Water, weak interactions and buffers Flashcards
What is water in living organisms?
- The most abundant molecule
- has both passive and active roles in biochemistry
Passive
- The structure of biomolecules form in response to interaction with water
- context in which biochemistry is going to act in the role of water
Ex. Protein folding is driven to bury hydrophobic residues
Active
- Water is a participant in many biochemical reactions
Ex. Peptide bond formation releases a water molecule
Catabolic
needs water
Anabolic
releases water
Water with electronegativity
- Oxygen and hydrogen differ in electronegativity (oxygen more electronegative)
- oxygen has partial negative and hydrogen has partial positive
- perfect hydrogen bonding molecule
Electronegativity
ability to pull electrons towards them
Electrostatic interactions
charge interactions
What does the dipole of a water molecule influence in its abilities?
- form electrostatic interactions with charged molecules
- form hydrogen bonds (including other water molecules)
Hydrogen bonds
- electrostatic interactions between an electronegative atom with a hydrogen covalently linked (donor) to another electronegative atom with a free electron pair (acceptor)
- oxygen and nitrogen are common (acceptors and donors)
Ex. N-H—-N
How long are hydrogen bonds compared to a covalent bond?
about double the length
Hydrogen bond strength
- hydrogen bonds are relatively weak but when there’s a lot is has a possibility of becoming extremely strong
- depends on its geometry
- anti-parallel sheets are more stable than parallel because there is better geometry
When are water molecules the happiest?
When it is hydrogen bonded to as many other water molecules as it can be (4)
What does a large number of hydrogen bonds in water contribute to?
heat of vaporization and specific heat capacity of water
Heat of vaporization
amount of heat required to vaporize a liquid to boiling point
- how much energy into a system to turn water to gas
Specific heat capacity
amount of heat required to raise temperature of a substance one degree (can gain energy without temperature going up)
Most living organisms are isothermic
need to regulate and maintain their temperatures
Water as ice
- each water molecule is hydrogen bonded with 4 other water molecules
- lower density than liquid water, it floats
- takes up more space
Polywater
- high boiling point, and higher viscosity than normal water
- concern that it was self-propagating and used as weapon
- reflected influence of impurities
Water as a solvent
- can interact and dissolve charged solutions through formation of layers
- small size and permanent dipole makes them versatile
- likes interacting with molecules similar to it (anything that carries a charge)
What can functional groups that form hydrogen bonds, bond to?
within the same molecule, other biomolecules, or with water
- have higher stability in water
hydrophilic
water loving molecules are polar (charge and hydrogen bonding capabilities)
hydrophobic
water fearing molecules are non-polar
Amphipathic molecules
contains both hydrophobic and hydrophilic portions (fatty acids)
- most biomolecules
- all are going to amphipathic and it’s whether it is more or less polar
hydrophobic interactions
forces that hold non-polar regions of the molecule together
hydrophobic drive
primary driving force in formation and stabilization of biomolecular structures (polar heads in water, non-polar tails in the middles stuck together)
Non-covalent interactions enable:
- transient, dynamic interactions
- flexibility of structure and function (greater range for interactions)
