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What are waters active roles in biological systems?
Water is a participant in many biochemical reactions
What are waters passive roles in biological systems?
The structures of biomolecules (proteins, membranes, nucleic acids) are in response to their interaction with water
Why is water a dipole?
- O has partial (–) charge
- H has partial (+) charge
- -Electrostatic interaction between an electronegative atom and a hydrogen linked to a second electronegative atom (oxygen, nitrogen, flourine)
- -1/25 the strength and double the length of a covalent bond
- -Stronger when the electronegative atom is aligned with the hydroxyl than at an angle
How many Hydrogen Bonds can a water molecule make?
- -Water can donate two hydrogen bonds and accept two hydrogen bonds.
What contributes to waters high heat of vaporization and high specific heat capacity?
The large number of hydrogen bonds
What are Amphipathic molecules?
- molecules that have hydrophobic chains and ionic or polar
What is the Hydrophobic effect
the exclusion of nonpolar substances by water (critical for protein folding and membrane formation)
What types of molecules are most soluble in water?
molecules that are ionic, polar(have a high polar group to non polar group ratio), or have high Hydrogen bonding capability
What characterizes Acids?
- -They have more than 10-7M of [H+]
- -They have a pH below 7
- -They donate Protons (they are positively charged)
What characterizes Bases?
- -They have less than 10-7M of [H+]
- -They have a pH above 7
- -They accept Protons (they are negatively charged, proton defficient)
What is a Buffer?
- -a solution that resists ph change with the addition of
- acid or base.
- -Buffers arise from weak acids and bases
- -required to maintain physiological pH in cells and tissues
What are the two negatively charged ions in biomolecules?
Nitrogen and oxygen
How many Hydrogen ions are at the neutral pH?
A difference of one pH is a difference of how many [H+]?
10 times the [H+]
How do strong acids/bases and weak acids/bases dissociate differently in water?
- strong acids/bases dissociate completely
- weak acids/bases do not dissociate completely and the extent of dissociation can be quantified with
What is pKa?
- -the pH that the acid can donate a proton, the lower the pKa the stronger the acid
What is Ka?
- Ka is the equilibrium constant
How do weak acids Dissociate in water?
- [HA] weak acid
- [A-] conjugate base
what is the size of a buffering region?
When does pH=pKa?
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