BIOCHEMISTRY ACS EXAM|VERIFIED QUESTIONS AND CORRECT DETAILED
ANSWERS|RATED AND GRADED A+ NEW UPDATE| 2026/2027
NADH - ANSWER✔ the reduced form of NAD+; an electron-carrying molecule that functions in
cellular respiration - carries a pair of electrons
NADPH - ANSWER✔ An electron carrier involved in photosynthesis. Light drives electrons from
chlorophyll to NADP+, forming NADPH, which provides the high-energy electrons for the reduction of
carbon dioxide to sugar in the Calvin cycle.
-carries a pair of electrons
FADH2 - ANSWER✔ A molecule that stores energy for harvest by the electron transport chain.
-carries electron pairs
cytochrome C - ANSWER✔ Involved in energy transfer, it is a protein released from mitochondria
when cell is stressed.
-single electron carrier
(delta)G=-nF(delta)E - ANSWER✔ equation relating E and Gibb's free energy change
(delta)E=E(acceptor)-E(donor) - ANSWER✔ equation for determining change in electric potential for
electron carriers
chemiosmotic theory - ANSWER✔ e- transfer to the last acceptor (O2) generates a H+ gradient across
the inner mitochondrial membrane. This electrochemical gradient is used by the mitochondria to drive
ATP synthesis from ADP + Pi
electron transport chain - ANSWER✔ A sequence of electron carrier molecules (membrane proteins)
that shuttle electrons during the redox reactions that release energy used to make ATP.
,NADH dehydrogenase - ANSWER✔ Complex I of ETC, Transfers electrons from NADH to ubiquinone
and pumps 4 H+ into the inter-membrane space
ubiquinone - ANSWER✔ soluble electron transporter in the electron transport chain that connects
the first or second complex to the third
succinate dehydrogenase - ANSWER✔ Complex II of ETC transfers electrons from FADH2 to
ubiquinone is not coupled to a proton pump (the reason why FADH2 makes less ATP)
cytochrome c oxidoreductase - ANSWER✔ complex III of ETC, electrons transferred from ubiquinone
from complexes I and II to this complex to cytochrome C (each Cytochrome c carries only 1 electron)
pumps four H+ to inter-membrane space
cytochrome oxidase - ANSWER✔ complex IV of ETC, electrons transferred from cytochrome C to
oxygen, making water and pumps 2 protons to inter-membrane space
ATP synthase - ANSWER✔ Large protein that uses energy from H+ ions to bind ADP and a phosphate
group together to produce ATP relies on the proton motive force generated from ETC
oxidative phosphorylation - ANSWER✔ The production of ATP using energy derived from the redox
reactions of an electron transport chain; the third major stage of cellular respiration.
photosynthesis - ANSWER✔ Plants use the sun's energy to convert water and carbon dioxide into
sugars and energy
photosystems I and II - ANSWER✔ ___ work together to produce NADPH and ATP from the sun light
photosynthesis - ANSWER✔ in ___ NADPH and ATP are used to make triosephosphate, starch, and
sucrose (glucose + fructose) from CO2 (AKA carbon assimilation)
Z-scheme photosynthesis - ANSWER✔ an enzyme is used to lyse water producing oxygen, and
creating the electron source. The electrons enter the P680 complex in photosystem II (at a low energy)
, and sunlight excites the electrons to an excited state. Through subsequent electron transfers, the
electrons are lowered back to a low energy state in photosystem I (transferred by Cyt b6f complex), to
P700. The electrons are excited with sunlight again to a high-energy state. Through subsequent electron
transfers, losing energy, the electrons can enter a cyclic route or non-cyclic route.
Cyclic- electrons re-enter Cyt b6f complex and are transferred back to photosystem I
Non-cyclic route - electrons are transferred to NADP+ to make NADPH
Beta-oxidation of fatty acids - ANSWER✔ Fatty acids are activated and transported into the
mitochondria - this process occurs in the matrix
4 step process
1. Oxidize B-carbon (from CH2 to C=C)
2. Rearrangement with water (C=C to CHOH)
3. Further oxidation (CHOH to C=O)
4. Transfer of carbonyl to make thiol ester with CoA-SH
NADH and FADH2 enter ETC
EXAMPLE:
16C fatty acid chain can make 8 acetyl-CoA -> TCA
NADH dehydrogenase - ANSWER✔ NADH from B-oxidation of fatty acids go to this complex for ETC
EFT:Q Oxidoreductase - ANSWER✔ inside the matrix it accepts FADH2 from B-oxidation of fatty acids
and transfers them to ubiquinone
fatty acid synthesis - ANSWER✔ starts with malonyl CoA + acetyl CoA catalyzed by fatty acid synthase
STEPS
1. Condensation reaction w/ loss of CO2
ANSWERS|RATED AND GRADED A+ NEW UPDATE| 2026/2027
NADH - ANSWER✔ the reduced form of NAD+; an electron-carrying molecule that functions in
cellular respiration - carries a pair of electrons
NADPH - ANSWER✔ An electron carrier involved in photosynthesis. Light drives electrons from
chlorophyll to NADP+, forming NADPH, which provides the high-energy electrons for the reduction of
carbon dioxide to sugar in the Calvin cycle.
-carries a pair of electrons
FADH2 - ANSWER✔ A molecule that stores energy for harvest by the electron transport chain.
-carries electron pairs
cytochrome C - ANSWER✔ Involved in energy transfer, it is a protein released from mitochondria
when cell is stressed.
-single electron carrier
(delta)G=-nF(delta)E - ANSWER✔ equation relating E and Gibb's free energy change
(delta)E=E(acceptor)-E(donor) - ANSWER✔ equation for determining change in electric potential for
electron carriers
chemiosmotic theory - ANSWER✔ e- transfer to the last acceptor (O2) generates a H+ gradient across
the inner mitochondrial membrane. This electrochemical gradient is used by the mitochondria to drive
ATP synthesis from ADP + Pi
electron transport chain - ANSWER✔ A sequence of electron carrier molecules (membrane proteins)
that shuttle electrons during the redox reactions that release energy used to make ATP.
,NADH dehydrogenase - ANSWER✔ Complex I of ETC, Transfers electrons from NADH to ubiquinone
and pumps 4 H+ into the inter-membrane space
ubiquinone - ANSWER✔ soluble electron transporter in the electron transport chain that connects
the first or second complex to the third
succinate dehydrogenase - ANSWER✔ Complex II of ETC transfers electrons from FADH2 to
ubiquinone is not coupled to a proton pump (the reason why FADH2 makes less ATP)
cytochrome c oxidoreductase - ANSWER✔ complex III of ETC, electrons transferred from ubiquinone
from complexes I and II to this complex to cytochrome C (each Cytochrome c carries only 1 electron)
pumps four H+ to inter-membrane space
cytochrome oxidase - ANSWER✔ complex IV of ETC, electrons transferred from cytochrome C to
oxygen, making water and pumps 2 protons to inter-membrane space
ATP synthase - ANSWER✔ Large protein that uses energy from H+ ions to bind ADP and a phosphate
group together to produce ATP relies on the proton motive force generated from ETC
oxidative phosphorylation - ANSWER✔ The production of ATP using energy derived from the redox
reactions of an electron transport chain; the third major stage of cellular respiration.
photosynthesis - ANSWER✔ Plants use the sun's energy to convert water and carbon dioxide into
sugars and energy
photosystems I and II - ANSWER✔ ___ work together to produce NADPH and ATP from the sun light
photosynthesis - ANSWER✔ in ___ NADPH and ATP are used to make triosephosphate, starch, and
sucrose (glucose + fructose) from CO2 (AKA carbon assimilation)
Z-scheme photosynthesis - ANSWER✔ an enzyme is used to lyse water producing oxygen, and
creating the electron source. The electrons enter the P680 complex in photosystem II (at a low energy)
, and sunlight excites the electrons to an excited state. Through subsequent electron transfers, the
electrons are lowered back to a low energy state in photosystem I (transferred by Cyt b6f complex), to
P700. The electrons are excited with sunlight again to a high-energy state. Through subsequent electron
transfers, losing energy, the electrons can enter a cyclic route or non-cyclic route.
Cyclic- electrons re-enter Cyt b6f complex and are transferred back to photosystem I
Non-cyclic route - electrons are transferred to NADP+ to make NADPH
Beta-oxidation of fatty acids - ANSWER✔ Fatty acids are activated and transported into the
mitochondria - this process occurs in the matrix
4 step process
1. Oxidize B-carbon (from CH2 to C=C)
2. Rearrangement with water (C=C to CHOH)
3. Further oxidation (CHOH to C=O)
4. Transfer of carbonyl to make thiol ester with CoA-SH
NADH and FADH2 enter ETC
EXAMPLE:
16C fatty acid chain can make 8 acetyl-CoA -> TCA
NADH dehydrogenase - ANSWER✔ NADH from B-oxidation of fatty acids go to this complex for ETC
EFT:Q Oxidoreductase - ANSWER✔ inside the matrix it accepts FADH2 from B-oxidation of fatty acids
and transfers them to ubiquinone
fatty acid synthesis - ANSWER✔ starts with malonyl CoA + acetyl CoA catalyzed by fatty acid synthase
STEPS
1. Condensation reaction w/ loss of CO2
