Practice Quiz and homework
Answers!!
Case study answers
• 1. retenone killed the girl (fleacide)
• 2. girl must have had unusual exposure or high
dose... Ingestion or aspirated. Lungs are highly
vascularized causing rapid dispersal of poison.
• 3. Autopsy showed cell death in specific
tissues suggesting that damage was at the
cellular level.
• Damage to mitochondria specifically = aerobic
respiration disrupted
Case study answers cont.
Part 3
• Normal levels of acetyl coenzyme A indicate
that glycolysis is functioning normally.
• No ATP from mitochondria = either Krebs or
electron transp were impaired.
• Low levels of NAD+ and high NADH = first step
is affected. –NADH dehydrogenase must be
blocked.
Part 4 #2, 3
• Inada (NAD) drug would likely ...
• Not help since the real problem is that
retenone prevents the transfer of electrons
from NADH to the e- transp. Chain by
inactivating NADH dehydrogenase.
• NAD would help make more NADH, but chain
would still be inoperable.
• AR would not help.
Quiz Answers
1. A
2. C
3. D
4. C
5. E
6. B
7. B
8. A
9. E
10.a
11.c
12. c
13.e
14. C
15. D
16. B
17. D
18. E
19. A
Homework answers
#7. Compare substrate-level phosphorylation and
oxidative phosphorylation.
• S.L.P. generates ATP directly from an enzyme
catalyzed reaction, whereas O.P. generates ATP
indirectly by the chemiosmotic potential created
• The process is oxidative because, it involves several
sequential redox reactions, with oxygen being the
final electron acceptor.
• It is more complex than S.L.P., and it produces more
ATP.
#8. Why is aerobic respiration a more efficient energyextracting process than glycolysis alone?
• Glycolysis only transfers about 2.1% of the free
energy available in 1 mol of glucose into ATP. Most
of the energy is trapped in 2 pyruvate and 2 NADH.
• Aerobic respiration further processes the pyruvate
and NADH during pyruvate oxidation, the Krebs
cycle, chemiosmosis, and ETC. By the end of aerobic
respiration, all the energy available in glucose has
been harnessed.
#9 a) What part of a glucose molecule
provides electrons in cellular respiration?
Hydrogen atoms
B) Describe how E.T.C. set up a proton gradient in
response to electron flow.
•
•
•
•
•
The ETC passes protons from the mitochondrial matrix to
the intermediate space.
NADH gives up the two electrons it carries to NADH
hydrogenase.
Electron carriers, ubiquinone and cytochrome c, shuttle
electrons from NADH hydrogenase to cytochrone b-c1
complex to cytochrome oxidase complex.
Free energy is lost from the electrons during each step in
this process, and this energy is used to pump H+ from the
matrix into the intermembrane space.
The final step in the electron transport chain sees oxygen
accept 2 electrons from cytochrome oxidase complex, and
it consumes protons to form water.
Many are confused how sometimes 36 ATP are
produced and sometimes 38 ATP are produced.
• REMEDIATION: Two different types of shuttle exist:
– Since the inner mitochondrial membrane is impermeable to NADH
(from glycolysis), it has two shuttle systems that pass electrons
from cytosolic NADH in the intermembrane space to the matrix
– The first and most common shuttle, called the glycerol-phosphate
shuttle, transfers the electrons from cystolic NADH to FAD to
produce FADH2 (resulting in the synthesis of 2 ATP molecules).
– The second shuttle, called the aspartate shuttle, transfers
electrons to NAD+ instead of FAD, forming NADH (resulting in the
synthesis of 3 ATP molecules).
c) How is the energy used to drive the synthesis of ATP?
• The protons that accumulate in the intermembrane space
create an electrochemical gradient.
• The gradient has 2 components: electrical caused by a
higher positive charge in the intermembrane space than in
the matrix, and a chemical gradient created by a higher
concentration of protons in the intermembrane space.
• The electrochemical gradient stores free energy; the
proton-motive force (PMF).
• The mitochondrial membrane is almost impermeable to
protons, so the protons are forced to pass through ATP
synthase, reducing the energy of the gradient.
• The energy is used by the enzyme ATP synthase to create
the 3rd phosphate-ester bond forming ATP.
d) What is the name of this process?
• Chemiosmosis (oxidative phosphorylation)
#10. A) Distinguish between an electron carrier and a terminal
electron acceptor.
10. b) What is the final electron acceptor in aerobic respiration?
a) An electron carrier is first oxidized and then
reduced by a more electronegative molecule.
A terminal electron acceptor is only reduced
(it is at the end of the ETC)
b) oxygen
11. Explain how the overall equation for cellular
respiration is misleading.
• It does not include the numerous enzymes,
coenzymes, and intermediate chemicals involved in
the process.
• It also shows the conversion of glucose and oxygen
to carbon dioxide and water as a simple, one-step
process, where it is actually much more involved
than that.