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26 Cards in this Set
- Front
- Back
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What is a hydrogen bond?
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an electrostatic attration an electronegative molecule and an electropositive hydrogen.
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Hydrogen bonds are stronger/weaker than covalent bonds?
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weaker (20 kJ/mol vs. 348 kJ/mol)
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What is the hydrogen bond acceptor?
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The electronegative atom participating in the bond
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What is the hydrogen bond donor?
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The electropositive hydrogen
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Why does butanol have a very high boiling point compared to butane?
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Because hydrocarbon H's do not participate in H-bonds
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What types of compounds form H-bonds w/H20 and tend to be water soluble?
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alcohols, ketones, and compounds w/N-H bonds (uncharged, polar molecules)
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In what orientation are H-bonds strongest?
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When the H-bond acceptor is "in-line" with the covalent bond of the H-bond donor (H)
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What are electrostatic interactions?
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a property of charged particles
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What do most charged groups arise from in biological molecules?
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derivates of carboxylic acids (COO-) amines (-NH3+), phosporic acid, and sulfuric acid
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What do alternative bonding partners do to ionic interactions?
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Weaken them
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What is a salt bridge?
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The association of two ionic protein groups of opposite charge
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Give an example
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carboxyl group of Glu
ammonium group of Lys |
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Free ions in aqeous solution are highly _______?
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solvated
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What is the result of this?
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There is no difference in free energy between the ionic and solvated form.
Thus, they contribute little to the stability of the protein |
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Why do polar molecules dissolve readily in H20?
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Because they can replace water-water interactions with water-solute interactions (move favorable)
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CO2, N2, 02, are polar/nonpolar?
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non-polar
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What is a hydrophobic interaction?
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The forces that cause non-polar molecules to minimize contact w/polar solvents
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Why is water effective at screening electrostatic interactions between molecules?
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Because of it's high di-electric constant (E) - # of dipoles present in a solvent
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What formula gives the strength of the ionic interaction btw. molecules?
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F=(Q1*Q2)/Er^2
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Hydrophobic solutes in a polar solvent cause a _____ in enthalpy and _____ in entropy
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small increase in enthalpy
decrease in entropy |
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Why is the decrease in entropy present?
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because water molecules must form a cage-like shell around the non-polar solute, decreasing the number of highly ordered H20 molecules
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What is a micelle?
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an amphipathic molecule in solution (polar faces out, non-polar away from H20)
ex. of hydrophobic interaction |
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What is the driving force behind a substrate binding to enzyme in a polar solvent
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The increase in enthalpy caused by disrupting the structures around the substrate and enzyme
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What are the 3 types of Van der Waals interactions?
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1.dipole-dipole
2.dipole-induced dipole 3.induced dipole-induced dipole |
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What is the Van der Waals radius
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a measure of how close 2 atoms can approach each other (measure of maximum attrative force)
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What is referred to as Van der Waals contact
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1. When the attractive forces balance repulsive force
2. Equal to Van der Waals radius |
