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What are waters passive and active roles in biological systems?

Passive- the structures of biomolecules are formed in response to reactions with water
Active- water is a participant in many biochemical reactions


How does water have a permanent dipole?
What functions does this give water?

The O has a partial negative charge (δ-) and the H has a partial positive charge (δ+)

Because of the dipole water can form electrostatic interactions with charged molecules and can form hydrogen bonds

Water can flip to present either positive or negative end to a bi ding molecule


What are hydrogen bonds?

Electrostatic interactions between an electronegative atom with a hydrogen linked (donor) to another electronegative atom with a free electron pair (acceptor)

Noncovalent and relatively weak (5% strength of a covalent bond)


How do you find which element is the donor and acceptor in hydrogen bonds?

The donor will have a direct bond to a hydrogen (———) while the acceptor will have the hydrogen attach to its free electrons (- - - -)


Can water serve as an acceptor and a donor in hydrogen bonds?

Yes since it has two hydrogen’s bonds directly and two free electron pairs attached to the oxygen

It donates and accepts two hydrogen bonds


What determines if a hydrogen bond is strong or weak?

If the donor and acceptor line up straight, they are stronger
R—-O——H- - - -O (strong)

O (Weaker)


What is the heat of vaporization and specific heat capacity?

Heat of vaporization- the amount of heat required to vaporize a liquid at its boiling temp

Specific heat capacity- the amount of heat required to raise the temp of a substance one degree

The large number of hydrogen bonds in water contributes to making these high


What does isothermic mean?

Means to stay at constant temperature, most living organism need to regulate and maintain their temperatures

The high composition of water and high specific heat capacity helps us stay cool


What are the two reasons water is an extremely effective hydrogen bonder?

1. Water can both accept and donate hydrogen bonds
2. Waters small size allows it to adopt optimal positioning for geometry of hydrogen bonding


Which type of molecules have the greatest solubility in water?

Molecules that carry charge (- or +) and/or participate in hydrogen bonds (donors or acceptors)


What are amphipathic molecules?

Molecules that contain both hydrophobic and hydrophilic portions

Ex: fatty acids


What are the polarities of hydrophilic and hydrophobic

Hydrophilic- polar
Hydrophobic- non polar


What happens when an amphipathic molecule is mixed with water?

The polar hydrophilic region interacts favourably with water but the non-polar regions cluster together to present the smallest hydrophobic surface to water


What do non covalent forces influence?

- formation and stabilization of structures of bio molecules
- recognition/interactions of one biomolecule with another
- binding of reactants to enzymes


What’s the difference between hydrogen bonds and ionic (electrostatic) interactions?

Hydrogen bonds are electrostatic interactions but since there are so many hydrogen bonds they have their own class


What are the overall structures of molecules determined by?

By much weaker, non covalent interactions

These interactions enable dynamic interactions and flexibility or structure and function


What are Van Der Waals forces?

When two uncharged atoms are brought very close together their surrounding electron clouds influence each other


What is the hydrophobic effect?

It is the association of a relatively non polar molecule or group with other non polar molecules
The observed tendency of non polar substances to aggregate in aqueous solution and exclude water


What is the second law of thermodynamics?

The total entropy (disorder) of a system and its surroundings always increases in a spontaneous process


What happens with water molecules around hydrophobic molecules?

The water molecules are ordered more so the introduction of non polar molecules decreases the entropy of water then the association of non polar molecules with each other releases some ordered water molecules which increases the entropy and the non polar molecules are driven together


What does H2O form when dissociated?

H2O -> H3O+ + OH-


What is the equation for pH?

pH= -log (H+) = log 1/H+


How does a difference in pH relate to a difference in H+?

A difference of 1 pH equals a 10 fold difference in (H+)


If H+ = 10^-7, what does pH equal and is it neutral acidic or basic?

pH= 7 and it’s neutral


If H+ > 10^-7, what is pH and is it neutral acidic or basic?

pH < 7


If H+ < 10^-7, what is pH and is it neutral acidic or basic?

pH > 7


What is the difference between strong acids and bases and weak acids and bases?

Strong- dissociate completely in water
Weak- do not dissociate completely in water


What is the equation for pKa?
How does this affect the strength

pKa= -logKa

The lower the pKa, the stronger the acid


What is the buffering region?

A region on a titration curve chart that extends one pH unit on either side of the pKa point

The higher the buffering region, the weaker the acid


What is a monoprotic acid compared to a diprotic acid?

Mono- one buffering region
Di- two buffering regions