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 Ca2+ Mg2+ Fe2+ Cu2+ Zn2+ Co3+ Na+ K+ 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 The exothermic reaction is (hydrolysis): ATP + H2O → ADP + Pi + E ADP is adenosine diphosphate Pi is phosphate group, HOPO32- Reversible 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