LEHNINGER PRINCIPLES OF BIOCHEMISTRY
2026 STUDY GUIDE REVISION SHEET CORE
CONCEPT BREAKDOWN
◉ respiratory chain.
Answer: The electron-transfer chain; a sequence of electron-
carrying proteins that transfers electrons from substrates to
molecular oxygen in aerobic cells.
◉ flavoprotein.
Answer: An enzyme containing a flavin nucleotide as a tightly bound
prosthetic group.
◉ reducing equivalent.
Answer: A general term for an electron or an electron equivalent in
the form of a hydrogen atom or a hydride ion.
◉ ubiquinone (coenzyme Q, Q).
Answer: A mobile component of the mitochondrial electron
transport chain, where it acts as a pro-oxidant in its ubisemiquinone
state.
◉ cytochromes.
, Answer: Heme proteins serving as electron carriers in respiration,
photosynthesis, and other oxidation-reduction reactions.
◉ iron-sulfur protein.
Answer: One of a large family of electron-transfer proteins in which
the electron carrier is one or more iron ions associated with two or
more sulfur atoms of Cys residues or of inorganic sulfide.
◉ Rieske iron-sulfur protein.
Answer: A type of iron-sulfur protein in which two of the ligands to
the central iron ion are His side chains; act in many electron-transfer
sequences, including oxidative phosphorylation and
photophosphorylation.
◉ Complex I.
Answer: The first large protein complex of the respiratory chains of
myriad organisms from bacteria to humans. It catalyzes the transfer
of electrons from NADH to coenzyme Q₁₀ and translocates protons
across the inner mitochondrial membrane in eukaryotes or the
plasma membrane of bacteria. Also known as NADH dehydrogenase.
◉ NADH dehydrogenase.
Answer: The first large protein complex of the respiratory chains of
myriad organisms from bacteria to humans. It catalyzes the transfer
of electrons from NADH to coenzyme Q₁₀ and translocates protons
2026 STUDY GUIDE REVISION SHEET CORE
CONCEPT BREAKDOWN
◉ respiratory chain.
Answer: The electron-transfer chain; a sequence of electron-
carrying proteins that transfers electrons from substrates to
molecular oxygen in aerobic cells.
◉ flavoprotein.
Answer: An enzyme containing a flavin nucleotide as a tightly bound
prosthetic group.
◉ reducing equivalent.
Answer: A general term for an electron or an electron equivalent in
the form of a hydrogen atom or a hydride ion.
◉ ubiquinone (coenzyme Q, Q).
Answer: A mobile component of the mitochondrial electron
transport chain, where it acts as a pro-oxidant in its ubisemiquinone
state.
◉ cytochromes.
, Answer: Heme proteins serving as electron carriers in respiration,
photosynthesis, and other oxidation-reduction reactions.
◉ iron-sulfur protein.
Answer: One of a large family of electron-transfer proteins in which
the electron carrier is one or more iron ions associated with two or
more sulfur atoms of Cys residues or of inorganic sulfide.
◉ Rieske iron-sulfur protein.
Answer: A type of iron-sulfur protein in which two of the ligands to
the central iron ion are His side chains; act in many electron-transfer
sequences, including oxidative phosphorylation and
photophosphorylation.
◉ Complex I.
Answer: The first large protein complex of the respiratory chains of
myriad organisms from bacteria to humans. It catalyzes the transfer
of electrons from NADH to coenzyme Q₁₀ and translocates protons
across the inner mitochondrial membrane in eukaryotes or the
plasma membrane of bacteria. Also known as NADH dehydrogenase.
◉ NADH dehydrogenase.
Answer: The first large protein complex of the respiratory chains of
myriad organisms from bacteria to humans. It catalyzes the transfer
of electrons from NADH to coenzyme Q₁₀ and translocates protons
