Bioinorganic Chemistry: Metals' Roles, Deficiencies, and Toxicity in CHEM-332, Study notes of Inorganic Chemistry

Download Bioinorganic Chemistry: Metals' Roles, Deficiencies, and Toxicity in CHEM-332 and more Study notes Inorganic Chemistry in PDF only on Docsity! 0 1 Bioinorganic Chemistry Essential Metals, Deficiencies and Toxicity CHEM-332 0 1 Bioinorganic Chemistry CHEM-332 Metals although they constitute a fraction of the mass of living organisms, they play key roles in practically all the biological processes that keep living cells alive. •DNA replication essential for cell reproduction needs the element calcium. •Iron is needed to transport oxygen thought the human body. •Nickel although its exact chemical role is not well understood, is essential to all vertebrates. 0 1 Bioinorganic Chemistry Key Concept Occurrence of metals in biological systems is widespread. The roles of the metals in biomolecules fall into two classes: Active: where they are right at the active center of the biomolecule and they are involved directly on the chemical processes. Passive: where the metal plays a structural role and they affect the conformation of the biomolecule, but the metal is not directly involved in the chemical processes. RR-M 1.1 0 1 Bioinorganic Chemistry Key Concept Metal centers include: Atomic ions in aqueous solution. Coordination complexes (metal + ligand) Organometallic compounds (metal-carbon bonds) Metallic Clusters (metal-metal bonds) RR-M 1.1 0 1 Key concept Chemical activity depends on: Possible ionic states of the metals Equilibria between metals and their ligands which depend on thermodynamic factors Kinetics of the metal-ligand systems Electron transfer processes, lead to oxidation, reduction processes. RR-M 1.1 Bioinorganic Chemistry 0 1 Essential Elements Macro: Atomic Ions (Na+, K+, Mg2+, Ca2+, Cl- ) Molecular Ions (PO43-, SO42-) Note there are metals and non-metals at the macro level. RR-M 1.2 0 1 Essential Elements Trace: Covalent (Fe, Zn, Cu) Atomic ions (Zn2+) Multivalent atomic ions (Fe2+, Fe3+, Fe4+, Cu+,Cu2+,Cu3+) Note there are only metals at the trace level. RR-M 1.2 0 1 Essential Elements Ultra-trace: Covalent non-metals (F, I, Se, Si) Covalent metals (Mn, Mo, Co, Cr, V, Ni, Sn) Non-metal Atomic ions (F-, I- , Se2-, Si4+) Metallic Monovalent ions (Cd2+, Pb2+, Li+) Note the multivalent atomic ions [Mn(II, III, IV), Mo(IV,V,VI), Co(II,III), Cr(III,VI), V(III,IV), Ni(I, II, III), Sn(II,IV)] RR-M 1.2 0 1 Dose-Response Curve RR-M 1.2 Health Disease Essentiality Severe Possible Healthy Possible Severe Deficiency Deficiency State Excess Toxicity Zone of Conflict Zone of Conflict Death Intake Zone of Decreasing Health Zone of Decreasing Health Zone of Health Excess Health Disease Death Zone of Decreasing Health Deficiency JCV 0 1 Examples of Metal Functions Metals in living organisms have many functions such as: Charge Carriers. Metals are involved in charge maintenance, osmotic balance, & nerve impulses. Structural Elements. Metals influence protein structure, they can act as protein activity triggers. Electron Transfer. Metals are central to the enzymatic processes, like in nitrogen fixation. Dioxygen Transfer. Metals bind and carry molecular oxygen, like in hemocyanin, myoglobin RR-M 1.3 0 1 Metal Functions: Groups I & II Group I and Group II metals usually operate: in the maintenance of osmotic balance in the electric potential across cell membrane maintenance of s. as structural elements in the conformation and folding of protein chains. RR-M 1.3 0 1 Metal Functions In general, the possible functions of metals depend on: their location, distribution and ease of transport within the living organism. affinity for protein binding. Metals usually bind to the lone pairs in N, O or S atoms present within proteins. the number of possible stable/stabilized oxidation states the metal can exhibit. RR-M 1.3 0 1 Essential Metals Main Group Metals Macro: Na, K, Mg and Ca Transition Metals Trace: Fe, Cu, Zn Ultra-trace: V, Cr, Mn, Co, Ni, Zn, Mo, Sn, Pb and Cd. where the metals in red are the multivalent elements. IB 9.II 0 1 Deficiencies and Toxicity of Metals IB 9.II 0 1 Iron Toxicity Iron toxicity can be caused by: Ingestion of excessive amount of iron pill supplements Cooking and storing acidic foods in iron containers. Treatment Removal of iron by chelating compounds such as the siderophore desferrioxamine, a naturally occurring polypeptide, with a great specific affinity to iron(III). IB 9.III 0 1 Zinc in the Body The average human adult has about 2 g of zinc. 15 mg to 20 mg daily intake are needed. The understanding of the roles of zinc in the human body are not able to explain all the observed effects associated with zinc deficiency. Most of the zinc in the skin and bones. IB 9.II 0 1 Zinc Defficienacy It is not a very common event An unbalanced diet can lead to Zn deficiency Certain foods can prevent zinc absorption. It can lead to growth retardation, testicular atrophy, skin lesions, loss of appetite, and loss of body hair. It affects the enzyme activities of:  alkaline phosphatase (removes phosphate groups), carboxypeptidase (cleaves peptide bonds, on the C-end of proteins), thymidine kinase (involved in DNA synthesis) IB 9.II 0 1 Copper Deficiency It can occur because of lack of it in the diet or because of a diet that prevents copper from being absorbed. It can lead to: brain disease in infants. anemia, since copper is needed in the productions of red blood cells. heart disease. IB 9.II 0 1 Copper Toxicity It leads to: Liver disease Neurological damage Green or brown rings around the cornea Wilson’s disease is a genetic metabolic syndrome where people with this genetic defect cannot tolerate the normal amount of copper in the body and exhibit copper toxicity symptoms. IB 9.III 0 1 Copper Toxicity “Chelate Treatment” of patients with chelating agents such as CaNa2(EDTA) can effectively reduce the amount of copper. However it also reduces the amounts of other metals which are also chelated as EDTA enter into the human body. EDTA chelated metals are readily processed by the liver and eliminated through the kidneys. Patients undergoing EDTA treatment for copper are given doses of the other metals to compensate for their loss from the “Chelate Treatment”. IB 9.III