2. INTRODUCTION
Bioinorganic chemistry is concerned with the roles of inorganic elements in
biological processes. Metal ions can have structural roles, catalytic roles, or
both.
30- 40 element use for biological process
Bulk Metal
Trace Element
2
3. BIOLOGICALLY IMPORTANT ELEMENTS
99% of human body is comprised of 11 elements:
Bulk biological elements: H, C, N, O, P, S, Cl
Bulk metal ion nutrients: Na, Mg, K, Ca
Essential elements for a wide range of bacteria/plants/animals
Transition metals: V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo
Non-Metals: (B), F, (Si), Se I, F.
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4. SOME OTHER FACTS
Mammals are believed to use only 25 of the known elements.
Eleven non-transition elements that make up 99.9% of the human
body (O, C, H, N, Ca, P, S, K, Cl, Na, Mg),
Three transition metals, Fe, Zn and Cu are needed in significant
amounts.
“Trace quantities” of many other transition elements are required to
maintain proper physical functioning.
Other elements in the human body (e.g. Rb, Zr, Sr, Al, Pb, Ba) are not
essential but incorporated inadvertently because they share chemical
and physical properties with essential elements.
Other elements are added to the list of elements thought to be essential
as our knowledge of the chemistry of living systems increases.
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5. SYMPTOMSOF ELEMENTALDEFICIENCYIN HUMANS
Sr. No. Metal Deficiency
1 Ca Retarded skeletal growth
2 Mg Muscle cramps
3 Fe Anaemia, immune disorders
4 Zn Stunted growth, skin damage, retarded
maturation
5 Cu Liver disorders, secondary anaemia
6 Mn Infertility, impaired skeletal growth
7 Mo Retarded cellular growth
8 Co Pernicious anemia
5
6. CONTINUE...
Sr No Metal Deficiency
9 Ni Depressed growth, dermatitis
10 Cr Diabetes symptoms
11 Si Skeletal growth disorders
12 F Dental disorders
13 I Thyroid disorders
14 Se Cardiac muscular weakness
15 As Impaired growth (in animals)
6
7. BIOLOGICALROLESOF METALLICELEMENTS
Structural
Skeletal roles via biomineralization
Ca2+, Mg2+, P, O, C, Si, S, F as anions, e.g. PO4
3, CO3
2.
Charge neutralization.
Mg2+, Ca2+ to offset charge on DNA - phosphate anions
Charge carriers: Na+, K+, Ca2+
Transmembrane concentration gradients ("ion-pumps and channels")
Trigger mechanisms in muscle contraction (Ca). Electrical impulses in nerves
(Na, K) Heart rhythm (K).
Hydrolytic Catalysts: Zn2+ , Mg2+
Lewis acid/Lewis base Catalytic roles. Small labile metals.
Redox Catalysts: Fe(II)/Fe(III)/Fe(IV), Cu(I)/Cu(II), Mn(II)/Mn(III)/(Mn(IV),
Mo(IV)/Mo(V)/Mo(VI), Co(I)/Co(II)/Co(III)
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8. BIOLOGICALROLES OF METALLICELEMENTS
Transition metals with multiple oxidation states facilitate electron transfer -
energy transfer. Biological ligands can stabilize metals in unusual
oxidation states and fine tune redox potentials.
Activators of small molecules.
Transport and storage of O2 (Fe, Cu)
Fixation of nitrogen (Mo, Fe, V)
Reduction of CO2 (Ni, Fe)
Organometallic Transformations.
Cobalamins, B12 coenzymes (Co), Aconitase (Fe-S)
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9. TRANSITIONMETALS IN BIOMOLECULES
Iron.
Most abundant metal in biology, used by all plants and animals including
bacteria. Some roles duplicated by other metals, while others are unique to
Fe. Iron use has survived the evolution of the O2 atmosphere on earth and
the instability of Fe(II) with respect to oxidation to Fe(III).
Zinc.
Relatively abundant metal. Major concentration in metallothionein (which
also serves as a reservoir for other metals, e.g. Cd, Cu, Hg). Many well
characterized Zn proteins, including redox proteins, hydrolases and nucleic
acid binding proteins.
Copper
Often participatse together with Fe in proteins or has equivalent redox roles
in same biological reactions. Reversible O2 binding, O2 activation, electron
transfer, O2
- dismutation (SOD).
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10. TRANSITIONMETALS IN BIOMOLECULES
Cobalt.
Unique biological role in cobalamin (B12-coenzymes) isomerization
reactions.
Manganese
Critical role in photosynthetic reaction centers, and SOD enzymes.
Molybdenum
Central role in nitrogenase enzymes catalyzing N2 NH3, NO3
NH3
Chromium, Vanadium and Nickel
Small quantities, uncertain biological roles. Sugar metabolism (Cr);
Ni only in plants and bacteria (role in CH4 production) and SOD
enzymes.
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12. CONTINUE…
Isomerases: B12 coenzymes (Co), Aconitase (Fe-S)
Oxygenases: Cytochrome P450 (Fe), Nitric Oxide
Synthases (Fe)
Electron carriers: Cytochromes (Fe)
Electron transferases Iron-sulfur (Fe)
Blue copper proteins (Cu)
Non Proteins
Transport Agents: Siderophores (Fe)
12
13. PORPHYRINS ANDRELATEDCOMPLEXESIN BIOINORGANICMOLECULES
• A porphyrin ring has a square planar geometry with a “pocket”
in the center.
• A metalloporphyrin complex can result by incorporating a
metal atom into the pocket Axial sites are available for other
ligands.
• Structure, specificity, and reactivity are changed by differing
the side chains, metal ions, and surrounding species.
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14. HAEMOGLOBINAND MYOGLOBIN
Oxygen transfer and storage agents in the blood and muscle
tissue.
Hemoglobin transports oxygen (O2) from the lungs/gills to
tissues and muscles.
Myoglobin stores oxygen (O2) in the muscles and tissues.
Oxygen commonly transfers from the hemoglobin to the
myoglobin for later use.
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15. HAEMOGLOBIN
Made up of four globin protein subunits ( and ).
Each protein partially encloses a heme group.
Each heme group is in a porphyrin pocket.
One axial position of the iron is bound to an imidazole nitrogen
from the protein.
One axial position is available/vacant or has H2O bound to it.
Dissolved O2 can bind reversibly to this axial position.
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18. COOPERATIVITY
• Cooperativity:
The function of hemoglobin is to bind O2 at high oxygen pressure and
carry it through the blood to needed areas (and myoglobin for storage).
Hb + 4O2 Hb(O2)4
Hb(O2)4 + 4Mb 4Mb(O2) + Hb
• As one iron binds an oxygen molecule in Hb, the molecular shape
changes to make binding of additional oxygen molecules easier. In a
similar fashion, initial removal of oxygen triggers the release of the
remaining oxygens.
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19. BOHR EFFECT & COMPARISION
At low partial pressures of O2,
Mb has a much greater affinity
for O2.
The Bohr effect.
Increased acidity favours the
release of O2 from Hb(O2)4.
]
O
][
Mb
[
)]
O
(
Mb
[
K
2
2
Mb
8
.
2
2
4
2
Hb
]
O
][
Hb
[
]
)
O
(
Hb
[
K
19
