1BIOCHEMISTRY 410Dr. Leisha MullinsWassily Kandinsky 1913What is Biochemistry? Why should you study it?• Biochemistry is the study of life on a molecular level• Biochemistry seeks to describe the structure, organization, and function of living organisms in molecular terms• In order to understand the life on the molecular level, you must first have a:– Knowledge of the chemical structures of the biological molecules– Understanding of the biological function of the molecules– Understanding of bioenergetics – the study of energy flow in cells23Biochemist are concerned with everything!Biochemist look at• The atomic level• The structural level• The cellular level• The role of the cell in the organism• Communication – Cell to cell– Biomolecule to biomolecule• Metabolic coordinationProperties of Biomolecules• Biological Macromolecules – have a directionality• Therefore they can be informational– 3D architecture • Weak Forces are Critical for Structure/Function – Van der Waals interactions– Hydrogen Bonds– Ionic Interactions– Hydrophobic Interactions4Look at table 1.3 for description5Water• Why is water important?• Water is the solvent for biological systems• Compounds are classified as to how they interact with water– Hydrophilic compounds interact (dissolve) with water– Hydrophobic compounds do not interact with water• Water has unusual properties– High boiling point, melting point, heat of vaporization, etc• H bonding is key to the properties of water– Solutes dissolved in water perturb its properties• Decrease freezing point or increase boiling point– The perturbations depend only on the number of solutes per unit volumeOsmotic Pressure• The high concentrations of dissolved solutes effectively decreases the concentration of water in cells compared to pure water• Pressure is required to prevent the influx of water into the cell – Plants and bacteria have strong rigid cell walls to contain the pressure– Mammalian cells are bathed in extracellular fluids of comparable osmolarity• Since the perturbations depend only on the number of dissolved molecules, osmotic pressure is minimized when cells store compounds in their polymeric form67Water is polar• Polar– Unequal sharing of electrons• Polarity is determined by the electronegativity of the atoms– Electronegativity – tendency to attract electronsElement ElectronegativityOxygen 3.5Nitrogen 3.0Sulfur 2.6Carbon 2.5Phosphorus 2.2Hydrogen 2.1Covalent Bond!!Proposed by Linus Pauling in 19328Dipole• Polar bonds and molecules are also known as dipoles• The atom with the greater electronegativity attracts the electrons giving that atom a partial negative charge• The remaining atom in the bond, therefore has a partial positive charge• Each atom of the bond has a different partial charge thus the term dipole9Hydrogen BondsHydrogen bonding is one of the most important interactions in biological molecules • Hydrogen bonding is an interaction between a covalently bonded hydrogen atom in a donor group and a pair of non-covalent electrons on an acceptor group• The ability of a group to act as a hydrogen bond donor depends on its electronegativityBond must be POLAR!10Common Hydrogen BondsNo C-H bonds!!C-H bonds are not Polar so NEVER participate in Hydrogen bondsBe able to identify: H bond donors and acceptors!11Solvent Properties of Water• Hydrophilic Compounds readily dissolve in water• Non-ionic polar– compounds dissolve in water because of the dipole–dipole interactions• Ionic compounds– readily dissolve in water because of the ionic –dipole interactions*Polar- Covalent bond partial charges*Ionic- Formal charge + or -12Hydrophobic Interactions• A non-polar substance does not readily dissolve in water• The H-bond network of water reorganizes to accommodate the non-polar solute. Hydrophobic groups aggregateAggregation causes less reorganization of the water13Amphipathic Molecules• Molecules that contain both polar and non-polar groups C=O14Non – covalent Bonds or ForcesNon-covalent bonds determine the complexity of molecular interactions within and between biomolecules• Non-covalent bonds are 10 –100 times weaker than covalent bonds• Single interactions are typically not sufficient to hold two species together• The 3-D structures of most macromolecules are determined as a result of the collective influence of the many weak individual interactions• Non-covalent bonds are reversible• Non-covalent interactions are specific• Size, shape and type of interaction all must be correct for