Buffers, Peptides & enzyme kinetics

-log[H3O+]

ph formula

-logka

pka formula

weak acid

if ph<pka dominant is

weak acid = conjugate base

if ph = pka dominant

conjugate base

pH > pka dominant species is

Buffers

resist drastic changes in ph

HA + saltA- / B + saltHB-

two types of component of buffers

HA + H2O ←→ A- + H3O+; B + H2O ←→ BH+ + OH-

dissociation eqation f

H3O+ + A- → H2O + HA; H3O+ + HB- → H2O + B

Increasing H3O

OH- + HA → H2O + A-; OH- + BH → B + H2O

Increasing OH

pH = pka + log [A]/[HA]

general ph equation

C x V x f x MM

mass of solid reg

(C x V x f x MM) / p

vol of reagent

((CbufferVbuffer)/Stock)*f

volume of component stock solution

Peptides

polymers of amino acids, condensation reaction of amino acids resulting to the formation of a peptide bond

Peptides/Oligopeptides

continuous chains of a few amino acids usually not more than 50 residues

Polypeptides

amino acid chains less than 10000 Da MW

Proteins

large amino acids > 10000 Da

Restricts rotation around peptide bond, permits rotation around c-n and c-carbonyl angle, coplanar

consequences of peptide bone

deprotonated

if pka of ionizable group < pH

ionizable

if pka for ionizable groub > pH

basic/ acidic

All deprotobated amino acid and carbonyl groups in the peptide bonds are no longer ____ or _____

Insulin

hormone for glucose absorption

Oxytocin

love hormone, contraction of uterine

Vasopressin

nonpeptide, prevents urination

Aspartame

dipeptide aspartylphenylalanyl methyl ester as an artificial sweetener

Phenylketonuria

cannot metabolize phenylalanine due to low levels of phenylalanine hydroxylase pHe to tyr, mental nonon

Enzyme activity

rate/velocity of the enzyme-catalyzed reaction. Measured at the beginning, initial velocity Vo

(d[P])/t = -dS/t

Rate Vo

substrate concentration, temperature, pH, Presence of inhibitors

factors affecting enzyme activity

Substrate concentration

rate of an enzyme-catalyzed reaction increases with substrate concentration until Vmax is reached. It is reached when all enzymes are involved in the ES complex

Temperature

optimal _________ peak higher ke moves more and higher chances of collisions. Enzyme activity  decrease with increased ____ as it denatures enzymes

pH

requires ionized. Same trend as temperature

Vo

product v time, slope of the linear portion of the graph slope = this

Vmax

fastest rate by which the enzyme can catalyze the reaction. = 1/y-intrp

Michaelis constant, KM

substrate concentration that produces half maximal velocity. Smaller km means that small amount of substrate is needed to obtain complex. High affinity for the substrate. = 1/x-interp

Vo = (Vmax[S])/(Km + [S])

Michaelis-menten equation

1/Vo = 1/vmax + 1km/vmax[1/S]

lineweaver-burke equation

Reversible

type of enzyme inhibition where it can dissociatiate from an enzyme

Irreversible

type of enzyme inhibition that covalently binds to the enzyme to make it retard.

Competitive inhibition

takes the space of the active site which prevents the substrate from binding to the enzyme. 

Vmax stays the same, Km increases

Vmax and Km in terms of competitive enzyme

non-competitive inhibition

does not bind to the active site

km is unchanged, vmax decreases

vmax and km in terms of non-competitive