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Cell Biology Quiz#3: 20 points
Answer any FOUR of the following Five Questions:
1) What is the optimal yield when a single pyruvate undergoes complete oxidation in the mitochondria? 5 pts
Cytosolic Reactions:
GTP or ATP= 4ATP-2ATP = 2 ATP yield
NADH= 2
FADH2= 0
CO2= 0
Mitochondrial Reactions:
GTP or ATP= 1 = 1 GTP
NADH= (1 pyruvate dehydrogenase+ 3 TCA) X 3ATP/NADH = 12 ATP
FADH2= 1 FADH2 X 2ATP/FADH2 = 2ATP
CO2= (1 pyruvate dehydrogenase + 2 TCA) = 3 CO2
Total ATP Produced following electron transport by all of the above mitochondrial
reactions:___1+12+2=15ATP
2) Draw a diagram that shows with names or numbers the specific enzymes and pathways that feed electrons
from FADH2 into electron transport and chemiosmosis? About how many protons are required for each
ATP to be synthesized? Show the chemical reaction that represents the final destination for these electrons at
the end of the pathway? 5 pts
3) How many acetyl-CoA, NADH and FADH2 would be produced if a 18 carbon long fatty acid (stearic acid
underwent beta-oxidation and TCA? What is the total yield of ATP following electron transport and
chemiosomosis? 5 pts
Acetyl-CoA= Nine (18 carbon chain makes nine two carbon acetyl-CoA molecules)
NADH= 8 (B-oxidation)+ 27 (TCA) = 35 NADH
FADH2= 8 (B-oxidation) + 9 (TCA) = 17 FADH2
GTP= 9 TCA
CO2= 18 total TCA
Total ATP following chemiosmosis made possible by all of the above reactions:_____148_______
35 NADH X 3= 105 ATP 17 X 2 = 34 ATP
9 GTP9ATP Total=105 + 34 + 9 = 1 ATP
4) Compare and Contrast the Structure and Function of a mitochondria and a chloroplast with respect to
number of membranes, names of structures, directions of proton gradients, and the use of NAD/NADP (5
points).
Mitochondria and Chloroplast both contain DNA of prokaryotic origins, they both generate proton gradients and
they both use a ATP-synthase that is dependent on a proton gradient.
Mitochondria contain two phospholipid bilayers (outer is porous, inner is very selective, 4 PL monolayers). They
use energy from electron transport H+ out of matrix to the cristae, with oxygen as the final e- acceptor. The H+
leak back into the matrix through the ATP-synthase, such that the negative delta G is used to synthesize ATP
(ADP+PiATP).
In contrast, the chloroplast contains THREE PL bilayer (6 PL monolayers). The trick is that they use energy from
light to excite electrons (Photosystem II) to strip an electron from water to create O2. The energy in the electron is
used drive proton pumps that push H+ into the lumen of the thylakoid discs making them acidic on the inside. The
protons are allowed to leak back out of the thylakoid discs (run down their conc. Gradients) by passing through an
ATP-synthase (ADP+Pi ATP). The electrons are re-excited by light (Photosystem I) such that the final step is the
production of NADPH (not NADH).
5) Compare and Contrast the Light and Dark Reactions with regards to their reactants, products, and their
requirements for photons of light or ribulose-1,5-bisphosphate (5 points)
The light reactions require light to remove an electron from water to make oxygen in Photosystem II, then use the
energy to create a proton gradient that is used to generate ATP, then use additional light to re-excite the electron in
photosystem I and ultimately create NADPH. These reactions stop in the absence of light.
The Dark reactions use accumulated ATP and NADPH to fix three carbon dioxides to pre-existing three ribulose1,5-bisphosphate (3X5-carbons) and create six 3-phosphoglycerates (6X 3carbons=18 carbons). For every six 3PGs created by carbon fixation, one glyceraldehyde-3-phosphate (G-3-P) or dihydroxyacetone phosphate (DHP)
can be produced and removed from the system such that the original three ribulose-1,5-bisphosphates can be
regenerated. When G-3-P and DHP accumulate the delta G favors the synthesis of fructose-1,6-bisphosphate and
gluconeogenesis permits the fixed carbons to be convereted to glucose, starch or what ever the plant needs. The
key is that carbon fixation ONLY occurs if pre-existing ribulose-1,5-bisphosphate is ready to accept it.
Extra Credit) Consider TCA, name all the enzymes, and draw each structure for all products/reactants that
permit one pyruvate to become oxidized in TCA. (2 points)
TCA only occurs in the mitochondria-Glycolysis/gluconeogensis only occurs in the cytosol
Remember that the Delta G values for a set of half reactions are only additive if they occur in the same
intracellular compartment (no membranes in between), hence what happened in the cytosol for glycolysis and
additive delta G is not additive to what happened in the mitochondria.