INORGANIC BIOMOLECULES
Essential & Non-Essential Elements
Essential elements are those elements which are required for the maintainance of life of plants &animals.
Absence of these elements results in death or a severe malfunction of the organism.
Example- Oxygen,hydrogen,nitrogen,calcium,phosphorus etc.
Non essential elements are those elements which don”t play any positive role in biological systems.
Absence of these elements does not affect the body of an organism.
Essential elements
Bulk Elements
Trace Elements
Bulk elements:- They are the elements which are found in higher concentrations.Trace elements:-They are those elements which are needed in very low concentations.
Essential Bulk elements SODIUM
Major cation of extra cellular fluid in animals.
Important in nerve functioning in animals.
Major component of vertebrate blood.
NaCl helps in osmotic regulation of body & tissue fluids.
Na+ ions also serves as essential activating ions for specific enzyme activity.
Potassium
Maintains the electrolyte balance in your body's cells.
Manages your blood pressure and keeps your heart functioning properly.
Assists nervous system by aiding in the correct function of tissues needed for sending nerve impulses.
Aids in the waste removal process.
Enhances muscle control, the growth and health of your cells.
Calcium & Magnesium
Present as carbonates &phosphates in the skeletal structure of mammals as about 99% of Ca2+ &70% Mg2+ .
Calcium essential for blood clotting. Calcium stabilizes blood pressure. Calcium contributes to normal brain
function. Magnesium is required for all living
cells It is catalyst for numerous biological reaction involving the release of energy.
Mg is a constituent of bone. Magnesium presence in extracellular
regulates the transmission of nerve impulses.
Also present in chlorophyll.
Iron
Iron is one of the metals found in greatest abundance in biological systems in the form of porphyrin complexes such as haemoglobin & myoglobin.
Of total iron in the human body,70% is present in haemoglobin & about 3%in myoglobin.
Most of the remaining iron is stored as ferritin. Ferritin is major iron storage protein in mammals but is also found in
plant chloroplasts. Distributed mainly in spleen,liver &bone marrow.
Essential Trace Elements
Pathway of Fe2+ from food stuffs to haemoglobin and to ferritin involves the following mechanism:-
I. FE3+ OF DIETERY MATERIAL IS REDUCED TO FE2+ IN THE GASTROINTESTINAL TRACT.
II. AFTER ABSORPTION INTO THE CELLS OF THE INTESTINAL MUCOSA,FE2+ IS INCORPORATED INTO FERRITIN AS FE3+ .
III. THE FE2+ IN MUCOSA IS ALSO CONVERTED TO FE3+ PLASMA.
IV. PLASMA FE3+ IS IN EQUILIBRIUM WITH IRON IN THE LIVER,SPLEEN & BONE MARROW.
Copper
Cu Is a constituent of redox enzymes &hemocyanin.
The Cu in hemocyanin protein is oxygen carrier & supplies oxygen to certain aquatic creatures &redox enzymes.
Cu containing enzymes plays an important role in the pigmentation of skin,functioning of brain &in iron,metabolism in body in hemoglobin formation.
Deficiency of cu in human system develops an Anemia. Because of excess of copper,a person suffers from Wilson’s disease. Wilson”s disease:- Autosomal recessive genetic disorder with onset in the 2ndor 3rd decade. Onset in children aged 4-5yrs is also reported but rarely. Excess Cu is deposited in excess in the liver,kidney or brain.
Cobalt-: Cobalt is also essential trace element which is essential for many organisms including mammals. A.)Activates number of enzymes.B.) Highly toxic to plants.
IodineA. Iodine is critical for formation of thyroid hormones T3, or
triiodothyronine, and T4, or thyroxine.B. Inadequate production of thyroid hormones can cause
enlargement of the thyroid gland, also known as goiter, while its deficiency during pregnancy can cause irreversible brain damage in newborns.
FluorideA. Well recognized for its role in forming bones and teeth,
fluoride is present in the body as calcium fluoride.B. Fluoride hardens tooth enamel, reduces incidence of tooth
decay and may prevent bone loss.
Zinc In addition to its role in formation of enzymes,
zinc improves immune function, helps clot blood, maintains sense of taste and smell.
keepYou can obtain sufficient amounts of zinc by regularly eating eggs, seafood, red meats, fortified cereals and whole grains.
Skin healthy and enables normal growth and development.
Chromium and Selenium Chromium is an important trace mineral that is
necessary for normal functioning of insulin, a hormone that maintains blood sugar levels.
It is also essential for metabolism of carbohydrates, proteins and fats.
Some important sources of chromium include liver, processed meats, brewer’s yeast, whole grains, cheese and nuts.
Selenium, along with vitamin E works as an antioxidant that prevents damage of cells, may prevent some cancers and is essential for the normal functioning of the thyroid gland.
Meat, seafood, nuts and cereals are good sources of selenium.
SOURCES OF ZINC
NICKEL • ESSENTIAL TRACE ELEMENT FOR PLANT UREASES.
• DEFICIENCY IN FOOD SLOWS DOWN THE FUNCTIONING OF LIVER IN CHICKS &RATS RAISED ON DEFICIENT DIET.
• HIGHLY TOXIC TO MOST PLANTS & MODERATELY TOXIC TO MAMMALS.
• CARCINOGENIC IF PRESENT IN LARGE CONC. IN BIOLOGICAL SYSTEMS.
ARSENIC:-• ULTRATRACE ELEMENT IN RED ALGAE,CHICK,RAT,PIG,GOAT &SOME MAMMALS
INCLUDING HUMANS.
• DEFICIENCY IN CHICKS RESULTS IN DEPRESSED GROWTH.
• MODERATELY TOXIC TO PLANTS &HIGHLY TOXIC TO MAMMALS WHEN PRESENT IN MORE THAN ULTRA TRACE ELEMENTS.
Porphyrins &Metalloporphyrins Porphines are macrocyclic rings made of four pyrolle rings linked
together through methane bridges.these porphines have pyrolle system with double bonds.therefore act as tetradentate ligands with nitrogen donor sites.
Two of these are tertiary nitrogen donor positions which can form coordinating bonds by donating a pair of electrons each to the metal ion.
The other two are secondary nitrogen donor positions,each of which can lose a proton in forming a coordinate bond with a metal ion.
Thus,a porphin ring can act a a tetradentate dinegative ligand. When the four pyrolle rings of porphin carry substituents other
than hydrogens,these are called porphyrins. These substituents are usually organic groups with electron
withdrawing or electron donating characteristics. The complexes in which a metal ion is held in the porphyrin ring
system are called Metalloporphyrins. The porphyrin ring system is rigid because of the delocalization of
electrons in the pyrolle rings. The nature of metalloporphyrins vary with the nature of the metal
ion &the type of organic substituents on the porphyrin structure.
Porphin Ligand(porphine)
Metal complex with porphin ligand (Metalloporphyrin)
Heme is an iron porphyrin which is present in hemoglobin and myoglobin.
Chlorophyll is magnesium complex of porphyrin which plays important role in the process of photosynthesis.
Photosynthesis is an important redox reaction occurring in nature to convert water & Carbon dioxide into carbohydrates &oxygen in the presence of solar energy.
In this metalloporphyrin,in addition to substituents,a double bond in one of the pyrolle rings is reduced to form magnesium dyhydrido porphyrin complex as shown in figure below:-
PHOTOSYNTHESIS PROCESS
Structures of heme &chlorophyll metaporphyrins
Iron porphyrins:-Hemoglobin & Myoglobin
Structure of Hemoglobin
Hemoglobin is a large protein with a molecular weight of about 64500.
Consists of four subunits each of which contains one heme group associated with protein globin.
Therefore,there are 4 heme groups bonded to four protein chains.one heme group with its protein is called subunit.
Froms alpha chains of 141 amino acids&two forms beta chains of 146 amino acids.
An outline structure of hemoglobin
Myoglobin is relatively a small protein of molecular weight of about 17000.
Consists of one polypeptide chain (globin) with one heme group (iron porphyrin complex) embedded their in.
The peptide chain consists of 150-160 amino acid residues folded about the single heme group as shown in figure.
Heterocyclic ring system of heme is porphyrin derivative containing 4 pyrolle rings labelled as A,B,C,D joined by methane bridges.
The Fe atom present at the centre of the heme is bonded by four porphyrin nitrogen atoms &one nitrogen atom from imidazole side chain of histidine residue.
Polypeptide chain plays an important role in biological fixation of Oxygen.
Structure of Myoglobin
Structure of myoglobin containing heme group
&polypeptide chain
ROLE OF HEMOGLOBIN & MYOGLOBINHemoglobin &myoglobin plays very important role in transporting oxygen from lungs to tissues & Carbon dioxide.
I. Oxygen is inhaled into the lungs at very high pressure where it binds Hb in the blood forming HbO2.
II. The oxygen is then transported to respiring tissues whre the partial pressure of O2 is low.
III. The O2 then dissociates from Hb & diffuses to the tissues where myoglobin picks it up &stores until it is needed.
IV. Myoglobin has a great affinity for O2 then Hb.
V. This increases the rate od diffusion of O2 from the capillaries to the tissues by increasing its solubility.
VI. The Hb & CO2 (as HCO3- ) are then returned to the lungs where CO2 is exhaled.
Myoglobin & hemoglobin functions &cooperativity• The main function of hemoglobin is to bind O2 at high partial
pressure of O2 found in the lungs &then carry it without any loss through the blood to the tissues where myoglobin picks up O2 from Hb.
• In the lungs,where the pressure of O2 is high &much O2 is bound,the affinity of heme fro O2 becomes very high .
• But when Hb reaches the cells where the pressure of O2 is low & O2 begins to dissociate from the complex.
• This information is passed on so that the remaining heme groups also unload their O2 groups.
• The myoglobin picks up all the O2.• Since myoglobin has only one heme group .it does not have
any cooperative binding so it does not lose its affinity fro O2.this shows that myoglobin has higher affinity for O2 then Hb at low partial pressure of O2 in the muscle.
Myoglobin & hemoglobin functions &cooperativity• The main function of hemoglobin is to bind O2 at high partial
pressure of O2 found in the lungs &then carry it without any loss through the blood to the tissues where myoglobin picks up O2 from Hb.
• In the lungs,where the pressure of O2 is high &much O2 is bound,the affinity of heme fro O2 becomes very high .
• But when Hb reaches the cells where the pressure of O2 is low & O2 begins to dissociate from the complex.
• This information is passed on so that the remaining heme groups also unload their O2 groups.
• The myoglobin picks up all the O2.• Since myoglobin has only one heme group .it does not have
any cooperative binding so it does not lose its affinity fro O2.this shows that myoglobin has higher affinity for O2 then Hb at low partial pressure of O2 in the muscle.
• Myoglobin has only one heme group per molecule &the binding between the iron &the oxygen molecule is similar to that in Hb but the equilibrium is simpler because only one oxygen molecule is bound.Its very interesting to study the oxygenation behavior vs oxygen pressure Po2 under physiological conditions for myoglobin & Hb.
The reversible binding of O2 to Mb may be represented by the simple equilibrium reaction:-
Mb + O2 MbO2 ……..(1)
The equilibrium constant K may be expressed as:-
K = [MbO2] [Mb] [O2] or K= [MbO2] ……………………(2) [Mb]P (P = Equilibrium partial pressure of oxygen)
Let us define a term fractional oxygen saturation ,θ which represents the Ratio of the concentration of the Mb present as MbO2 to the total concentration of Mb. i.e.
θ = [MbO2] …………….(3) [Mb]+[MbO2]
From eq. (2) & (3),we get,
K = θ (1-θ)P θ = KP 1+KP
This is the equation for the hyperbolic curve .This curve shows that as partial pressure of O increases,more of O2 binds to Mb.At very high partial pressure of O2,almost all the O2 binding sites are occupied &Mb is said to be saturated with O2.At a partial pressure of 2.88 torr,Mb is half saturated with O2. When Mb is half saturated θ is 0.5 so that partial pressure of oxygen, P1/2 is
K = θ
(1-θ)P1/2
K = 0
(1-0.5)P1/2
K = 1
P1/2
P1/2 (O2) = 1 KThus,at 0.5 or 50% saturation ,K is defined as inverse of partial pressure of O2 at 50% saturation (θ =0.5)Hb having four subunits has more complex behavior.Fractional oxygen saturation in case of Hb is given by the expression :
θ = kPn
1+kPn
The exact value of n depends upon the pH.The shape of the Hb binding curve is not like the hyperbolic curve of Mb.The HbO2 binding curve is described by sigmoid shape.
O2 binding curves for Mb & Hb with partial pressure of O2
The hemoglobin-O2 binding curve is of sigmoid type whereas the myoglobin – O2 curve is simple hyperbolic type.
Bohr”s Effect The variation of oxygen affinity with
the pH of the medium is called Bohr”s effect.
It is also called pH sensitivity effect.
According to this effect,the affinity of Hb for O2 decreases with decreasing pH.
However,blood is buffer so that the decrease in pH is very small with accumulation of CO2 in muscules.
The decreasing affinity of Hb for O2 with decreaing pH is shown in graph.
Bohr “s effect has important physiological effect in transporting O2 from the lungs to the respiring tissues &in transporting CO2
produced there back to lungs.
The CO2 produced diffuses from the muscles tissues to the capillaries & dissolved CO2
forms bicarbonate only very slowly.
Bohr”s effect showing oxygen binding curves of Mb & Hb
