial cells and increases calcium absorption
- Parathyroid hormone increases calcium absorption by increasing the synthesis of calcitriol
- Low pH (acidity) increases calcium absorption
- Lactose increases calcium absorption
- The amino acids lysine and arginine increase calcium absorption by increasing the solubility of calcium salts
- Sugars increase calcium absorption.
Organic acids produced by the fermentation of sugars in the intestine increase the solubility of calcium salts and hence increase calcium absorption
Factors Which Inhibit Calcium Absorption
- Phytates present in cereals form insoluble calcium salts and inhibit calcium absorption
- Oxalates present in vegetables like cabbage and spinach form insoluble calcium salts and inhibit calcium absorption
- High content of dietary phosphorus results in the formation of insoluble calcium phosphate and inhibits calcium absorption
- Free fatty acids inhibit calcium absorption by reacting with calcium to form insoluble calcium soaps. This is particularly observed when fat absorption is impaired
- High pH (alkaline conditions) inhibits calcium absorption
- High content of dietary fibers interferes with calcium absorption
- High content of magnesium in the diet decreases calcium absorption
- High content of iron in the diet inhibits calcium absorption.
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Question 3. Functions of iron.
Answer.
Functions Of Iron
- Iron is a constituent of haemoglobin and myoglobin which are required for the transport of oxygen and carbon dioxide
- Iron is a constituent of cytochromes which are required for the electron transport chain
- Catalase is an iron requiring enzyme Catalase destroys hydrogen peroxide
- Peroxidase is an iron requiring enzyme
Peroxidase breaks down hydrogen peroxide and is also required for phagocytosis (killing of bacteria) by neutrophils - Iron requiring enzymes are
- Xanthine oxidase
- Cytochrome reductase
- Acyl CoA dehydrogenase
Question 4 . Factors affecting iron absorption.
Answer.
Factors Affecting Iron Absorption
Factors Which Increase Iron Aborption
- Low pH (acidic pH) increases absorption
- Vitamin C and glutathione increase iron absorption
- Small peptides and amino acids increase iron absorption
- In iron deficiency anaemia iron absorption is increased 10 times more than normal
- Copper increases iron absorption
- Meat, chicken and fish increase iron absorption
Factors Which Decrease Iron Absorption
- Phytates present in corn, soya and cereals decrease iron absorption
- Oxalates, present in leafy vegetables and chocolates decrease iron absorption
- A diet with high phosphorus content decreases iron absorption
- Tea, coffee and eggs decrease iron absorption
- Dietary fibers decrease iron absorption
- Alkaline pH decreases iron absorption
- Impaired absorption of iron is found in malabsorption syndromes such as steatorrheoa
- In patients with partial or total surgical removal of stomach / intestine, iron absorption is impaired
- Parasitic infection (hookworm) decreases iron absorption
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