Metalloproteins

                Proteins are aminoacid polymers. In addition to the protein part most of the proteins contains some non-protein component. Such proteins are known as ' conjugated proteins". The protein part is known as "apoprotein". The non-protein component is known as "prosthetic group". If the prosthetic group is a metal atom then the conjugated protein is known as " metalloprotein".
                Metalloproteins are classified on the basis of their function as folloes:

• Respiratory proteins
• Electron transport proteins
• Metal storage proteins
• Catalytic proteins

I . RESPIRATORY PROTEINS :
                      These are metalloproteins which are involved in gas transport. Example : Hemoglobin, Myoglobin, Hemerythrin and Hemocyanin. Both hemoglobin and myoglobin are heme (prosthetic group) proteins containing Fe2+ . In higher animals hemoglobin transports oxygen from lungs to tissues. Myoglobin stores the oxygen in the tissues. Hemerythrin and hemocyanin are the oxygen carrying proteins of lower animals. Hemerythrin is a nonheme iron containing protein. Hemocyanin is a nonheme copper containing protein.

II . ELECTRON TRANSPORT PROTEINS :
                       These are metalloproteins which are involved  in electron transport. They are the components of electron transport chain (ETC). Example: Cytochromes, iron sulphur protein and blue copper protein. Cytochromes (a, b, c) are the iron containing heheproteins that act as electron carrier in all aerobic forms of life. Iron sulphur proteins (Rubredoxin, ferridoxin) are nonheme proteins involved in electron transfer. Blue copper proteins (stellocyanin, plastocyanin, azurin) are nonheme copper containing proteins involved in electron transfer.

III . METAL STORAGE PROTEINS :
                        These are metalloproteins which are used to store the surplus metal in nontoxic form. Example: Ferritin, Transferrin (iron storage protein) Ceruloplasmin (copper storage protein).

IV . CATALYTIC PROTEINS :
                          Enzymes are otherwise known as catalytic proteins. Many enzymes contain metal ions as their structural component. Example: Cytochrome oxidase (iron and copper), Super oxide dismutase (copper and zinc), Nitrogenase (iron and molybdenum). These enzyme are bimetalcomplexes.

Excess and defiency of trace metals

COPPER :

1. Copper deficiency results in loss of weight and death.
2. Severe deficiency of copper causes demineralization of bones.
3. Copper deficiency produces anemia. This cannot be treated by administration of iron.
4. Copper deficiency results in hypopigmentation of skin.
5. Copper deficiency produces Menke's disease or Kinky or Steel hair syndrome. Its symptoms are anemia and depigmentation of hair.
6. The formation of elastin and collagen are impaired in copper deficiency.
7. Copper deficiency results in the myocardial fibrosis.
8. Wilson's disease is associated with low levels of copper and ceruloplasmin in the blood and increased copper deposition in kidney, liver, brain, and comea.
9. Abnormal levels of serum copper leads to irritation of the gastrointestinal tract.

ZINC :

1. Zinc deficiency results in dwarfism.
2. There is loss of taste.
3. Zinc deficiency causes poor growth and loss of appetite.
4. Zinc deficiency produces dermatitis (lesions in the skin ).
5. Zinc deficiency leads to the formation of immature gonads (sex glands).
6. Deficiency of zinc obstracts the storage and secretion of insulin and causes diabetes mellitus.
7. Zinc deficiency is associated with myocardial infarction and cirrhosis of liver.
8. Zinc toxicity is associated with nausea (vomitting), gastric ulcer, anemia and excessive salivation.

IRON :

1. Iron deficiency leads to anemia. In such conditions the hemoglobin content of blood becomes 5-9g / 100ml of blood.(normal level of hemoglobin is 15 %).
2. Iron deficiency leads to giddiness.
3. In severe cases there may be oedema of the ankles.
4. Iron deficiency leads to loss of appetite and retarted growth.
5. iron toxicity leads to excessive deposition of iron in ferritin and hemosiderin (iron storage proteins). This disorder is known as hemosiderosis. This is common in patients receiving repeated blood transfusions.
6. Iron toxicity produces another disorder known as hemochromatosis. Accumulation of iron in liver, pancreas and skin produces cirrhosis (liver disorder), bronze diabetes and bronze-state pigmentation respectively. 

       
MANGAANESE :

1. Manganese deficiency leads to retarded growth and bone deformities.
2. Severe manganese deficiency leads to sterility.
3. Its deficiency leads to accumulation of fat in liver.
4. Deficiency of manganese results in the abnormal functioning of central nervous system.
5. Manganese deficiency causes increased activity of serum alkaline phosphatase.
6. Reduced activity of pancreas is associated with manganese deficiency. So insulin production is reduced.
7. Manganese deficiency in plants affects photosynthesis.
8. Manganese toxicity produces symptoms similar to Parkinson's disease.

MOLYBDENUM :

1. Deficiency of molybdenum results in lowered growth and increased mortality rate.
2. Its deficiency affects nitrogen fixation in plants.
3. Its deficiency affects plant growth.
4. Toxicity of molybdenum is known as molybdenosis. The symptoms are diarrhoea, anemia and impairment in growth.
5. Toxicity of molybdenum produces copper deficiency.

COBALT :

1. Cobalt deficiency causes anorexia (loss of desire to eat).
2. Its deficiency produces fatty liver (liver disorder).
3. Cobalt deficiency results in macrocytic anemia (anemia due to large size of red blood cells)
4. Cobalt deficiency produces hemosiderosis of spleen.
5. Cobalt toxicity causes polycythemia (increased number of red blood cells).

Inorganic chemistry

BIO-INORGANIC CHEMISTRY:
               Bio-onorganic chemistry ia an interdiscipilanary area of inorganic chemistry and biology. Bio-inorganic chemistry deals with the study of the role of inorganic elements in biochemical process. Nearly thirty elements of the periodic table are found to be essential for life processes. Their deficiency leads to serious disorders. Such elements are known as essential elements. Among them twenty one elements are needed in very small amounts. They are called as trace elements or micronutrients. Example : Iron, Copper, Cobalt, Manganese, Zinc, Molybdenum, Chromium, Iodine etc.
ROLE OF METALS IN BIOLOGICAL SYSTEM:
                Metal ions of proteins and enzymes can do many specific functions in biological processes. Some metals function as cofactors for many enzymes. The role of metal ions in the biological system may be given as follows.
I ) SODIUM :

1. Sodium is the major cation of the extracellular fluid.
2. Along with chloride and bicarbonate, sodium regulates the body's acid-base balance.
3. It maintains osmotic pressure and protects the body against excessive fluid loss.
4. It maintain the normal water balance and distributions.
5. It is involved in the absorption of glucose, galactose and amino acids from the small intestine.
6. It maintains the normal neuromuscular functions.
7. It is necessary for initiating and maintaining heart beat.
8. It functions in the permeability of the cells.

II) POTASSIUM :

1. Potassium maintains intracellular osmotic pressure.
2. It plays an important role in the regulation of acid-base balance in the cell.
3. It regulates the water balance in the cells.
4. It is essential for protein biosynthesis by ribosomes.
5. The enzyme pyruvate kinase requires K + for optimal activity.
6. Extracellular K+ influences cardiac muscle activity.
7. Potassium is required for the transmission of nerve impulse.
8. It influences muscle activity.

III) CALCIUM :

1. Calcium along with phosphorus is essential for the formation and development of bones and teeth.
2. Calcium ion is required in the blood coagulation process.
3. It is essentisl for nerve impulses and muscular contraction.
4. It regulates the permeability of membranes.
5. It functions as second and third messenger for some hormones.
6. The release of certain hormones from the endocrine glands is facilitated by calcium ions.
7. The cell to cell communication mau also require calcium ions.
8. Calcium ion act on myocardium and prolongs systole.
9. It required for the activation of several enzymes such as succinate dehyrogenase and ATPase. (Adenosine Triphosphatase)

IV) MAGNESIUM:

1. Magnesium is required for the formation of bone and teeth.
2. Magnesium ion is necessary for proper neuromuscular functions.
3. Magnesium ion serves as a cofactor for several enzymes requiring ATP such as hexokinase etc.
4. It is an integral part of certain enzymes such as co-carboxylase.
5. If functions as a cofactor for oxidative phosphorylation.
6. It is essential for maintaining osmotic pressure and water balance.
7. It is present in chlorophyll and hence it is essential for photosynthesis.

V) COPPER:

1. Copper is necessary for the synthesis of hemoglobin.
2. It is required for melanin (the pigment of hair and skin) formation.
3. It is required for the synthesis of phospholipid and collagen (structural protein0
4. Development of bone and nervous system requires copper.
5. Copper is a constitution of several enzymes such as tyrosinase, cytochrome oxidase, ascorbic acid oxidase etc.
6. It is a constituent of superoxide dismutase (antioxidant) amine oxidase etc.
7. Hemocyanin, a copper protein complex in invertebrates, functions like hemoglobin for oxygen transport.
8. Plastocyanins are the copper containing proteins found in photosynthetic organisms.
9. Azurins are blue copper proteins involved in electron transfer in the respiratory chain of some bacteria.

VI) ZINC :

1. Zinc is necessary to maintain the normal levels of vitamin A in blood.
2. Zinc is an essential component of several enzymes such as carbonic anhydrase, alcohol dehydrogenase etc.
3. The storage and secretion of insulin from pancreas requires zinc.
4. Zinc is required for wound healing.
5. Gusten, a zinc containing protein of the saliva is important for taste sensation.
6. Zinc is essential for proper reproduction.
7. Superoxide dismutase is a zinc cointaining enzyme. It acts as an antioxident.
8. Biosynthesis of mononucleotides and their incorporation into the nucleic acids require zinc.
9. Zinc is essential for normal growth.

VII) IRON :

1. Hemoglobin, the heme protein acts as the oxygen carrier from lungs to tissues.
2. Myoglobin, the heme protein stores the oxygen in the muscle.
3. There are many heme cointaining enzymes such as catalases, peroxidases etc.
4. Some enzymes require iron for their activity. Examples: xanthine oxidase, succinate dehydrogenase etc.
5. Cytochromes are the heme cointaining proteins involved in electron trasnsport chain.
6. Iron-sulphur proteins such as rubredoxin are involved in electron transfer reactions.
7. Hemerythrin is an non-heme iron protein used to transport and store oxygen in marine invertebrates.

VIII) MANGANESE:

1. Manganese is essential for normal bone formation.
2. It is essential for reproduction and normal growth.
3. It is essentisl for the synthesis of hemoglobin.
4. Manganese inhibites lipid peroxidation.
5. It is required for the normal functioning of central nervous system.
6. It is necessary for cholesterol biosynthesis.
7. It is involved in the synthesis of glycoproteins.
8. It act as a cofactor for many enzymes like enolase, arginase etc.

IX) MOLYBDENUM :

1. It is an essential constituent of the enzymes such as xanthine oxidase, aldehyde oxidase etc.
2. Nitrate reductase is a molybdenum containing plant enzyme required for nitrogen fixation.
3. It influences copper metabolism.
4. The bacterial enzyme hydrogenase requires molybdenum for its activity.
5. This element is essential for plant growth, because of its role in nitrogen fixation.

X) COBALT :

1. It is an essential component of vitamin B12.
2. Enzymes like ribonucleotide reductase require vitamin B12 for activity.
3. Cobalt is required to maintain normal bone marrow function.
4. Cobalt containing vitamin B12 ia an essential nutrient for humanbeings.