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 acid pKa = 3.5 (strong acid!) Carbonic anhydrase Zn-dependent, rate = 10 6 /s pH drops helps O 2 release

often in cat. center, good H+ acceptor disulfide bonds pigments, thyroid hormones

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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,

Example: The antibiotic Deoxycyclin is a noncompetitive inhibitor of collagenase and is used to treat peridontal disease Unproductive reaction = at same amount of substrate, you dramatically lower Vmax, binds enzyme in absence and presence of substrate

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

Catalytic triad: Asp positions His, His extracts hydrogen from Ser, Ser attacks carboxyl-terminal side of Trp, Tyr, Phe or Met (large hydrophobic residues) Chymotrypsin has highly reactive Ser residue

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

Increasing potential to accept electrons Complex I II III IV ubiquinone

outside inside

You make 30 ATPs/1glucose

Acyl carrier protein

Diabetic ketosis in the absence of insulin