Biochem - water

evan406's version from 2016-02-16 01:38


Question Answer
What is Entropy?a thermodynamic term used to designate that amount of energy in a system that is unavailable to do work.
What percentage of a cell is water?about 70%
What is the main solvent in cellular compounds?water
What kind of things does water dissolve?polar compounds and salts
What is an Amphipathic compounds?A compund that has both a hydrophobic and a hydrophilic component
What happens to Amphipathic compounds in water?They're forced to form micelles and bilayers
What is the function of micelles?micelles present the smallest hydrophobic area to the aqueous solvent.


Question Answer
3 steps in dissolving compounds in water?1. break water H-bonds
2. Break solute interactions
3. Make new water-solute interactions
What is the required for a spontaneous reaction?ΔG<0
Solubility in water depends on?The ability of a molecule to form hydrogen bonds with water
What is the basis of hydrophobic interactions?the inability to form hydrogen bonds with water
How does water dissolve polar compounds and how does it affect the entropy?-Water forms new hydrogen bonds with polar solutes able of forming hydrogen bonds.
-H-bonds are continuously broken and formed (no loss in entropy)
How does water hydrate salts and how does it affect the entropy?-Water interacts with charged solutes (ion-dipole interaction).
-Increase in entropy when crystalline substances dissolve
-H-bonds are continuously broken and formed (no loss in entropy)
What happens to nonpolar molecules in water solutions?-nonpolar molecules tend to aggregate in order to minimize the amount of surface exposed to water.
-This process is entropically driven rather than enthalpically


Question Answer
What happens to water molecules in the immediate vicinity of a non polar solute?-They are constrained in their possible orientations as they form a highly ordered cage-like shell around each solute molecule
-decrease in entropy for the water molecules
What are hydrophobic interactions?The forces that hold the non polar regions of the molecules
What affects the strength of hydrophobic interactions?results from the system’s achieving greatest thermodynamic stability by minimizing the number of ordered water molecules required to surround hydrophobic portions of the solute molecules.
What is the most important driving force for protein folding?Hydrophobic interaction is of great importance for the stabilization of the peptide and protein structure and seems to be the most important driving force for protein folding
Release of ordered water favors formation of what?an enzyme-substrate complex


Question Answer
What are the values for Keq, [H+], [OH-], [H2O]?Keq = 10-14
[H+] = 10-7
[OH-] = 10-7
[H2O] = 55.5
pH = ?-log [H+]
Henderson-Hasselbalch equation?pH = pKa + log [A-][HA]
What is the isoelectric point?pH = pKa
What is a buffer?-Buffers are aqueous systems that tend to resist changes in pH when small amount of acid (H+) or base (OH-) are added.
-A buffer system consists of a weak acid (the proton donor) and its conjugate base (the proton acceptor).
How does water affect ATP and/or polypeptides?-Formation/breakdown of ATP
-Synthesis/breakdown of polypeptides
What are the 4 Important interactions among biomolecules?1) Hydrogen bonds
2) Ionic interactions
3) Van der Waals (dipole-dipole, London-dispersion)
4) Hydrophobic interactions
What is effective concentration?-(AB)Ceff= Kintra /Kinter
-many interactions occur in close proximity, and are therefore, not totally independent thus an effective concentration is defined
What is the effect of water being slightly ionized?Water molecules have a slight tendency to undergo reversible ionization to yield a hydrogen ion (a proton) and a hydroxide ion,