Biochemistry 440
Fall, 2008
Problem Set 9
1. Calculate the ∆E for the following reaction under cellular conditions.
pyruvate + NADH + H+ lactate + NAD+
The cellular concentrations are [NADH]: 50 µM, [NAD+]: 540 µM, [pyruvate]: 380 µM,
[lactate]: 3700 µM.
What is ∆G for this reaction?
(For help with this problem, see page 515 of your book.)
2. A cell is treated with an inhibitor that allows the conversion of glyceraldehyde 3-
phosphate to 1,3 bisphosphoglycerate to proceed but blocks the production of NADH at
this step. What would be the net yield of ATP by a cell treated with this inhibitor if it is
fed glucose under aerobic conditions? Express your answer in moles of ATP per mole of
glucose. Show your reasoning.
3. A cell is treated with an inhibitor that completely blocks synthesis of ATP by ATP
synthase but does not block the ability of the enzyme to allow protons to flow across the
inner mitochondrial membrane. What would be the net yield of ATP from the inhibited
cell if it were fed glucose? Express your answer in moles ATP per mole of glucose. Show
your reasoning.
4. What is the yield of ATP in a respiring mammalian cell fed glucose and treated with
rotenone. Assume an unlimited supply of NAD+ to keep glycolysis and the citric acid
cycle going.
5. This problem is a fun one. It will help you learn fatty acid catabolism for the final.
Enjoy!
Ruby-throated hummingbirds are members of the elite jet-set among birds who fly south
for the winter. They spend their summers in the Eastern United States and their winters in
Central America. In the early 1950's, controversy raged among ornithologists about their
migratory route. Did they take the overwater trip across the Gulf of Mexico to the
Yucatan Peninsula (a distance of 780 km if one takes off from New Orleans), or did they
merely hop along the Texas shore route, a distance of approximately 1950 km? (I don't
know why ornithologists failed to mention the less strenuous 2-staged journey from
Florida with a stopover in Cuba: Ruby-throated hummingbirds have been observed on the
Florida Gulf coast.) The shore route takes much longer but has unlimited food supplies
along the way. The transgulf route is faster, but for 780 km, there is no food. In
preparation for migration, the Ruby-throat lays down fat deposits by eating voraciously
for about 2 weeks before it migrates. This premigratory fat deposition is triggered by a
hormonal response to the shortening (Fall) or lengthening (Spring) of the daylight period,
which drastically increases their appetite. After these 2 weeks, a premigratory
hummingbird weighs 5 grams, 40% of which is fat. This fattening suggests that they
choose an overwater route. Analysis of the composition of these fat deposits (made on
migratory victims of head-on collisions with obstacles at airports during lousy weather
conditions) showed C14, C16 and C18 saturated fatty acids as well as C18 unsaturated
fatty acids. Some additional facts: hummingbirds have been clocked at 75 km/hr and their
metabolic rate at this speed, based on oxygen consumption data, has been calculated to be
4.00 kJ per hour of flight (for an averaged-sized bird). This energy expenditure is derived
entirely from ATP hydrolysis to ADP and Pi, and is the sole source of power for muscle
contraction. Using the data given above and the tables below, answer the following
