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(Including: Primary/Secondary/Tertiary Metabolism, Redox Potential, Biological Oxidation, Oxidases, Cytochrome Oxidase)
Metabolic pathways essential for survival and growth of cells.
Includes:
Glycolysis
TCA cycle
Oxidative phosphorylation
Fatty acid oxidation
Amino acid metabolism
Purpose: Energy production + synthesis of basic cellular components.
Metabolic pathways that produce specialized compounds not essential for basic survival but important for adaptation.
Examples:
Porphyrins
Melanin
Ketone bodies
Neurotransmitters
Hormones
Purpose: Specialized physiologic functions.
Pathways that deal with xenobiotics, drugs, toxins, reactive metabolites.
Includes:
Cytochrome P450 system
Phase I detoxification (oxidation, reduction, hydrolysis)
Phase II detoxification (conjugation)
Antioxidant systems (GSH, catalase, SOD)
Redox potential is the tendency of a substance to:
Accept electrons (get reduced) → high positive E₀
Donate electrons (get oxidized) → negative E₀
Electrons flow from lower to higher redox potential in the ETC.
Used to arrange ETC components in order
Explains unidirectional electron flow
Helps understand poisoning (e.g., cyanide blocks cytochrome oxidase)
enzyme-mediated transfer of electrons from donors → acceptors, producing energy.
Removal of hydrogen atoms:
Enzymes: Dehydrogenases
Coenzymes: NAD⁺, NADP⁺, FAD, FMN
Two major pathways:
Use O₂ as electron acceptor
Do NOT incorporate oxygen into substrate
Produce H₂O₂ or H₂O
Examples:
Cytochrome oxidase
Xanthine oxidase
Monoamine oxidase (MAO)
Incorporate oxygen into substrate
Types:
Monooxygenases (mixed-function oxidases)
One atom → substrate
One atom → water
Dioxygenases
Both O atoms into substrate
Terminal enzyme of ETC → reduces O₂ → H₂O.
Purine degradation → xanthine → uric acid.
Degradation of neurotransmitters (dopamine, serotonin, noradrenaline).
Oxidizes L-amino acids → α-ketoacids + H₂O₂.
Oxidizes D-amino acids (peroxisomes).
Glucose → gluconic acid + H₂O₂.
Final enzyme of ETC
Accepts electrons from cytochrome c
Reduces molecular oxygen to water
Cytochromes a and a₃
Contains copper (Cu²⁺) centers
Responsible for majority of ATP production
Maintains proton gradient for ATP synthase
Cyanide
Carbon monoxide (CO)
Hydrogen sulfide (H₂S)
Azide
These inhibit Complex IV → stop electron flow → cellular hypoxia despite normal oxygen (histotoxic hypoxia).
Flavoproteins (FMN, FAD)
Iron–sulfur proteins
Ubiquinone (CoQ)
Cytochromes (b, c₁, c, a, a₃)
Copper centers (in Complex IV)
Electron flow always proceeds from:
More negative → more positive redox potential
NADH → CoQ
Pumps protons
Contains FMN and Fe-S
FADH₂ → CoQ
Does NOT pump protons
Mobile carrier between complexes I/II → III
Accepts electrons + protons
Transfers electrons to cytochrome c
Fe-S + cytochromes b/c₁
Mobile, water-soluble carrier
Transfers electrons to Complex IV
Transfers electrons to O₂ → H₂O
Pumps protons
Uses proton gradient → synthesizes ATP
3 ATP per NADH; 2 ATP per FADH₂ (classic values)
Cyanide poisoning: inhibits Complex IV → rapid cellular asphyxia
CO poisoning: binds cytochrome oxidase + hemoglobin
Dinitrophenol (DNP): uncoupler → dissipates proton gradient → heat production
Barbiturates/Rotenone: inhibit Complex I
Antimycin A: inhibits Complex III
Oligomycin: inhibits ATP synthase (Complex V)
ETC occurs in inner mitochondrial membrane.
Electrons flow from NADH/FADH₂ → O₂ based on redox potential.
Complex IV = Cytochrome oxidase, inhibited by cyanide/CO.
Oxidases use O₂ as electron acceptor; may form H₂O₂.
Primary metabolism = essential pathways; secondary = specialized; tertiary = detoxification.
ATP synthesis requires intact proton gradient.
CoQ and cytochrome c are mobile carriers.
Enzymes that remove hydrogen atoms (2H: 2e⁻ + 2H⁺) from substrates and pass electrons to coenzymes like NAD⁺ or FAD.
Key in biological oxidation
Present in glycolysis, TCA cycle, β-oxidation, amino acid metabolism
Usually located in mitochondria (except cytosolic dehydrogenases like LDH)
Lactate dehydrogenase (LDH): Lactate ↔ pyruvate
Malate dehydrogenase: Malate → OAA (NADH)
Isocitrate dehydrogenase: Rate-limiting in TCA
Glucose-6-phosphate dehydrogenase (G6PD): Generates NADPH
Alcohol dehydrogenase: Alcohol → acetaldehyde
Succinate dehydrogenase: Succinate → fumarate (FADH₂)
Mobile electron carrier
Accepts 2 electrons + 1 proton → NADH
Participates mainly in catabolic, energy-producing pathways
Glycolysis (G3P-DH)
PDH complex
TCA cycle
β-oxidation
Ethanol metabolism
Lactate ↔ pyruvate
1 NADH → 3 ATP (classic) or 2.5 ATP (modern value)
Accepts 2 electrons + 2 protons → FADH₂
Bound tightly to enzymes (prosthetic group)
Succinate dehydrogenase (Complex II)
Acyl-CoA dehydrogenase (first step of β-oxidation)
PDH/α-KGDH complexes (via FAD-dependent E3 unit)
1 FADH₂ → 2 ATP (classic) or 1.5 ATP (modern)
Electron-carrying proteins with heme iron that cycles between:
Fe²⁺ (reduced)
Fe³⁺ (oxidized)
Electron Transport Chain (ETC)
Cytochrome b (Complex III)
Cytochrome c₁ (Complex III)
Cytochrome c (mobile carrier)
Cytochrome a / a₃ (Complex IV)
Carry single electrons; arranged by redox potential from lower → higher.
Enzymes that incorporate molecular oxygen into substrates.
Insert one atom of O₂ into substrate
Other atom → H₂O
Require NADPH + cytochrome P450
Role: Drug metabolism, steroid synthesis
Examples:
Cytochrome P450 enzymes, tryptophan hydroxylase
Insert both oxygen atoms into substrate
Examples:
Prolyl hydroxylase
Tyrosine hydroxylase
Tryptophan pyrrolase
Molecules releasing large amounts of free energy (ΔG° highly negative) upon hydrolysis.
Universal energy currency
ΔG° ≈ –7.3 kcal/mol
Highest high-energy phosphate: –14.8 kcal/mol
Energy reservoir in muscle
Used for rapid ATP regeneration
High-energy thioester bond
Generates GTP in TCA cycle
High-energy thioester used in multiple pathways
High-energy substrate of urea cycle/pyrimidine synthesis
High-energy sugar for glycogen synthesis
ETC is arranged in the inner mitochondrial membrane in four large complexes + two mobile carriers.
NADH → FMN → Fe-S → CoQ
Pumps protons (H⁺)
FADH₂ → Fe-S → CoQ
Does NOT pump protons
Mobile lipid-soluble carrier
Collects electrons from Complex I & II
Delivers to Complex III
Fe-S + cytochromes b & c₁
Transfers electrons to cytochrome c
Pumps protons
Small, water-soluble mobile protein
Transfers electrons to Complex IV
Cytochromes a & a₃ + copper centers
Reduces O₂ → H₂O
Pumps protons
Inhibited by: cyanide, CO, azide, H₂S
Uses proton gradient (proton motive force) to make ATP
Rotational motor (F₀) + catalytic head (F₁)
Electrons always flow from:
NADH → FMN → Fe-S → CoQ → Cyt b → Cyt c₁ → Cyt c → Cyt a → Cyt a₃ → O₂
Because redox potential increases stepwise.
| Complex | Proton Pumping | Energy Yield |
|---|---|---|
| I | Yes | NADH → ETC |
| II | No | FADH₂ → ETC |
| III | Yes | Contributes to PMF |
| IV | Yes | Final step to oxygen |
Complex V is NOT a pump—it uses the gradient.
Cytosolic NADH cannot cross the inner mitochondrial membrane.
Yet NADH from glycolysis must transfer its electrons into the mitochondria for ATP production.
Two biochemical shuttles carry reducing equivalents, not NADH itself:
Malate–Aspartate shuttle (high-efficiency, produces 3 ATP/NADH classic, 2.5 modern)
Glycerol-3-phosphate shuttle (lower efficiency, produces 2 ATP/NADH classic, 1.5 modern)
Location: Liver, heart, kidney
Efficiency: Highest (yields full NADH ATP)
Enzyme: Malate dehydrogenase (cytosolic)
Malate carries electrons across membrane.
Enzyme: Mitochondrial malate dehydrogenase
NAD⁺ → NADH formed inside mitochondria (full ATP yield).
Enzyme: Aspartate transaminase (AST)
Shuttle completes.
Each cytosolic NADH → equivalent mitochondrial NADH
→ generates 3 ATP (classic) or ~2.5 ATP (modern).
(Not asked often but needed for contrast)
Found in brain & skeletal muscle.
Cytosolic NADH converts DHAP → glycerol-3-phosphate.
Mitochondrial FAD is reduced → FADH₂ → Complex II
Produces less ATP because electrons enter ETC later.
Electrons move from low → high redox potential, finally reducing O₂ → H₂O.
NADH → Complex I (FMN, Fe-S) → CoQ → Complex III (cyt b, c₁) →
Cytochrome c → Complex IV (cyt a, a₃ + Cu²⁺) → O₂
FADH₂ (Complex II) → Fe-S → CoQ → Complex III → Complex IV → O₂
(No proton pump at Complex II → lower ATP yield)
Complex I
Complex III
Complex IV
Complex II does NOT pump protons.
Couples:
Electron transport through ETC
with
ATP synthesis by ATP synthase (Complex V)
Done via chemiosmotic mechanism.
Electron flow → pumps protons into intermembrane space →
creates proton motive force (PMF) consisting of:
Electrical gradient (Δψ)
Chemical gradient (ΔpH)
Protons return via ATP synthase, generating ATP.
F₀: Membrane channel that allows proton entry
F₁: Catalytic unit that synthesizes ATP
Three sites rotate between:
Loose (bind ADP + Pi)
Tight (form ATP)
Open (release ATP)
This rotation is driven by proton flow.
| Molecule | Classic ATP Yield | Modern P/O Ratio |
|---|---|---|
| NADH | 3 ATP | ~2.5 ATP |
| FADH₂ | 2 ATP | ~1.5 ATP |
Rotenone
Barbiturates
Piericidin A
Malonate
Antimycin A
Cyanide
Carbon monoxide
Azide
H₂S
Oligomycin
DNP
Thermogenin (brown fat)
High-dose aspirin
Cyanide → immediate inhibition of Complex IV → cellular hypoxia.
DNP → collapses proton gradient → hyperthermia.
Oligomycin → Stops ATP synthesis, electron flow also stops.
Aspartate aminotransferase is essential for malate shuttle.
Glycerol-3-phosphate shuttle is active during brain activity & fasting.
Electron transport through the ETC pumps protons (H⁺) from the mitochondrial matrix → intermembrane space.
This creates a proton motive force (PMF) made of:
Electrochemical gradient (charge difference)
pH gradient (H⁺ concentration difference)
ATP synthase uses this proton gradient to synthesize ATP.
This coupling of:
Oxidation (ETC)
with
Phosphorylation (ATP formation)
is called oxidative phosphorylation.
ETC complexes I, III, IV act as proton pumps.
Inner mitochondrial membrane is impermeable to H⁺.
Proton return through ATP synthase (Complex V) drives ATP formation.
Proton flow causes a rotational change in ATP synthase → mechanical → chemical energy conversion.
Any disruption of gradient = ATP synthesis stops.
Mitochondrial enzyme that converts proton flow → ATP.
Forms the proton channel.
Rotation of F₀ drives movement of catalytic sites.
Catalyzes: ADP + Pi → ATP
Has 3 catalytic β-subunits.
Each β-subunit cycles through:
Loose state → binds ADP + Pi
Tight state → synthesizes ATP
Open state → releases ATP
Rotational catalysis is driven by H⁺ moving through F₀.
Blocks F₀ proton channel.
Prevents proton entry → ATP synthesis stops.
Electron transport ALSO stops because gradient becomes too high.
Inhibits ADP/ATP translocase (ANT transporter).
Prevents entry of ADP → ATP synthesis halts.
Bind F₀ subunit → block proton flow.
Inhibiting ATP synthase blocks both phosphorylation AND electron transport.
Uncouplers allow protons to leak back into matrix WITHOUT passing through ATP synthase.
Result:
No ATP formation
Electron transport continues at full speed
Energy released as heat
Lipid-soluble proton carrier
Causes hyperthermia
Previously used as a weight-loss drug (dangerous)
Natural uncoupler in brown adipose tissue
Generates non-shivering thermogenesis in infants
Cause hyperventilation + metabolic acidosis
Increase heat production
Lab uncoupler
Strong protonophore
ETC speeds up
Oxygen consumption increases
ATP production ↓
Heat ↑
NADH/FADH₂ oxidized faster
Ionophores are compounds that transport ions across membranes, collapsing gradients.
Used widely in research; some seen in poisoning.
Potassium ion (K⁺) carrier
Inserts into membranes → collapses K⁺ gradient
Example of mobile carrier ionophore
Exchanges K⁺ for H⁺
Affects proton gradient → indirectly uncouples ATP synthesis
Forms ion channels in membranes
Allows Na⁺, K⁺ to move freely → disrupts membrane potential
| Feature | Uncouplers | Ionophores |
|---|---|---|
| Primary action | Dissipate H⁺ gradient | Move ions (H⁺, K⁺, Na⁺) |
| Effect on ETC | ETC continues fast | ETC may slow or collapse depending on ion |
| Effect on ATP | ATP synthesis ↓ | ATP synthesis ↓ |
| Example | DNP, thermogenin | Valinomycin, nigericin |
Chemiosmotic theory links electron flow → proton gradient → ATP synthesis.
ATP synthase has F₀ channel + F₁ catalytic head.
Oligomycin blocks ATP synthase (F₀).
DNP uncouples ETC from ATP formation; heat ↑.
Thermogenin physiologic uncoupler in brown fat.
Ionophores move ions across membranes (valinomycin = K⁺ carrier).
Proton gradient is essential for ATP generation.
ETC pumps H⁺ ions from mitochondrial matrix → intermembrane space.
Creates proton motive force (PMF): electrical + chemical gradient.
Proton gradient drives ATP synthase.
Inner mitochondrial membrane is impermeable to H⁺.
Any substance that collapses H⁺ gradient stops ATP synthesis.
Proton pumping occurs only at Complex I, III, IV.
Composed of F₀ (proton channel) + F₁ (ATP-forming head).
Works by rotational catalysis (binding change mechanism).
β-subunits go through Loose → Tight → Open states.
Uses energy of proton flow to convert ADP + Pi → ATP.
Blocked by oligomycin (F₀ inhibitor).
Most ATP of the cell comes from oxidative phosphorylation, not substrate-level phosphorylation.
Oligomycin blocks F₀ → no H⁺ flow → no ATP.
Atractyloside inhibits ADP/ATP translocase (ANT).
Venturicidin, DCCD directly block proton channel.
Inhibition of ATP synthase also stops ETC due to back-pressure of proton gradient.
Allow H⁺ to leak back into matrix without passing through ATP synthase.
Oxidation continues, ATP formation stops, heat increases.
DNP: toxic drug uncoupler → hyperthermia.
Thermogenin (UCP-1): physiologic uncoupler in brown fat → heat generation in infants.
Aspirin overdose acts as an uncoupler → metabolic acidosis + fever.
Uncouplers ↓ ATP, ↑ O₂ consumption, ↑ heat.
Lipid-soluble molecules that move ions across membranes.
Collapse electrochemical gradients → inhibit ATP synthesis.
Valinomycin → carries K⁺ across membrane.
Nigericin → exchanges H⁺ with K⁺ → affects proton gradient.
Gramicidin → forms ion channels for Na⁺/K⁺.
Ionophores differ from uncouplers:
Uncouplers move H⁺ only;
Ionophores move other ions too (K⁺, Na⁺, etc.), collapsing membrane potential.
Electrons flow from low → high redox potential.
Order: NADH → Complex I → CoQ → Complex III → Cyt c → Complex IV → O₂.
Complex II (succinate dehydrogenase) does NOT pump protons.
Oxygen is the final electron acceptor → forms water.
CoQ (ubiquinone) & cytochrome c are mobile electron carriers.
NADH → 3 ATP (classic), ~2.5 ATP (modern).
FADH₂ → 2 ATP (classic), ~1.5 ATP (modern).
ATP synthesis requires intact proton gradient.
Cyanide, CO, H₂S inhibit cytochrome oxidase (Complex IV) → cellular hypoxia.
Rotenone/Barbiturates inhibit Complex I.
Antimycin A inhibits Complex III.
Oligomycin blocks ATP synthase (F₀).
DNP uncouples → dangerous hyperthermia.
Brown fat activity (thermogenin) helps heat production in newborns.
A 28-year-old man is brought unconscious after inhaling fumes from burning plastic. He has severe lactic acidosis and normal oxygen saturation.
Acute cyanide poisoning.
Cyanide inhibits Complex IV (cytochrome oxidase).
ETC stops → no proton gradient → no ATP.
Cells shift to anaerobic glycolysis → lactic acidosis.
A newborn cannot maintain body temperature despite warm environment. Brown fat biopsy shows absence of UCP-1.
Defective thermogenin (UCP-1).
UCP-1 is a physiologic uncoupler.
No heat production → impaired non-shivering thermogenesis.
After taking “fat-burning pills,” an athlete develops high fever, tachycardia, and acidosis. The pills contain DNP (dinitrophenol).
DNP-induced uncoupling.
DNP carries H⁺ across membrane → no ATP synthesis.
ETC runs uncontrollably → heat production ↑↑.
Patient develops hyperthermia.
A patient with liver failure shows accumulation of NADH in mitochondria and inability to regenerate NAD⁺.
Failure of Malate–Aspartate Shuttle.
Without shuttle, cytosolic NADH from glycolysis cannot enter mitochondria.
ATP production falls sharply → lactic acidosis develops.
A farmer ingests a pesticide containing oligomycin. He develops muscle weakness and metabolic crisis.
Inhibition of ATP synthase (Complex V).
Oligomycin blocks F₀ proton channel.
Stops proton flow → no ATP synthesis.
ETC also stops because proton gradient becomes too steep.
A 5-year-old boy ingests high-dose aspirin. He has fever, hyperventilation, and metabolic acidosis.
Salicylate-induced uncoupling of oxidative phosphorylation.
High-dose aspirin acts as a weak uncoupler.
ETC continues but ATP drops → heat ↑ → respiratory alkalosis followed by acidosis.
A factory worker exposed to CO collapses. His PaO₂ is normal but tissues are hypoxic.
Carbon monoxide poisoning
CO binds cytochrome oxidase and hemoglobin.
ETC blockade → ATP stops → cellular hypoxia.
Biopsy shows swollen mitochondria and collapsed membrane potential due to a compound that increased K⁺ permeability.
Poisoning by valinomycin (ionophore).
Carries K⁺ across membrane → collapses electric gradient.
ATP synthesis impaired due to loss of membrane potential.
A farmer exposed to insecticide presents with weakness and lactic acidosis.
Complex I inhibition by rotenone.
NADH cannot transfer electrons to ETC.
NAD⁺ unavailable for glycolysis → lactate ↑.
Muscle biopsy shows normal Complex I–IV but defective ADP/ATP translocase (ANT).
Atractyloside-type inhibition.
ADP cannot enter mitochondria → ATP cannot be formed.
ATP remains trapped inside matrix; cytosol suffers deficiency.
A critically ill patient with sepsis has very high O₂ consumption yet low ATP levels.
Uncoupling due to mitochondrial damage.
ETC works rapidly but proton gradient is lost.
ATP synthase cannot function → ATP drops.
Lab worker exposed to FCCP complains of heat intolerance and muscle fatigue.
Exposure to a potent synthetic uncoupler.
FCCP transports protons directly → collapses gradient.
ATP production stops → heat ↑.
Biochemistry shows large buildup of pyruvate and lactate but normal oxygen.
Failure of glycerol-3-phosphate shuttle (less efficient NADH transfer).
Cytosolic NADH cannot be oxidized.
Converts pyruvate → lactate.
After consuming an antibiotic-contaminated food, a man presents with massive cellular swelling.
Gramicidin poisoning
Gramicidin forms membrane ion channels → Na⁺/K⁺ freely diffuse.
Membrane potential collapses → ATP production stops.
Brown adipose biopsy shows excessive UCP-1 activity.
Overactive thermogenin (UCP-1).
Excessive uncoupling → extreme heat production.
Energy lost as heat → weight loss.
A. Complex II
B. Complex V
C. Complex III
D. ADP/ATP translocase
Answer: C
A. Cytochrome c
B. Coenzyme Q
C. Oxygen
D. NAD⁺
Answer: C
A. Substrate-level phosphorylation
B. High-energy intermediates
C. Proton gradient across inner mitochondrial membrane
D. Electron carriers directly phosphorylating ADP
Answer: C
A. Complex I
B. Complex III
C. ATP synthase (Complex V)
D. Coenzyme Q oxidoreductase
Answer: C
A. FADH₂
B. DHAP
C. Mitochondrial NADH
D. ATP directly
Answer: C
A. Inhibition of Complex I
B. Increase in ATP
C. Decrease in oxygen consumption
D. Uncoupling of oxidative phosphorylation
Answer: D
A. Liver
B. Kidney
C. Brown adipose tissue
D. Heart
Answer: C
A. Glycerol-3-phosphate shuttle
B. Malate–aspartate shuttle
C. Carnitine shuttle
D. Citrate shuttle
Answer: B
A. Cytochrome b
B. Complex II
C. Cytochrome c
D. Complex IV
Answer: C
A. Complex II
B. Complex III
C. Complex I
D. Complex IV
Answer: C
A. Oligomycin
B. DNP
C. Atractyloside
D. FCCP
Answer: C
A. Complex I
B. Complex II
C. Complex III
D. Complex IV
Answer: D
A. ATP synthesis
B. Proton pumping by Complex V
C. Electron transport
D. Maintenance of membrane potential
Answer: C
A. NADH oxidase
B. Rotating catalytic head
C. Proton channel
D. Antiporter
Answer: C
A. H⁺
B. Na⁺
C. Ca²⁺
D. K⁺
Answer: D
A. Carnitine shuttle
B. Malate-aspartate shuttle
C. Glycerol-3-phosphate shuttle
D. Citrate shuttle
Answer: C
A. Increased ATP
B. Cellular hypoxia with normal PaO₂
C. Increased NADH
D. Increased oxidative phosphorylation
Answer: B
A. Complex I
B. Complex III
C. Complex IV
D. Complex II
Answer: D
A. NADH
B. FADH₂
C. Rotation of ATP synthase (F₀–F₁)
D. Cytochrome c
Answer: C
A. NAD⁺
B. FAD (Complex II)
C. Cytochrome c
D. FMN
Answer: B
A. Blocking ATP synthase
B. Blocking electron transport
C. Collapsing ion gradients
D. Inhibiting CoQ
Answer: C
A. ATP
B. NADH
C. Heat production
D. Proton gradient
Answer: C
A. Na⁺/K⁺ gradient
B. FAD/FADH₂ ratio
C. ΔpH + Δelectrical gradient
D. ATP/ADP ratio
Answer: C
A. Complex I
B. Complex II
C. Complex III
D. Complex IV
Answer: D
A. Valinomycin
B. Thermogenin (UCP-1)
C. Atractyloside
D. Oligomycin
Answer: B
Electron transport pumps protons to create a proton gradient, and ATP is synthesized when protons flow back through ATP synthase.
Across the inner mitochondrial membrane.
Complex I, III, and IV.
Complex II (Succinate dehydrogenase).
The combination of electrical and chemical (pH) gradient across the inner membrane.
Uses PMF to convert ADP + Pi → ATP.
F₀ (proton channel) and F₁ (catalytic head).
Protons enter and drive rotation of the enzyme.
ATP is synthesized by the β-subunits.
Loose → Tight → Open.
Oligomycin.
The F₀ proton channel, stopping proton entry.
Compounds that allow protons to leak back into the matrix without ATP synthesis.
DNP, thermogenin (UCP-1).
Thermogenin in brown fat.
ATP falls, heat production increases, ETC speeds up.
Lipid-soluble molecules that transport ions across membranes, collapsing gradients.
Valinomycin.
Gramicidin.
Exchanges H⁺ for K⁺.
Oxygen, reduced to water.
Complex IV (Cytochrome oxidase).
Complex I.
Complex II.
NADH → Complex I → CoQ → Complex III → Cyt c → Complex IV → O₂.
Tendency of a molecule to accept electrons (positive = strong oxidant).
Cytochrome c.
Coenzyme Q (Ubiquinone).
Malate–aspartate shuttle.
Glycerol-3-phosphate shuttle.
FADH₂.
Glycerol-3-phosphate shuttle.
Inhibitor of ADP/ATP translocase (ANT).
Inhibits Complex IV, stopping electron flow.
Inhibits Complex III.
Inhibits Complex I.
It is oxidized to NAD⁺ and donates electrons to ETC.
Water.
~2.5 ATP (modern value).
ETC stops because the proton gradient becomes too steep.
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