3 Flashcards
(23 cards)
ph formula
-log[H]
why is pH important for biochemical molecules
functional groups can also act as weak acids or bases, losing and accepting H+ at different pH. this affects noncovalent interactions
Ka formula
[H+][A-]/[HA]
strong acid Kas and pKas are…
Kas are high and pKas are low
pKa measures
strength of acid
what happens if pH is above the pKa
will be deprotonated. if lower, protonated
handerson hasselbach equation
pH = pKa + log [A-]/[HA]
how do buffers work
by neutralizing small additions/loss of H+
at what range are buffers most effective
+/- one pH unit around pKa
physiological pH
7.4
stomach pH
1.5-3.5
do all cells die in acidic or alkaline environments
no
how to select a buffer
choose one with pKa closest to the pH you need at a given temperature, make sure it is chemically stable and will not produce molecules that affect experiment, check cost and avaliability
zwitterion
neurtral molecule with separate positive and negatively charged functional groups
which amino acids are not zwitterions at physiological pH
d, e, r, k
how many functional groups on histidine can be deprotonated and protonated
3 functional groups
isoelectric point
pH when the charge is 0
how to find the pKa based off of titration curve
find the pH in the middle of the flat buffer region
what does it mean when pKa = pH
there are the same number of the two species on either side of the arrow
what do the steep increase parts of titration curves mean
pure compound
how to find pI based off of titration curve
average 2 pKa values around the neutral molecule
main buffering species in blood, how does it buffer
bicarbonate (HCO3-), excess H+ creates H2CO3, which breaks down to form H2O and CO2 (exhaled). it can also become CO3(2-), a weak acid
bohr effect
pH can affect oxygen carrying ability of hemoglobin, because at low pH, there is an extra proton that changes structure and releases O2.
