MCB 2000 Final Exam Questions with
Guaranteed Pass Solutions 2025-2026
Updated.
Where does electron transport and oxidative phosphorylation occur in the mitochondria? -
Answer inner mitochondrial membrane
What are the complexes if the ETC? - Answer Complex I - NADH-Q oxidoreductase
Complex II - Succinate-Q reductase
Complex III - Q-cytochrome c oxidoreductase
Complex IV - Cytochrome c oxidase
What are the important redox centers and their roles? - Answer - FMN (similar to FAD,
Flavoproteins) - 2-electron acceptor but only pass one electron at a time
- Cytochromes/Heme (b, c, c1a and a3) - one electron transfers
- Fe-S proteins - one electron transfers
- Protein-bound copper - one electron transfer
Characteristics of Coenzyme Q - Answer -Mobile electron carrier, isoprenoid hydrophobic tail
- quinone function group; undergoes oxidation-reduction, produces one electron at a time
Characteristics of cytochrome c - Answer -small protein on outer side of inner membrane
-carries electron to complex IV
Importance of reduction potential of carriers in determining flow - Answer the reduction
potentials farther down stream are more likely to accept electrons, successive transfers are
exergonic
Standard free energy change of carriers - Answer related to the change in reduction
potential
deltaG' = -nF deltaE'0
, How do cells defend against ROS? - Answer Enzymatic mechanisms - Superoxide dismutase,
Catalase, GSH peroxidase paired with GSH reductase
Non-enzymatic mechanisms - Vitamin E ( lipid soluble, protects against lipid peroxides), Vitamin
C (water soluble, important for regeneratin reduced form of Vitamin E
What is the Chemiosmotic hypothesis and why is it important? - Answer Peter Mitchell's
hypothesis - generation of electrochemical gradient due to differences in proton concentration
and charge differences across inner mitochondrial membrane that drives ATP synthesis
How does ATP synthase function? - Answer Proton diffusion through the pore drives it by
entering half channel from cytoplasm, causing COO protonation, c ring rotates and proton exits
into matrix, COO is restored
Has three different conformations
- L - ADP and P bind to loose conformation
- T - converts ADP and P to ATP, ATP bound tightly
- O - open form binds or releases
How does ADP regulate oxidative phosphorylation? - Answer ADP concentration controls
rate at which O2 is consumed, electrons do not flow unless ATP needs to be
synthesized/consumed. ATP synthesis is dependent on its rate of utilization
What is the coupling between ATP synthase and electron transport? - Answer ATP generation
is critically dependent of electron flow and Electron flow only occurs when ATP can be
synthesized
What is the implications of ATP synthase and electron transport coupling? - Answer
[ATP]/[ADP] ratio plays role in regulating the activity of the ETC and ADP regulates the rate of
oxidative phosphorylation since other molecules are rarely rate-limiting
What is the significance of respiratory control? - Answer - Rapid consumtion of ATP for
cellular work leads to decreased ATP and increased ADP. Oxid. Phos is favored
thermodynamically and kinetically
- As ATP accumulates in the cell, ADP is decreased and electron transport is slowed. Reduced
coenzymes increase and oxidized coenzymes decrease (no longer available as acceptors). This
leads to a throttling of respiratory metabolism.
- Net effect: coupling of oxid. phos. with cellular needs for ATP by ADP-mediated respiratory
control
Guaranteed Pass Solutions 2025-2026
Updated.
Where does electron transport and oxidative phosphorylation occur in the mitochondria? -
Answer inner mitochondrial membrane
What are the complexes if the ETC? - Answer Complex I - NADH-Q oxidoreductase
Complex II - Succinate-Q reductase
Complex III - Q-cytochrome c oxidoreductase
Complex IV - Cytochrome c oxidase
What are the important redox centers and their roles? - Answer - FMN (similar to FAD,
Flavoproteins) - 2-electron acceptor but only pass one electron at a time
- Cytochromes/Heme (b, c, c1a and a3) - one electron transfers
- Fe-S proteins - one electron transfers
- Protein-bound copper - one electron transfer
Characteristics of Coenzyme Q - Answer -Mobile electron carrier, isoprenoid hydrophobic tail
- quinone function group; undergoes oxidation-reduction, produces one electron at a time
Characteristics of cytochrome c - Answer -small protein on outer side of inner membrane
-carries electron to complex IV
Importance of reduction potential of carriers in determining flow - Answer the reduction
potentials farther down stream are more likely to accept electrons, successive transfers are
exergonic
Standard free energy change of carriers - Answer related to the change in reduction
potential
deltaG' = -nF deltaE'0
, How do cells defend against ROS? - Answer Enzymatic mechanisms - Superoxide dismutase,
Catalase, GSH peroxidase paired with GSH reductase
Non-enzymatic mechanisms - Vitamin E ( lipid soluble, protects against lipid peroxides), Vitamin
C (water soluble, important for regeneratin reduced form of Vitamin E
What is the Chemiosmotic hypothesis and why is it important? - Answer Peter Mitchell's
hypothesis - generation of electrochemical gradient due to differences in proton concentration
and charge differences across inner mitochondrial membrane that drives ATP synthesis
How does ATP synthase function? - Answer Proton diffusion through the pore drives it by
entering half channel from cytoplasm, causing COO protonation, c ring rotates and proton exits
into matrix, COO is restored
Has three different conformations
- L - ADP and P bind to loose conformation
- T - converts ADP and P to ATP, ATP bound tightly
- O - open form binds or releases
How does ADP regulate oxidative phosphorylation? - Answer ADP concentration controls
rate at which O2 is consumed, electrons do not flow unless ATP needs to be
synthesized/consumed. ATP synthesis is dependent on its rate of utilization
What is the coupling between ATP synthase and electron transport? - Answer ATP generation
is critically dependent of electron flow and Electron flow only occurs when ATP can be
synthesized
What is the implications of ATP synthase and electron transport coupling? - Answer
[ATP]/[ADP] ratio plays role in regulating the activity of the ETC and ADP regulates the rate of
oxidative phosphorylation since other molecules are rarely rate-limiting
What is the significance of respiratory control? - Answer - Rapid consumtion of ATP for
cellular work leads to decreased ATP and increased ADP. Oxid. Phos is favored
thermodynamically and kinetically
- As ATP accumulates in the cell, ADP is decreased and electron transport is slowed. Reduced
coenzymes increase and oxidized coenzymes decrease (no longer available as acceptors). This
leads to a throttling of respiratory metabolism.
- Net effect: coupling of oxid. phos. with cellular needs for ATP by ADP-mediated respiratory
control
