tailieunhanh - Lecture Principles of biochemistry - Chapter 2: Water

In this chapter, you will learn: Know why water is polar, understand how water forms H-bonds, understand how H-bonds stabilize the structure of water, understand how water dissolves polar and ionic compounds, understand how water interacts with non-polar compounds, know what is a solvation/hydration shell,. | Chapter 2: Water WHY DO WE NEED TO DO THIS AGAIN!!! Very polar Oxygen is highly electronegative H-bond donor and acceptor High ., ., heat of vaporization, surface tension Properties of water Water dissolves polar compounds solvation shell or hydration shell Non-polar substances are insoluble in water Many lipids are amphipathic How detergents work? Hydrogen Bonding of Water Crystal lattice of ice One H2O molecule can associate with 4 other H20 molecules Ice: 4 H-bonds per water molecule Water: H-bonds per water molecule Biological Hydrogen Bonds non-covalent interactions Relative Bond Strengths Bond type kJ/mole H3C-CH3 88 H-H 104 Ionic 40 to 200 H-bond 2 - 20 Hydrophobic interaction 3 -10 van der Waals - 4 Ionization of Water Ionization of Water H20 + H20 H3O+ + OH- Keq= [H+] [OH-] [H2O] H20 H+ + OH- Keq= X 10-16M [H2O] = M [H2O] Keq = [H+] [OH-] ( X 10-16M)( M ) = [H+] [OH-] X 10-14 M2 = [H+] [OH-] = Kw If [H+]=[OH-] then [H+] = X 10-7 pH Scale Devised by Sorenson (1902) [H+] can range from 1M and 1 X 10-14M using a log scale simplifies notation pH = -log [H+] Neutral pH = Weak Acids and Bases Equilibria Strong acids / bases – disassociate completely Weak acids / bases – disassociate only partially Enzyme activity sensitive to pH weak acid/bases play important role in protein structure/function Acid/conjugate base pairs HA + H2O A- + H3O+ HA A- + H+ HA = acid ( donates H+)(Bronstad Acid) A- = Conjugate base (accepts H+)(Bronstad Base) Ka = [H+][A-] [HA] Ka & pKa value describe tendency to loose H+ large Ka = stronger acid small Ka = weaker acid pKa = - log Ka pKa values determined by titration Phosphate has three ionizable H+ and three pKas Buffers Buffers are aqueous systems that resist changes in pH when small amounts of a strong acid or base are added. A buffered system consist of a weak acid and its conjugate base. The most effective buffering occurs at the region of minimum slope on a titration curve (. around the pKa). Buffers are effective at pHs that are within +/-1 pH unit of the pKa Henderson-Hasselbach Equation 1) Ka = [H+][A-] [HA] 2) [H+] = Ka [HA] [A-] 3) -log[H+] = -log Ka -log [HA] [A-] 4) -log[H+] = -log Ka +log [A-] [HA] 5) pH = pKa +log [A-] [HA] HA = weak acid A- = Conjugate base * H-H equation describes the relationship between pH, pKa and buffer concentration Case where 10% acetate ion 90% acetic acid pH = pKa + log10 [ ] ¯¯¯¯¯¯¯¯¯¯ [] pH = + () pH = pH = pKa + log10 [ ] ¯¯¯¯¯¯¯¯¯¯ [] pH = + 0 pH = = pKa Case where 50% acetate ion 50% acetic acid pH = pKa + log10 [ ] ¯¯¯¯¯¯¯¯¯¯ [] pH = + pH = Case where 90% acetate ion 10% acetic acid pH = pKa + log10 [ ] ¯¯¯¯¯¯¯¯¯¯ [] pH = + pH = pH = pKa + log10 [ ] ¯¯¯¯¯¯¯¯¯ [] pH = - pH = Cases when buffering fails

• Sinh học
• Principles of biochemistry
• Lecture Principles of biochemistry
• Biological systems
• Biochemical compounds
• Properties of water
• Hydrogen bonding
• Ebook Principles of biochemistry
• Principles of biochemistry (4th edition)
• The glyoxylate cycle
• Fatty acid catabolism
• Electron Transfer reactions
• Evolutionary foundations
• Protein interactions modulated
• Nucleic acid structure
• Biological macromolecules
• Chemical principles
• Amino acids
• Amino acid structure
• Protein purification
• Cell extract
• Protein classification
• Protein 3 Dimensional structure
• Protein folding
• Protein 3 D structure
• 3 D structure
• Oxygen binding curve
• Enzyme kinetics
• Rate constants
• Catalytic Power
• Classes of enzymes
• Inhibitor kinetics
• Enzyme regulation
• Allosteric regulation
• Enzyme action
• Mechanisms of enzyme action
• Ions Cofactors
• Metal ion
• Nguyên lý hóa sinh
• Biotin cofactor
• Conformation of monosaccharides
• Carbohydrate classifications
• Oligo carbohydrate
• Polysaccharides carbohydrate
• Lipid subclasses
• Acyl lipids
• Fluid mosaic model
• membrane transporters
• Metabolism proceed
• Anaeorbic process
• Triose Phosphate Isomerase
• Regulation of glycolysis
• Control points in glycolysis
• Citric acid cycle
• TCA cycle