Functional Groups and Water/H-bonding

What is an acid?

• electron acceptors

• proton donors

What is a base?

• electron donor

• proton acceptor

pka of sulfonic acid

1

pka of carboxylic acid

5

pka of phenol

10

pka of aliphatic amine (technically its CA)

10

pka of aromatic amine (technically its CA)

5

What does the Henderson-Hasselbach equation measure?

the relationship between pH and pKa
- pH = variable depending on environment
- pKa = constant value

pH of mouth, stomach, intestine, and blood?

mouth = 6
stomach = 1-3
small intestine = 6-8 blood = 7.4 (7.35-7.45)

Hepatic Portal System

blood flow between liver an GI tract

Rule of 9s

difference of pH and pka = # of 9s for ionized/unionized ratio
- if difference = 0 = 50:50
- difference = 1 = 90:10
- difference = 99:1
etc

Dipole

partial positive and partial negative charges (weak charges)

partial charges and full charges favor …..

water solubility

polar substances (do/do not) dissolve in water
nonpolar substances (do/do not) dissolve in water

• polar = do

• nonpolar = do not

solvation shell

shell of H₂O surrounding charged atom
-maximizes solute-solvent H-bonding
- if hydrogen bonding is not possible —> water squeezes substances (ex. oil) out

What is the Henderson-Hasselbach Equation?

pH = pKa + log₁₀[unprotonated/Protonated] ?

is phenol acidic or basic?

acidic
-OH = ability to donate an H+

is an aliphatic amine acidic or basic?

basic

what is a hydrogen bond?

electrostatic attraction between the oxygen atom of one water molecule and the hydrogen of another

hydrogen bonding is relatively (weak/strong)

weak

Hydrogen Bonds Account for the ….

Relatively High Melting Point of Water

Hydrogen acceptor and Hydrogen donator

acceptor = electronegative atom
ex. C=O, N, O, C=O,

donor = hydrogen atom covalently bonded to another electronegative atom
ex. O-H , N-H

amphipathic

has regions that are polar/charged and regions that are nonpolar
- ex. AA

are straight or bent hydrogen bonds stronger?

straight

hydrophilic definition

compounds that dissolve easily in H2O
- generally charged or polar compounds hy

hydrophobic definition

nonpolar molecules such as lipids and waxes

Which gases are nonpolar?

CO2, O2, N2

which amino acids are not soluble in aqueous solutions?

• hydrophobic + nonpolar amino acids (carbon chains w/ no dipoles)

  • 7 aliphatic AA

    • GAVLIP (M)

      • GLY/G, ALA/A, VAL/V, LEU/L, ILE/I, PRO/P, MET/M

  • 3 aromatic

    • PTT

      • PHE/F, TYR/Y, TRP/W

Which amino acids are capable of H-bonding?

• neutral (uncharged) polar amino acids (can perform dipole-dipole interactions)

  • amides

    • GLN/Q, ASN/N

  • sulfonic

    • CYS/C

  • Alcoholic

    • SER/S

    • THR/T

which amino acids are soluble in aqueous solutions?

• polar AA

  • neutral

    • STAGC (Serine, Threonine, Asparagine, Glutamine Cysteine)

  • charged

    • positive

      • HAL (Histidine, Arginine, Lysine)

    • negative

      • ED (Glutamate/Glutamic acid, Aspartate/Aspartic acid)

hydrophobic effect

• nonpolar regions cluster together

  • polar regions arrange to maximize interactions w/ each other + solvent

Hydrogen bonds are between _______

• neutral, polar groups

• peptide bonds
  

Where is H-bonding found in protein structures?

• secondary structures

  • alpha helix (n + (n+4) )

  • beta sheets (n + (n+3) )

ionic interactions

attraction + repulsion
- bonds in peptides (primary structure, ionized COO- & NH3+)

Van der Waals interaction / London Dispersion forces

• distance-dependent weak attractions + repulsions between transient dipoles

  • any 2 atoms in close proximity

Hydrogen bonds are covalent/noncovalent

noncovalent