3-chemical foundations-22-07-2024.ppt

Chemical and genetic foundations T. Kalaivani  Genetic foundations Genetic information is encoded in the linear sequence of 4 deoxy ribonucleotides in DNA Double- helical DNA molecule contains an internal template for its own replication and repair Linear sequence of ami...

Chemical and genetic foundations T. Kalaivani  Genetic foundations Genetic information is encoded in the linear sequence of 4 deoxy ribonucleotides in DNA Double- helical DNA molecule contains an internal template for its own replication and repair Linear sequence of aminoacids in a protein , which is encoded in the DNA of the gene produces a protein’s unique 3D structure Individual macromolecules with specific affinity for other macro molecules self- assemble into supramolecular complexes 1.4 Genetic Foundations Genetic continuity is vested in single DNA molecules The structure of DNA allows for its replication and repair with near-perfect fidelity Complementarity between the two strands of DNA 1.4 Genetic Foundations The linear sequence in DNA encodes proteins with three-dimensional structures DNA to RNA to protein to enzyme (hexokinase) Chemical foundations  Chemical foundations Biomolecules are compound of carbon with a variety of functional groups Cells contain a universal set of small molecules (metabolites of major pathways and secondary metabolites in plants) Cells contain macromolecules 3 D Structure is described by configuration and conformation Interactions between biomolecules are stereospecific Elements found in living organisms Chemical foundations The first tier element are all able to form covalent bonds! 1.2 Chemical Foundations Elements essential to animal life and health. Bulk elements (shaded orange) are structural components of cells and tissues and are required in the diet in gram quantities daily. For trace elements (shaded bright yellow), the requirements are much smaller: for humans, a few milligrams per day of Fe, Cu, and Zn, even less of the others. The elemental requirements for plants and microorganisms are similar to those shown here; the ways in which they acquire these elements vary.  Carbon is extremely versatile in forming covalent bonds with other atoms or itself Carbon accounts for more than half of the dry weight of cells. Forms single bond with H atoms , both single and double bonds with nitrogen and oxygen Forms C-C single bonds (stable and greatest significance in biology) but also can form C=C and C triple bond C Tetrahedron arrangement of carbon with an angle of 109.5 between two bonds and bond length 0.154nm. (c-c single bond) double bond is shorter (0.134nm) C-C- single bond- free rotation is possible C=C- Rigid and allows little rotation. 1.2 Chemical Foundations Biomolecules are compounds of carbon with a variety of functional groups Geometry of carbon bonding  Bonding versatility of carbon plays a major role in evolution Covalently linked carbon atoms can form linear chains, branched chains and cyclic structures All kinds of functional groups (e.g., alcohol, amino, carboxyl) can be attached to the hydrocarbon backbones (thus making the major biomolecules like proteins, nucleic acids, carbohydrates, lipids and etc.).  Versatility of carbon bonding: Carbon is able to form covalent bonds with An H, enormous O, N and diversity itself. of life molecules can thus be made.  Functional groups H O found in biomolecules N P S tiple functional groups are usually found in one biomolecule. ucture of Acetyl-coenzyme A (Acetyl-CoA) 1.2 Chemical Foundations Macromolecules are the major constituents of cells Macromolecules : polymers with M.W. above ~5000 that are assembled from relatively simple precursors. protein, nucleic acid, Polysaccharide, etc. Oligomers  A carbon-based biomolecule may have stereoisomers of different configuration or Two compounds having the same formula conformation can have different spatial arrangements in covalent bond linkages, i.e., having different configurations -fixed spatial arrangements of atoms. A biomolecule can have counterless or limited three dimensional structures, i.e., having different conformations , due to the rotating feature of C-C bonds (with the same covalent linkages). Configuration may result from the presence of a C=C bond Each is a well-defined compound with unique chemical properties and distinct biological roles. They are geometric isomers (i.e., 2-dimensional) Much input of energy is needed for their interconversion (via breakage/formation of covalent bonds. （ he two are enantiomers The two are the same Configuration may also result from t presence of asymmetric carbons. symmetric (chiral) carbon, linking to four diffe tituents, can have two configurations, produc a pair of stereoisomers called enantiomers. 1.2 Chemical Foundations Three-dimensional structure is described by configuration and conformation Molecular configuration can be changed only by breaking covalent bonds. For a carbon atom with four different substituents (a chiral carbon), the substituent groups can be arranged in two different ways, generating stereoisomers with distinct properties. Only one stereoisomer is biologically active. Molecular conformation is the position of atoms in space that can be changed by rotation about single bonds, without breaking 1.2 Chemical Foundations Three-dimensional structure is described by configuration and conformation Chiral center Greek chiros “hand” 1.2 Chemical Foundations Three-dimensional structure is described by configuration and conformation Two types of stereoisomers Interactions between biomolecules are stereospecific  Boat and chair conformation of glucose  Interactions between biomolecules are usually stereospecific For biomolecules having an asymmetric carbon, usually only one of the two enantiomers will be produced and used by the cell( Example D-Sugars and L- aminoacids), as a result of the asymmetry of the enzymes catalyzing such transformations. Examples : Interaction of reactant with enzyme, hormone with its receptor on a cells surface and antigen with its specific antibody.