This document discusses the roles of metal ions in biology. Many metals act as active sites in enzymes, with iron, zinc and copper being especially important. Metals are classified as essential if required for life or nonessential. The s-block metals like sodium, potassium, magnesium and calcium help maintain electrical charges and osmotic pressure. The d-block metals serve as cofactors in many enzymes due to their ability to accept and donate electrons. Metal ions fulfill critical functions in processes like oxygen transport, bone formation, muscle contractions and more.

1. METAL IONS IN BIOLOGY

2. OBJECTIVES
To understand the role of metal ions in biology
To know something regarding the Na-K pump

3. CONTENTS
A Complex Life...
Classification
Metals in Biology
What Are Their Roles?
Ultra trace Elements
Conclusion

4. A COMPLEX LIFE…
Life’s a metal ion
Metals from s- and d- block acts as active sites in
majority of the enzymes
Fe , Zn and Cu
Metal-containing biomolecules-very much
important

5. CLASSIFICATION OF ELEMENTS

6. ESSENTIAL
NONESSENTIAL
ELEMENTS

7. ESSENTIAL ELEMENTS
• Required for the maintenance of life of plants &
animals
• Absence causes death or severe malfunction
NON ESSENTIAL ELEMENTS
• Don’t play any positive role in biological systems

9. TOXIC ELEMENTS
ELEMENTS AVERAGE
QTY (mg)
EXCESS OF QUANTITY
As 18 cancerous
Sn 6.0 cancerous
Bi 0.2 cancerous
Te 0.1 cancerous
Pb 121 Plumbism
Cd 5.0 High B.P.
Sb 8.0 Poisoning
Be 0.04 Causes heart disease
Cr (VI) 1.5 cancerous

10. Periodic Distribution of Biologically Important
Elements

11. METAL IONS IN BIOLOGY
Occur in several forms
Most advanced class- Metalloenzymes or
BIOLOGICAL CATALYSTS
Specific role
Major- d-block elements
But s-block elements are also important –
-Structural role (Ca)
-Enzymatic action(Mg)
-Homeostatic balance (Na & K)

13. WHAT ARE THEIR ROLES???

14. s-block metals
Bulk metals- K, Na, Mg and Ca
Maintain electrical charges
Osmotic pressure
Prevents the cells from collapsing by making it
turgid

15. Na+
Major cation of the extracellular fluid
Creates electrical potential for the functioning of
nerve cells & muscle cells
Na+ - 0.01 M
Na+ ions also serves as essential activating ions for
specific enzyme activity
Associated with acid-base balance

16. K+
 K – 0.15 M
 Electrolytic balance
 Proper functioning of heart
 Maintainenance of blood pressure
 Nerve impulses
 Aids in the waste removal process
 Enhances the muscle functioning
 In the synthesis of ribosomes

17. TRANSPORTATION OF IONS
• Charged Ions must pass through a Hydrophobic
Membrane
– Neutral gases (O2, CO2) and low charge density
ions (anions) can move directly through the
membrane
– High charge density cations require help

18. MECHANISMS
• Ionophores: special carrier molecules that wrap
around metal ions so they can pass through the
membrane by diffusion
• Ion Channels: large, membrane-spanning
molecule that form a hydrophilic path for
diffusion
• Ion Pumps: molecules using energy to transport
ions in one direction through a membrane

19. TYPES
• Passive Transport: moves ions down the concentration
gradient, requiring no energy source
– Ionophores and Ion Channels are Passive
• Active Transport: moves ions against the concentration
gradient, requiring energy from ATP hydrolysis
– Ion Pumps are Active
• Choice of Transport Mechanism
– Charge
– Size
– Ligand Preference

20. Sodium and Potassium Ion Pump
• Na+/K+-ATPase
– Membrane-Spanning Protein Ion Pump
– a2b2 tetrameric 294,000 dalton protein
– Conformational changes pump the ions: one
conformation binds Na+ best, the other binds K+ best
– Hydrolysis of ATP provides the energy for conformational
changes (30% of a mammal’s ATP is used in this reaction)
– Antiport transport: like charged ions are transported in
opposite directions
– Reversing the normal reaction can generate ATP
– Reaction can occur 100 time per second
– 3Na+in + 2Kout
+ + ATP4- + H2O 3Na+out + 2K+in + ADP3-
+ HPO4
2- + H+

21. Sodium and Potassium--Ionophore
• Nonactin: microbial Na+ and K+ ionophore
• Makes Na+ and K+ membrane soluble when complexed
• Oxygen Donors can be modeled by Crown Ethers
OOO
O
O O O
O
CH3
O
CH3
CH3
O CH3
CH3
O
CH3CH3
OCH3

22. Sodium and Potassium--Ion Channel
• Gramicidin: ion channel-forming molecule
– Helical peptide dimer
– Hydrophobic outer surface interacts with membrane
– Carbonyls and Nitrogens on inner surface can interact
with cations as they pass through
– Potassium selective: pore size and ligands select for K+
• Channels can be Voltage-Gated or activated by the
binding of a Chemical Effector which changes the
conformation
• 107-108 ion/second may pass (Emem = 100 mV)

24. Mg2+
Mg2+
- chlorophyll
- intracellular fluids
- carbohydrate metabolism
- enhances nerve impulses
(extracellular fluid)
- Active site of transferase,
phosphohydrase

25. Ca2+
-Bone formation
-- Brain functioning
-Maintains the heart rhythm
-- Blood clotting
-Formation of teeth enamel (fluoroapatite)
-1000 times less in intracellular fluids

27. d-block elements

28. VANADIUM
- extremely small amounts
- lichens & fungi have it in the active site of enzymes
- appears in nitrogenase, vanadium (v) in
haloperoxidases
CHROMIUM
Cr(III) – mammals
- lipid and glucose metabolism
- glucose tolerance
Cr(VI) & Cr(V) – mutagenic and carcinogenic, Cr(V)
damages DNA
- normal secretion of insulin

29. MANGANESE
- in wider range of organisms
- in important enzymes and
processes(photosynthesis)
- Mn (II) and Mn(III) have
redox role
Eg: In the enzyme superoxide
dismutase (SOD)

30. IRON
- Truly ubiquitous
- Required for tissue growth
- Responsible for oxygen transport
- In humans Hb & Mb represent 65% & 6% of all Fe in
body
- Ferritin- rapid access to Fe

31. SOMETHING ABOUT FERRITIN
• Structure:
– symmetric, spherical protein coat of 24 subunits
• Subunits are 175 amino acids, 18,500 daltons each
• Channels on 3-fold axes are hydrophilic: iron entry
• Inside surface is also hydrophilic
– Inner cavity
• 75 Å inner diameter holds 4500 iron atoms
• Iron stored as Ferrihydrate Phosphate
[(Fe(O)OH)8(FeOPO3H2) . nH2PO4]
– Iron-protein interface: binding of core to protein is
believed to be through oxy- or hydroxy- bridges

33. Pathway of Fe2+ from food stuffs to Hb and ferritin
involves the following mechanism

34. COBALT
- essential in small amounts
- cobalamines are found in many organisms (5 mg
in humans)
-enzymes with inert Co (III) has been discovered,
provides labile reaction sites
- extremely toxic to plants
NICKEL
- An important component in urease,
carbonmonoxide dehydrogenase and methyl-S-
coenzyme M reductase
- Exists in oxidation states like I , II, III

35. COPPER
- present at the active site of a large
number of enzymes
- 3rd most abundant transition element
- as electron transfer agents
Eg: cytochrome C oxidase , tyrosinase,
nitrite reductase
- blue copper proteins(type-1)
- in Hb formation

36. ZINC
- Adults 2-3 g
- carbonic anhydrase, carboxypeptidase
- 300 known enzymes
- DNA binding proteins
- zinc reserves
- Maintains normal concentration of Vit-A
- Tissue repairing & wound healing

38. Symptoms of Elemental Deficiency in Humans
__________________________________________________________
Ca Retarded skeletal growth
Mg Muscle cramps
Fe Anemia, immune disorders
Zn Stunted growth, skin damage, retarded maturation
Cu Liver disorders, secondary anemia
Mn Infertility, impaired skeletal growth
Mo Retarded cellular growth
Co Pernicious anemia
Ni Depressed growth, dermatitis
Cr Diabetes symptoms
Si Skeletal growth disorders
F Dental disorders
I Thyroid disorders
Se Cardiac muscular weakness
As Impaired growth (in animals)
________________________________________________________

39. ULTRATRACE ELEMENTS
Needed at less than 1 ppm or 50 ppb
Includes As, B, Si, Ni, V in humans
Other elements include Br, Cd , F , Pb , Li, Sn
Quite toxic at any concentration much above
concentrations ultra trace level

40. WHY CARBON INSTEAD OF SILICON?

41. CONCLUSION
Life evolved utilizing these elements that are
abundant & available to it and became
dependent upon them
Rare elements are not utilized….

42. REFERENCE
 Huheey J E, Keiter A Ellen, Keiter L Richard, Medhi K Okhil, “Inorganic
Chemistry-Principles of Structures and Reactivity”, 4th edition, Pearson
 Lawrance A Geoffrey, “Introduction to Coordination Chemistry”,2010,
Wiley
 Puri, Sharma and Kalia, “Principles of Inorganic Chemistry”,31st edition,
Milestone
 J D Lee, “Concise Inorganic Chemistry” , 5th edition, Wiley