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C9. Metal ions in biological systems

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C9.
Metal ions in biological systems
April 4th
General
• Many metal ions have role in biological
processes of the body
• The ions have different physical and
chemical properties
– Charge density
– Complex formation
– Oxidation states
• Minerals in food
The most important ions
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Ion
Ca2+
Mg2+
Fe2+
Cu2+
Zn2+
Co3+
Na+
K+
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Role:
1.5-2% of body mass, bones, teeth
Bones and teeth, intracellular activity
Hemoglobin, O2 transfer
Cofactor in enzymes
Cofactor in enzymes,growth, healing
In vitamin B12
Water balance, nerve impulses, fluids
inside and outside cells
ATP = adenosine triphosphate
• A nucleotide (ribose sugar, adenine base and
three phosphate groups)
• Energy currency of the cell, providing the energy
for most of the energy-consuming activities
• It regulates many biochemical pathways
ATP as energy source
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The exothermic reaction is (hydrolysis):
ATP + H2O в†’ ADP + Pi + E
ADP is adenosine diphosphate
Pi is phosphate group, HOPO32Reversible process
Na+/K+ pump
• Found in membranes of cells.
• Produces electrical and chemical gradient across
a cell membrane.
• It plays a very important role in nerve cell
membranes.
• Transmission of nerve impulses.
• Channel = tunnel-like trans membrane protein:
Na+-K+ ATPase
• K+ inside a cell
• Na+ outside a cell
• Cell surface membranes pump Na+ ions out of cell
and K+ in.
Na+/K+ pump
• The pump requires
energy:
• ATP + H2O → ADP +
Pi + E
• With 1 mol ATP:
• 3 mol of Na+ and 2
mol of K+ pumped
out/in
• Animation
Electron transport
• Energy from food is released through many
redox reactions (mitochondria)
• Transition metals have many oxidation
states.
• => They can carry charges.
• Cytochromes are oxidizing enzymes.
• Contain copper or iron as cofactors.
• Cu2+ + e– ↔ Cu+; Fe3+ + e– ↔ Fe2+
• Animation
Cu in cytochrome oxidase
Hemoglobin as oxygen carrier
• In each hemoglobin molecule there are
four heme groups
• Heme = Fe2+ surrounded by phorphyrin
group, four N act as ligands.
• As O2 carrier: O2 binds to Fe2+ as a ligand
• Reversible process
• CO and CN– bind irreversible to Fe2+
Hemoglobin
Binding of O2 alters the structure
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