Hemoglobin and insulin


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Hemoglobin and insulin

  1. 1. Hemoglobin and Insulin
  2. 2. Hemoglobin is composed of4 globin molecules.2 alpha globins2 beta globins4 Heme moleculesStructure of Hemoglobin2
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  4. 4. Molecular structure of the heme,with the iron in its center.a porphyrin ring, which contains 4 pyrrolemolecules cyclically linked together, and aniron ion ligand bound in the center4
  5. 5. Hemeproteins are a group of specialized proteins that containheme as a tightly bound prosthetic group.For example, the heme group of a cytochrome functions as anelectron carrier that is alternately oxidized and reduced.In contrast, the heme group of the enzyme catalase is part ofthe active site of the enzyme that catalyzes the breakdown ofhydrogen peroxide.hemoglobin and myoglobin, the two most abundant heme-proteins in humans, the heme group serves to reversibly bindoxygen.5
  6. 6. Structure of heme:Heme is a complex of protoporphyrin IX and ferrous iron.The iron is held in the center of the heme molecule bybonds to the four nitrogens of the porphyrin ring.The heme can form two additional bonds, one on eachside of the planar porphyrin ring.For example, in myoglobin and hemoglobin, one ofthese positions is coordinated to the side chain of ahistidine residue of the globin molecule, whereas theother position is available to bind oxygen.6
  7. 7. The alpha globin chain is composed of 141 amino acids& the beta globin chain is composed of 146 aminoacidsBoth alpha and beta proteins share similar secondaryand tertiary structuresHemoglobin Structure7
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  9. 9. Structure and function of hemoglobinHemoglobin is found exclusively in red blood cells,where its main function is to transport oxygen fromthe lungs to the capillaries of the tissues.Hemoglobin A, the major hemoglobin in adults, iscomposed of four polypeptide chains.Two alpha chains and two beta chains held together bynoncovalent interactions.9
  10. 10. Quaternary structure of hemoglobin:The hemoglobin tetramer can be envisioned as beingcomposed of two identical dimers (αβ)1 and (αβ)2 inwhich the numbers refer to dimers one and two.The two polypeptide chains within each dimer are heldtightly together, primarily by hydrophobic interactions.Hydrophobic amino acid residues are localized not onlyin the interior of the molecule, but also in a region onthe surface of each subunit.10
  11. 11. Interchain hydrophobic interactions form strongassociations between α-subunits and β subunits in thedimers.Ionic and hydrogen bonds also occur between themembers of the dimer.In contrast, the two dimers are able to move withrespect to each other, being held together primarily bypolar bonds.11
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  13. 13. Oxygen diffuses from alveolar air into the bloodbecause the venous blood has a lower partial pressure.The oxygen dissolves in the bloodSmall amount is carried as solution0.31-ml per 100-mlThe remainder of the oxygen is carried in chemicalcomposition with the hemoglobin in red blood cellsOxygen Transport13
  14. 14. Normal hemoglobins in adults14
  15. 15. Each globin chain (not hemoglobin) is controlled by a separategene.Genes are listed with the number inherited from each parent andthe chromosome on which they lie.There are two different gamma genes (and chains) that differ byone amino acid - a matter of little clinical significance.The gamma, delta and beta genes lie next to each other onchromosome 11.The two alpha genes lie next to each other on chromosome 16.15
  16. 16. Insulin is a hormone central regulating carbohydrateand fat metabolism in the body.Insulin causes liver cells, muscle cells and fat tissueto take up glucose from the blood and store it asglycogen in the liver and muscle.Insulin16
  17. 17. Insulin is producted by the pancreas, which has twoimportant functions :1. Producing hormones – insulin and glucagon whichregulate blood sugar levels.2. Producing pancreatic digestive enzymes.Insulin is released when any of the several stimuli aredetected– stimuli include ingested protein andglucose in the blood from digested food.Production of insulin17
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  19. 19. Insulin is a peptide hormone composed of 51 aminoacids and has a molecular weight of 5808 Da.Insulin structure19
  20. 20. Insulin is produced and stored in the body as ahexamer , while the active form is the monomer.20
  21. 21. Mature insulin consists of the 21 amino acids in A chainand 30 amino acids in B chain linked by disulfide bonds.21
  22. 22. Structure of InsulinInsulin is synthesized as a preprohormone22
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  24. 24. Insulin Molecule24
  25. 25. Control of the cellural intake of certain substances.Increase of DNA replication and protein sythesis.Modification of the activity of numerous enzymes.Actions of insulinon the human metabolism25
  26. 26. It stimulates synthesis of glycogen, fat, and protein.It inhibits breakdown of glycogen, fat, and protein.It increases glucose transport into cells.It is the main hormone that controls the blood glucoselevel.Actions of insulinon the human metabolism26
  27. 27. Insulin is being produced biosynthetically usingrecombinant DNA technology. More recently,reserchers have succeded in introducing the humaninsulin gene into plants and in producing insulin inthem. This technique is set to reduce productioncosts.Before it was possible to produce insulinbiosynthetically it wa aquired from animals andpurified so it could be used as injections.Insulin for medical purposes27
  28. 28. Protein DenaturationIt results in the unfolding and disorganization of theproteins secondary and tertiary structures, which arenot accompanied by hydrolysis of peptide bonds.Denaturing agents include:heat,organic solvents,mechanical mixing,strong acids or bases,detergents,and ions of heavy metals such as lead and mercury.28
  29. 29. Denaturation may, under ideal conditions, be reversible,in which case the protein refolds into its original nativestructure when the denaturing agent is removed.However, most proteins, once denatured, remainpermanently disordered.Denatured proteins are often insoluble and, therefore,precipitate from solution.29
  30. 30. 30THANKS