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Cell Metabolism 2
Cell Metabolism Lecture 2- Water, Weak Bonds, and the Generation of Order
| Question | Answer |
|---|---|
| Key Concept about Life | Life functions on weak and reversible chemical bonds. Life occurs at 4 angstroms |
| Why Weak Bonds? | -Reversible -Formation of large stable structures -Energy concerns -Allow for fine tuning= large # of weak bonds as opposed to a small # of strong bonds |
| Importance of Weak Interactions | -Protein/substrate recognition -DNA structure -RNA structure -Protein structure -Membrane structure |
| Water | -medium of life -drives formation of macromolecules (hydrophilicity, hydrophobicity, achieving an energetic minimum) -water is a polar molecule, not a charged molecule |
| Brownian Motion | -thermal noise -the environment of a drop of water changes constantly -minuscule fluctuations (electrical charge, kinetic, diffusion) -bonds are formed and broken constantly |
| Key Concept about Water | the fact that water cannot dissolve everything is just as important as the fact that is can dissolve most things. Living things take advantage of the hydrophobic effect (compartmentalization) |
| Electrostatics | associations b/n +/- atoms or regions; electrons are not transferred; water's ability to dissolve (brownian motions/collisions; electrostatic interactions) -H2Os polar nature weakens ionic bonds -Added energy breaks the bonds -H20 stabilizes charged at |
| Hydrogen bond | -forms b/n 2 negative atoms each attempting to share a hydrogen -hydrogen's formal position is not known water will form up to 4 H-bonds when in bulk solvent -due to partial charges -water weakens H-bonds |
| Key Concept about the expulsion of water | the expulsion of water from a binding packet in a protein, or other site, is a key event in molecular recognition |
| Hydrophobic effect | -desire to expel water -affects entropy -affects enthalpy: E loss due to bond formation -goal is to lower E of system -hydrophobics are not attracted to each other, driven together by the elimination of water |
| Van der Waals | -asymmetry of electron cloud (occurs w/uncharged nonpolar molecules) -transient charged induce transient charges in nearby atoms (e- cloud displaces nearby e- cloud revealing the nucleus) -too close and a steric clash occurs |
| H+ Concentration | -critical value for cells to maintain -human blood: pH of 7.4 and a shift of 0.5 units can result in coma or death |
| Key Concept on the importance of H+ concentration | the effectiveness of weak bonds can change dramatically depending on the pH of the environment |
| Water doesn't always stay H20 | -ionization happens, but compared the amount of water the ionized products are very small -small amounts become hydronium (H3O+) and hydroxyl (OH-) |
| Km | means 1/1 of the maximum enzyme activity |
| pKa | means the pH at which the substrate is 1/2 protonated and 1/2 deprotonated -pH at which the acid is half dissociated |
| Keq | equilibrium constant= [H+][OH-]/[H2O] Concentration of products over reactants |
| Kw | -ion product of water -[H+]= 1x10^-7 -[OH-]= 1x10^-7 |
| pH | =log10(1/[H+])=-log10[H+] -as [H+] rises, [OH-] must decrease |
| Organics acids | -important biomolecules- aa, lactic acid, pyruvic acid -ionize to form the congugate base (-ate) |
| Henderson-Hasselbalch eq | pH=pKa+log([A-]/[HA]) |
| Buffers | acid/base conjugations resist changes in pH |
Created by:
clewis3
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