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Lecture 2
water, pH, buffers and membranes
| Question | Answer |
|---|---|
| significance of water | -where most proteins work - abundant molecule in cell ~60-90% - transport of nutrients, enzymes catalyzed rxns of metabolism and transfer of chem energy happens there - polar. interact w other molecules of h2o and non h2o -solvent/reactant |
| Because water is polar, it can form H-bonds with other water molecules in a | tetrahedral array |
| H bonds | very weak, non-covalent bonds, hydrogen and N O or S |
| describe the amount of H bonds in the three states of water | - Solid, every possible H bond - liquid, 20-30% H bonds - Gas, 0% H bonds. Covalent bonds still intact |
| List 4 properties of water | 1. High boiling and melting pts 2. surface tension- waters cant interact "up"=sideways interactions 3. H bonds cause ice to be less dense than liquid water and float 4. high specific heat 5. high heat of vaporization |
| specific heat vs heat of vaporization | specific heat- heat/energy needed to raise temp of 1g of water 1C heat of vaporization- amount of heat needed to cause a change to gas |
| how does water dissolve ionic and polar molecules? | - part of water interacts with + part and +part of water interacts with - part of molecule |
| uncharged polar substances ___________ dissolve in water | can |
| hydrophobic effect | weak noncovalent interaction where hydrophobic molecules to come together and aggregate when put in water to reduce surface area |
| what noncovalent bonds/interactions are there? briefly explain each | 1. charge-charge (electrostatic) interactions: ion-ion(A+B-), ion-dipole(Na+Cl- in water), dipole-dipole (2 polar molecules) 2. hydrophobic interactions- nonpolars aggregating 3. Van der Waals- close enough, bond 4. Hydrogen bonds- H with N O or S |
| why are weak noncovalent interactions important? | additive force in the structure and folding of molecules. They are integral to normal functioning of the body as well as diseases |
| where do Van der Waals work? | in all molecules, they operate at an optimal distance. As atoms move closer together, energy will rise due to electron-electron repulsion |
| nonpolar noncharged biomolecules interact with eachother by | electrostatic forces |
| what makes covalent bonds stronger than non-covalent? | the sharing of electrons |
| Non polar interactions are ___________ in an aqueous environment and ___________________ in a non polar environment | strengthened, weakened |
| polar interactions are ___________ in an aqueous environment and ___________________ in a non polar environment | weakened, strengthened |
| why does water tend to ionize? | H+ and OH- ions have a short lifetime |
| equilibrium constant of wate r | keq=([H+][OH-])/[H2O]=Kw=1x10^-14 |
| pure water is neutral meaning it has equal number of H+ and OH- ions which is | 1x10^-7 |
| pH/pOH formula | pH= -log[H+] pOH= -log[OH-] both added should equal 14 |
| equilibrium constant for the dissociation of a proton from an acid in water is called | acid dissociation constant Ka=([H+][A-])/[HA] |
| can be used to talk about the change in degree of ionization of an acid | pKa=-logKa |
| mixture of weak acid and conjugate base of that acid that resists changes in pH | buffer |
| practical buffering zone | pKa + or - 1pH |
| henderson hasselbalch equation | pH=pKa+log ([A-]/[HA]) |
| buffers work best at | pH which they are 50% dissociated |
| what changes blood pH from normal? | metabolism, it produces ~20 moles of acid per day (as CO2, lactate, "ketone bodies") |
| how does the body get rid of excess acid? | exhaling CO2 (lungs, fast) excreting H+ (kidneys, slow) NH4+ |
| not being able to rid the blood of excess H+ can lead to | acidosis |
| how is acidosis life threatening | - affects protein structure - affects molecular interactions essential to life (depend on pH) |
| how can pH affect biological processes? | molecular interactions depend on pH which affects molecular charge 1. enzyme-substrate (inactive enzyme) 2. receptor-ligand 3. Hb+O2 <--> Hb[O2]4+3H+ low pH increases Hb release of O2 by mass action 4. transmembrane pH gradient affects Na+ gradient |
| explain how the bicarbonate buffer system of the blood works | 1. hydration of CO2 catalyzed by carbonic anhydrase to produce H2CO3 (unstable) 2. rapid, nonenzymatic dissociation of H2CO3 to H+ and HCO3- which act as buffer system in RBCs. Free protons affect O2 binding affinity |
| what lowers blood pH? how does body respond? | CO2 as a byproduct of oxidative metabolism increasing rate of breathing to expel CO2 raising blood pH again |
| normal pH of blood? | 7.35–7.45 |
| how does blood always stay prepared for a stressor that lowers pH? | by having a bicarbonate that is normally about 20x that of CO2 in the blood. |
| pka of carbonic acid | 6.1 |
| how to find blood pH? | pH=6.1+log ([HCO3-]/[pCO2x 0.03]) |
Created by:
rusulali97
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