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What are waters active roles in biological systems?
Water is a participant in many biochemical reactions
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What are waters passive roles in biological systems?
The structures of biomolecules (proteins, membranes, nucleic acids) are in response to their interaction with water
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Why is water a dipole?
- O has partial (–) charge
- H has partial (+) charge
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Hydrogen Bonds
- -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
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How many Hydrogen Bonds can a water molecule make?
- -4
- -Water can donate two hydrogen bonds and accept two hydrogen bonds.
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What contributes to waters high heat of vaporization and high specific heat capacity?
The large number of hydrogen bonds
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What are Amphipathic molecules?
- molecules that have hydrophobic chains and ionic or polar
- ends.(lipids)
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What is the Hydrophobic effect
the exclusion of nonpolar substances by water (critical for protein folding and membrane formation)
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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
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What characterizes Acids?
- -They have more than 10-7M of [H+]
- -They have a pH below 7
- -They donate Protons (they are positively charged)
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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)
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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
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What are the two negatively charged ions in biomolecules?
Nitrogen and oxygen
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How many Hydrogen ions are at the neutral pH?
10-7M
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A difference of one pH is a difference of how many [H+]?
10 times the [H+]
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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
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What is pKa?
- -the pH that the acid can donate a proton, the lower the pKa the stronger the acid
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What is Ka?
- Ka is the equilibrium constant
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How do weak acids Dissociate in water?
- [HA] weak acid
- [A-] conjugate base
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what is the size of a buffering region?
- 2pH
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When does pH=pKa?
when [A-]=[HA]
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