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Metals
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bulk eliments trace eliments for some species Periodic Table
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Metals essential for life: The role for most is uncertain Na, K, Mg, Ca V, Cr, Mn, Fe Co, Ni, Cu, Zn Mo, W
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General roles of metal ions in biology Na, K: Na, K:Charge carriers Osmotic and electrochemical gradients Nerve function Mg, Ca: Mg, Ca:Enzyme activators Structure promoters Lewis acids Mg 2+ : chlorophyll, photosynthesis Ca 2+ : insoluble phosphates
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Other metal ions: less well defined and more obscure roles Zn: Zn: Metalloenzymes Structure promoters Lewis acid Not a redox catalyst! Fe, Cu, Mo: Fe, Cu, Mo: Electron-transfer Redox proteins and enzymes Oxygen carrying proteins Nitrogen fixation
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Biochemical Reactivity Promotion of Appropriate Geometry Change acid/base character Change Redox potentials Change ionic concentration Formation of Unique species Formation of structural materials Activation of small molecules (NO)
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Zinc and Copper Zinc is found in more than 80 different enzymes. Carboxypeptidase Catalyzes hydrolysis of peptide bonds Carbonic anhydrase CO 2 HCO 3 - Copper Ceruloplasmin – blue-glycoprotein Iron storage and oxidation/reduction Superoxide dismutase Conversion of superoxide to peroxide to water. Also Lactase, ascorbate oxidase and plastocyanin
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Alkali metals Terrestrial distribution: LiNaKRbCsFr 0.060 nm0.133 nmionic radii 0.095 nm Distribution in vivo: (Li)NaK(Rb)
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Element% of total number of atoms in human body Number of grams in a 70-kg Man H636580 O 25.548550 C 9.512590 N 1.41815 Ca 0.311700 P 0.22680 K 0.06250 S 0.05100 Cl 0.03115 Na 0.0370 Mg 0.0142 Fe < 0.017 Mn, Co, Cu, Zn, Mo, V, Cr, Ni, F, < 0.011 Si, Se, As
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Role: Na + Extracellular fluid Osmotic balance „sodium pump” Acid-base balance Conformation of proteins nucleic acids Electrical impulse of nerve system Mg 2+ 3Na + ic + 2K + ec + ATP 4- + H 2 O 3Na + ec + 2K + ic + ADP 3- + HPO 4 2- + H +
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K+K+ Enzyme activator Conformation of proteins RNA (replication) Secretion of gastric acid Transmembrane potentials! Complexes of alkali metals (Na +, K + ) Cyclic antibiotics Valinomycin Monactin Nonactin polyetherssynthetic cryptands
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18-Crown-618-Crown-6 negative charge concentrated in cavity inside the molecule O OO O O O
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18-Crown-618-Crown-6 O OO O O O
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18-Crown-618-Crown-6 forms stable Lewis acid/Lewis base complex with K + O OO O O O K+K+
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18-Crown-618-Crown-6 O OO O O O K+K+
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Alkaline Earth Metals Terrestrial distribution: Be MgCaSrBaRa Distribution in vivo: MgCa Be, Ba TOXIC! Sr (not particularly toxic) 90 Sr accumulates in bones
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Element% of total number of atoms in human body Number of grams in a 70-kg Man H636580 O 25.548550 C 9.512590 N 1.41815 Ca 0.311700 P 0.22680 K 0.06250 S 0.05100 Cl 0.03115 Na 0.0370 Mg 0.0142 Fe < 0.017 Mn, Co, Cu, Zn, Mo, V, Cr, Ni, F, < 0.011 Si, Se, As
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Mg 2+ Plants chlorosis CHLOROPHYLL nervous system (tetany) active transport (intracellular) enzyme activator (e.g. ATP-ase) Ca 2+ antagonist Ca 2+ Inhibits Mg 2+- activated enzymes Extracellular: clotting (10 -3 M) Ca 2+ prothrombin thrombin-fibrinogen-fibrin Alkaline Earth Metals
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Chlorophyll
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The interactions between ATP, Mg 2+, and arginine and lysine residues at the active site of an enzyme Since all the negative charges in ATP are neutralized, ATP is readily approached by nucleophiles
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- plasma proteins bones (hydroxyapatite) Ca 5 (PO 4 ) 3 (OH) - intracellular: enzymes 10 -8 mol/dm 3 - muscle contraction: troponin - Calcium triggering: calmodulins (Ca-binding proteins) largely helical and undergo helix/helix motion Ca-binding hands: a short two-strand unit -sheet
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Ca 2+ signal metabolic controls N T P Protein phosphatasec-NMP protein DNA New signals
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