The pyruvate dehydrogenase complex catalyzes the following reaction:

pyruvate + coa + nad+ → acetyl-coa + co2 + nadh

we will discuss this enzyme in detail on class, but for now all you need to know is the overall reaction that it catalyzes.

in a spectrophotometer, nadh absorbs light at 340 nm, nad+ does not.

the beer-lambert law relates the absorbance of a solution to its concentration, and states that:

a = ε.c. l

where a is absorbance, ε is the molar extinction coefficient, c is concentration, and l is the path length of the solution in the spectrophotometer. in all the calculations that follow assume l = 1 (ie all measurements were made in a cuvette with a 1 cm path length), so l can effectively be disregarded (although not its unit).

the molar extinction coefficient for nadh is 6,300 litres/mol cm-1 [or (mol/litre)-1 cm-1 or m-1 cm-1]. the molar extinction coefficient is the absorbance of a 1 molar solution in a 1 cm path length cuvette.