Water Flashcards
Name the four macromolecules.
Protein, carbohydrate, lipid, nucleic acids
What is the monomer unit of protein?
Amino acids
What is the monomer unit of carbohydrate?
Glucose
What is the monomer unit of lipids?
Glycerol and fatty acids
What is the monomer unit of nucleic acids?
Nucleotide
Name an example of protein in animals.
Insulin in pancreas
Name an example of carbohydrate in animals.
Glycogen in liver
Name an example of lipid in animals.
Fat surrounding the kidneys
Name an example of nucleic acids in animals.
DNA in the cell nucleus
Why do plants use starches for energy? Compare the process with glycogen break down.
Since they do not require as much energy, breaking down starches is a slower process than glycogen
Which is easier to carry around: fat or sugar? Why?
Fat since it consumes less energy than glycogen
In the proton hopping reaction, where does the equilibrium lie?
On the H2O + H2O side
What is the proton hopping (or ionization of water) reaction?
H2O + H2O –> H3O+ + OH-
What are the benefits of the high heat of vaporization of water?
- Good temperature regulator
- Good evaporative (requires massive amount of energy –> you don’t lose too much)
What are the benefits of the high specific heat capacity of water?
- Prevents dramatic temperature changes
- Good heat buffer
Name three physiochemical properties of the water molecule.
1) High heat of vaporization (2,260J/g)
2) High specific heat capacity (4.2 J/goC)
3) Boiling point is 100oC
Define electronegativity.
Electronegativity is the ability of an atom to attract electrons to itself.
What creates a dipole moment?
A difference in electronegativity between two atoms/molecules.
What are the consequences of a dipole moment?
- Partial negative charge on the more electronegative atom/molecule
- Partial positive charge on the least negative atom/molecule
What accounts for all the characteristics of water?
Hydrogen bonding
Define hydrogen bonding.
A hydrogen bond is a type of interaction between an electronegative atom and a hydrogen atom bonded to another electronegative atom.
Without hydrogen bonding, what would happen to water at room temperature?
Water would be gas at room temperature
Are hydrogen bonds static? What do they depend on?
No, the number of bonds change through time and depend on the temperature.
What happens when you freeze cells? What would happen to its organelles?
The cell would burst.
Lattices would form and puncture/damage the cells organelles.
How would you freeze cells without destroying them?
Cryopreservatives
Cover the material with cryoprotectant coating
Are hydrogen bonds stronger or weaker than covalent bonds?
Covalent > Hydrogen
What makes ice float on liquid water?
The crystal lattice structure makes ice less dense than liquid water
Describe Gibbs Free Energy Equation
Free Energy Change = Enthalpy Change - T(Entropy/Randomness)
Is a positive or negative enthalpy favorable? Why?
Negative, since it means that it does not require energy and thus can occur spontaneously
Why does ice turn to water and water turn to gas spontaneously if their enthalpy is positive?
Because the entropy (randomness) is superior to the enthalpy
Why does boiling water at 100oC stay at 100oC?
Because all the energy will go into breaking hydrogen bonds to transform H2O (liquid) into H2O (gas).
How will the boiling point of water change if the altitude increases? Why?
If the altitude increases, pressure decreases, less energy to bring water to bp, so bp decreases
How will the boiling point of water change if the altitude decreases? Why?
If the altitude decreases, pressure increases, more energy to bring water to bp, so bp increases
Why do we want relatively weak bonds for biological molecules?
Since they are reversible, they act like velcro
What does the expression “strength in numbers” mean in biochemistry?
Multiple weak bonds are very successful for biological molecules
Place the bond types in order of most energy, to least energy.
1) Covalent
2) Ionic
3) Hydrogen
4) Hydrophobic
5) Van der Waals
What is water a good solvent for? Why?
- Charged and polar (hydrophilic) substances
- Since it has a dipole moment
How will water act around polar substances?
It will reorient itself and form a non-permanent sphere of hydration
Name some examples of substances that water is a good solvent for.
- Amino acids and proteins
- Small Alcohols
- Carbohydrates
- Salts
Why is water a good solvent for salts?
Because the dissolution of salts is energetically favorable due to the increase in entropy.
What is water a bad solvent for?
- Nonpolar (hydrophobic) substances
Name some examples of substances that water is a bad solvent for.
- Nonpolar gases
- Fatty acids
- Oils and waxes
- Hydrophobic amino acids
- Solvents such as benzene, octanol, hexane
How will water act around nonpolar substances?
It will form a cage around nonpolar compounds and DECREASE entropy (thermodynamically infavorable)
What does amphipathic mean?
Containing both polar and nonpolar domains
What is a micelle?
Aggregate of amphipathic molecules in water
Why do amphipathic molecules arrange themselves in micelles?
- Decreases surface area exposed to water
- Entropy is increased (thermodynamically favorable)
- Creates a sphere of hydration
What is the hydrophobic effect? Name one of its biological consequences.
- Non-polar molecules fold together to minimize contact with water
- Protein folding
If the partition coefficient indicates that there is a higher concentration in octanol than in water, is the substance polar or non-polar?
Non-polar
If the partition coefficient indicates that there is a higher concentration in water than in octanol, is the substance polar or non-polar?
Polar
When do hydrogen bonds occur?
When a hydrogen atom is sandwiched between two electron-attracting atoms (usually O or N)
When do ionic bonds occur?
When two formal charges interact with each other
When do hydrophobic bonds occur?
Two non-polar components form a bond to minimize interaction with water
When do Van der Waals Interactions occur?
When uncharged atoms are brought close together, the electron density creates a dipole
What is pH?
The measure of the number of protons in an aqueous solution.
pH = -log(H+)
What is a conjugate base?
When a weak acid becomes deprotonated (A-)
What is a conjugate acid?
A protonated weak acid (HA)
What is a buffer? Why is it useful biologically?
- Aqueous solution with a highly stable pH.
- Buffers regulate pH
In a titration, what happens when HA and A- are equivalent?
- pH = pKa
- Buffers are optimal
What is the optimal buffering capacity? What is the buffering region?
- When pH = pKa (when HA = A-)
- +/- 1pH unit around pKa
What is a monoprotic system?
- changes between HA and A- occur with the loss/gain of a single proton
- One pKa
What is a triprotic system? Give an example.
- Changes between HA and A- occur with the loss/gain of three protons
- ex: H3PO4
If you add a base to a buffer, how would the concentrations change?
HA - base = new concentration of HA
A- + base = new concentration of A-
If you add an acid to a buffer, how would the concentrations change?
HA + acid = new concentration of HA
A- - acid = new concentration of A-
How does pH influence the absorption of drugs?
Where it is absorbed/How.
Ex: stomach is acid, but absorption only occurs when drug is in its conjugate base form, so no absorption in stomach
What is osmosis?
The movement of water or salts through a semipermeable membrane to reach equilibrium.
What does hypertonic mean for a cell?
Greater concentration of solutes outside of the cell, water moves out of the cell, which SHRIVLES
What does hypotonic mean for a cell?
Lesser concentration of solutes outside of the cell, water moves into the cell, which BURSTS
Why don’t plant cells shrivel or burst?
They have a cell wall that helps them adapt to large changes in osmotic pressure
What is the pH of blood?
7.34-7.45
The buffering capacity of a solution can be overcome by what?
By the addition of excessive acid or base
