Water, weak interactions and buffers

Question 1

What is water in living organisms?

Answer 1

• The most abundant molecule
• has both passive and active roles in biochemistry

Question 2

Passive

Answer 2

• 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

Question 3

Active

Answer 3

• Water is a participant in many biochemical reactions
  Ex. Peptide bond formation releases a water molecule

Question 4

Catabolic

Answer 4

needs water

Question 5

Anabolic

Answer 5

releases water

Question 6

Water with electronegativity

Answer 6

• Oxygen and hydrogen differ in electronegativity (oxygen more electronegative)
• oxygen has partial negative and hydrogen has partial positive
• perfect hydrogen bonding molecule

Question 7

Electronegativity

Answer 7

ability to pull electrons towards them

Question 8

Electrostatic interactions

Answer 8

charge interactions

Question 9

What does the dipole of a water molecule influence in its abilities?

Answer 9

• form electrostatic interactions with charged molecules
• form hydrogen bonds (including other water molecules)

Question 10

Hydrogen bonds

Answer 10

• 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

Question 11

How long are hydrogen bonds compared to a covalent bond?

Answer 11

about double the length

Question 12

Hydrogen bond strength

Answer 12

• 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

Question 13

When are water molecules the happiest?

Answer 13

When it is hydrogen bonded to as many other water molecules as it can be (4)

Question 14

What does a large number of hydrogen bonds in water contribute to?

Answer 14

heat of vaporization and specific heat capacity of water

Question 15

Heat of vaporization

Answer 15

amount of heat required to vaporize a liquid to boiling point
- how much energy into a system to turn water to gas

Question 16

Specific heat capacity

Answer 16

amount of heat required to raise temperature of a substance one degree (can gain energy without temperature going up)

Question 17

Most living organisms are isothermic

Answer 17

need to regulate and maintain their temperatures

Question 18

Water as ice

Answer 18

• each water molecule is hydrogen bonded with 4 other water molecules
• lower density than liquid water, it floats
• takes up more space

Question 19

Polywater

Answer 19

• high boiling point, and higher viscosity than normal water
• concern that it was self-propagating and used as weapon
• reflected influence of impurities

Question 20

Water as a solvent

Answer 20

• 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)

Question 21

What can functional groups that form hydrogen bonds, bond to?

Answer 21

within the same molecule, other biomolecules, or with water
- have higher stability in water

Question 22

hydrophilic

Answer 22

water loving molecules are polar (charge and hydrogen bonding capabilities)

Question 23

hydrophobic

Answer 23

water fearing molecules are non-polar

Question 24

Amphipathic molecules

Answer 24

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

Question 25

hydrophobic interactions

Answer 25

forces that hold non-polar regions of the molecule together

Question 26

hydrophobic drive

Answer 26

primary driving force in formation and stabilization of biomolecular structures (polar heads in water, non-polar tails in the middles stuck together)

Question 27

Non-covalent interactions enable:

Answer 27

• transient, dynamic interactions
• flexibility of structure and function (greater range for interactions)