Water and Molecular Interactions Flashcards
Organisms are ___-___% water
70/90
Water is held together by ____ bonds
Hydrogen
____ biomolecules are highly soluble in water
Polar
Why do polar molecules dissolve better in water than non polar?
Nonpolar biomolecules interfere with the water-water interactions, they decrease the entropy
What are some characteristics of water? Why?
- Relatively high melting, boiling, and vapour point
- High surface tension
Caused by attractions between individual water molecules
In water molecules the hydrogen have partial ____ charges and the oxygen has a partial _____ charge
Positive/negative
Why do water molecules have high attraction to each other?
Their partial positive and negative charges attract between molecules
When water is heated, bonds break and reform _____. Cohesion is ______.
Rapidly/high
Why doe side have a high melting point?
Water molecules are held in place by a crystalline structure
What is ΔH?
Enthalpy change
What is ΔG?
Change in free energy
What is Δs?
Change in entropy
Melting and evaporation occur ______ at room temperature, why?
spontaneously, tendency to bond is outweighed by the push to randomness
During melting or evaporation ______ increases
Entropy
H bonds for between _____ and _______, this excludes bonds formed between ______ and _______, which are weakly polar
hydrogen/electronegative atoms/hydrogen/carbon
What other types of solutes does water readily dissolve (aside from polar solutes)? How?
- Charged solutes, done by stabilizing the ions which weakens the electrostatic interactions between them which limits their tendency to bond
- compounds with functional groups, done by replacing the solute-solute H bonds
H bonds are strongest in a ______ line
Straight
What are amphipathic biomolecules? Include examples
Molecules that are stabilized by their hydrophobic effect, they are important structural determinants, they have both hydrophobic and hydrophilic parts
-ex. proteins, pigments, some vitamins, sterols, membrane proteins
Van der Waals interactions happens when two _____ molecule are brought close to each other, their _____ _____ influence each other, creating random ______ generation in both atoms which makes weak ______.
uncharged/electron clouds/dipole/attractions
Each atom has a distinct Van der Waals _____
radius
_______ and _______ bonds depend on solvent _____ an H ______
ionic/H/polarity/alignment
Solutes can alter _____ _____ of solvents because they change the _____ of the solvent. These include ____ ____, ______ ______, ______ ______, _____ _____, and _____ _____.
Physical properties/concentration/melting point/boiling point/freezing point/osmotic pressure/vapour point
In a hypertonic solution, water _____ the cell because solute concentration in the cell __ solute concentration outside the cell.
This causes animals cells to _____ and plant cells to _____.
leaves/<
shrivel/shrivel
In hypotonic solution, water ____ the cell because solute concentration inside __ solute concentration outside.
This causes animal cells to ____ and plant cells to become ______ which is ____.
enters/>
lyse/turgid/ideal
In isotonic solutions, water _____ and ____ the cell at an ____ rate, solute concentration outside cell __ solute concentration inside cell.
This causes animal cells to be ____ and plant cells to be _____.
enters/exits/=
normal/flaccid
Water ionizes to ___ and ___, this is described by the ___ constant. Pure water is ____ ionized.
H+/OH-/slightly
Weak ____ that dissolve in water contribute ___, called ____. Weak ____ consume ___, called ____.
acids/H+/ionizing/bases/H+/protonating
Water ionization is _____.
reversible
pH: total ___ ______ from all sources in a solution
H+ concentration
Even though H2OH+ +OH- is commonly shown as the equation for water ionization, ____ does not naturally exist in H2O and form ____ immediately instead
H+/H3O+ (hydronium ions)
How can ionization be measured?
Electrical conductivity
What is the equilibrium constant?
Keq: the position of equilibrium for every equation
Keq=[product of products Keq]/[product of reactants Keq]
Ions ____ ____ in their individual directions based on _____, since ___ is especially fast is explains why acid/base reactions are so fast
proton hop/charge/H+
Ionic product of water (Kw) = ?
Kw = Keq[H2O] = [H+][OH-] = 110^-14 M^2
pH = ?
pH = -log[H+] pH = 14-pOH
pOH = ?
pOH = -log[OH-] pOH = 14-pH
Strong acids and bases ionize ____.
Completely
Acids are proton ____ and bases are protons _____.
Donors/acceptors
Conjugate acid-base pairs:
Acids that pair with a base to donate and accept electrons, these are reversible reactions
The tendency of an acid to lose a proton and form its conjugate base is defined by:
Keq = [H+][A-]/[HA] = Ka
Ka represents …
the acid dissociation constant
pKa = ?
pKa = -log[Ka] (analogous to pH)
How can pKa for weak acids be found on a titration curve?
It is equal to the pH value then the reaction is at 50% OH- added, the point where concentration of proton donor = proton acceptor
What is the buffering region? Where can it be found on a titration curve?
It is the region where the amount of base added makes very little difference to the pH, usually surrounding the pKa point on a titration curve in the area that is mostly horizontal
Titration ends when pH=__ and all protons are _____
7/converted
