Transcript Document

Concepts in biochemistry
Review session Nov. 26, 2007
pH = -log [H+] concentration of hydrogen ions
pKa = -log Ka susceptibility for hydrogen removal
Ka is proton dissociation constant Ka = [H+] [A-]/ [HA]
pH = pKa when acid HA is HALF neutralized and you have
as much acid as ions
Carbonic anhydrase
Zn-dependent, rate = 106/s
Carbonic acid
pKa = 3.5
(strong acid!)
pH drops
helps O2
release
often in cat. center,
good H+ acceptor
disulfide bonds
pigments, thyroid
hormones
?
?
chemically what kind of bond?
Interactions between side chains shape tertiary structure of proteins
Interactions between individual polypeptides shape quarternary structure
Collagen
Enzymes don’t change the equilibrium only the RATE of an reaction
Catalysis
Substrate concentration at Vmax/2
Km=dissociation/association
Lineweaver-Burk 1/Vo=Km/Vmax x 1/s + 1/Vmax
High substrate concentrations
can outcompete the inhibitor
Unproductive reaction =
at same amount of substrate,
you lower Vmax,
binds enzyme in absence
and presence of substrate
Unproductive reaction =
at same amount of substrate,
you dramatically lower Vmax,
Example: The antibiotic Deoxycyclin is a noncompetitive inhibitor
of collagenase and is used to treat peridontal disease
IMPORTANT:
Allosteric enzymes DO NOT obey MM kinetics, because they
contain multiple subunits that affect each other (e.g., hemoglobin)
Chymotrypsin: Ser part of catalytic triad
Chymotrypsin has highly reactive Ser residue
Catalytic triad: Asp positions His, His extracts
hydrogen from Ser, Ser attacks carboxyl-terminal
side of Trp, Tyr, Phe or Met (large hydrophobic residues)
Niacin = Vit B3
FMP
AMP
TPP = thiamine pyrophosphate
Production of pyruvate
Net gain in glycolysis:
2ATP
2 NADHs
Dead end
The Cori Cycle
stimulated by insulin
Sources for
glucose
production
underlined
nucleotide metabolism
(to make nucleotides, NOT
to gain energy)
Electron transport chain in the mitochondria
Complex
I
Increasing
potential
to accept
electrons
II
ubiquinone
III
IV
outside
inside
You make 30
ATPs/1glucose
Acyl carrier protein
Diabetic ketosis in the absence of insulin