MAC - Week 05 Lecture 3 - Oxidative phosphorylation and the electron transport chain_IT_ARP
Page 1: Overview of Oxidative Phosphorylation
Oxidative phosphorylation involves the electron transport chain (ETC) located in the mitochondrial inner membrane.
Key components in the process include hydrogen ions (H+), electron carriers, and various complexes (I-IV).
Process
H+ ions are pumped into the intermembrane space via the ETC, creating a gradient.
Electrons from NADH and FADH2 travel through the complexes to reduce oxygen, forming water.
Page 2: Learning Outcomes
Understand the generation of proton motive force in mitochondria.
Comprehend the functions of ETC complexes: I-IV, CoQ, and cytochrome c.
Learn the regulation of mitochondrial ATP synthase and implications of mitochondrial diseases.
Page 3: Glucose Metabolism Recap
Glucose is metabolized into pyruvate through glycolysis.
Pyruvate is converted to acetyl-CoA in mitochondria and enters the TCA cycle.
TCA cycle generates NADH and FADH2, which are essential for ATP production.
Page 4: Mitochondrial Compartment Structure
Main Functional Compartmentsi. Outer membraneii. Intermembrane spaceiii. Inner membraneiv. Cristaev. Matrix (central space)
Page 5: Mitochondrial Dynamics
Mitochondria are dynamic organelles, constantly fusing and dividing.
They form long and branched structures, varying in number per cell based on energy demands.
Page 6: Inner Membrane Characteristics
The inner membrane lacks porins, making it highly impermeable.
It contains cardiolipin, which enhances membrane stability, and is rich in proteins (76%), folded into cristae.
Page 7: Function of the Electron Transport Chain
The ETC (respiratory chain) converts energy from high-energy electrons in NADH and FADH2 into ATP.
This occurs through a series of four complexes (I-IV), facilitating electron transfer and proton pumping.
Page 8: Learning Outcomes Reiterated
Similar learning outcomes as listed on Page 2.
Page 9: Hydrogen Ion Gradient Creation
Water can dissociate into hydroxyl ions (OH-) and hydrogen ions (H+), impacting reactions.
Hydrogen ions are crucial as they represent protons that contribute to the electrochemical gradient.
Page 10: Hydrogen Ion Pumping
The ETC pumps H+ ions from the matrix to the intermembrane space via its four protein complexes.
Page 11: Generation of Proton Motive Force
Proton motive force (PMF) arises from the H+ concentration gradient and membrane voltage.
This results in a strong electrochemical potential, driving protons back into the matrix.
Page 12: ATP Generation Mechanism
ATP synthase uses PMF to convert ADP and inorganic phosphate (Pi) into ATP as H+ ions flow back into the matrix.
Page 13: Electron Pathway
Pathway of electrons: NADH -> Complex I -> CoQ -> Complex III -> Cyt c -> Complex IV -> O2.
Remember the sequence for better comprehension.
Page 14: Learning Outcomes Reiterated
Similar learning outcomes as listed on previous pages.
Page 15: Complex I: NADH Dehydrogenase
NADH donates electrons to complex I, which transfers them to Coenzyme Q (CoQ).
Simultaneously, complex I pumps 4 H+ ions from the matrix into the intermembrane space.
Page 16: Complex II: Succinate-CoQ Reductase
Complex II connects the TCA cycle to the ETC, converting succinate to fumarate and producing FADH2.
It does not pump protons directly but passes energy to CoQ.
Page 17: Complex III: CoQH2-Cytochrome C Reductase
Collects energy from CoQ, transferring electrons to cytochrome c while pumping 2 H+ ions out of the matrix.
Page 18: Complex IV: Cytochrome C Oxidase
Receives electrons from cytochrome c and transfers them to molecular oxygen, producing water and pumping another H+ into the intermembrane space.
Page 19: Coenzyme Q (CoQ)
Coenzyme Q diffuses in the inner mitochondrial membrane, accepting 2 electrons at a time and becoming CoQH2.
Page 20: Cytochrome c
A small, water-soluble protein that carries one electron at a time between the ETC complexes in the intermembrane space.
Page 21: Quiz Time
Page 22: Haem Groups in Electron Transport
Haem groups facilitate electron transport; the central iron atom can transition between Fe2+ and Fe3+.
They are composed of a common iron atom and porphyrin ring, each able to shuttle one electron.
Page 23: Iron-Sulfur Clusters
Iron-sulfur clusters in complexes II and III transport electrons using inorganic sulfur and cysteine-derived sulfur atoms.
They can only transfer one electron at a time.
Page 24: Overview of the Electron Transport Chain
Electrons from NADH and FADH2 travel through the electron transport chain complexes sequentially to provide energy for ATP synthesis.
Page 25: Identify Proteins Quiz
Page 26: ATP Synthase Structure
ATP synthase consists of two main subcomplexes (F0 and F1) crucial for ATP production.
Page 27: Proton Transit through ATP Synthase
The mechanism allows protons to transit through ATP synthase, facilitating ATP production through rotation.
Page 28: Rotation Mechanism of ATP Synthase
The γ and c units rotate to allow protons to pass, while the α and β units remain static, acting as a tightening mechanism.
Page 29: Proton-Induced Rotation
Protons affect the c unit of ATP synthase, causing rotation and facilitating ATP synthesis.
Page 30: ATP Synthesis Mechanism
The rotation of the γ subunit induces a squeezing action that phosphorylates ADP to produce ATP.
Page 31: ATP Production Summary
For each complete rotation of the γ unit, 3 ATP molecules are synthesized.
Page 32: ADP/ATP Antiporter Function
The antiporter shuttles synthesized ATP out of the matrix, allowing ADP and phosphate to enter for continuous ATP synthesis.
Page 33: PMF and ATP Export
The proton motive force drives the movement of OH- and charged ATP molecules through various transporters, ensuring a co-exchange process.
Page 34: Learning Outcomes Reiterated
Similar learning outcomes as listed on previous pages.
Page 35: Respiratory Control Mechanism
When ADP levels drop, ATP synthase halts, leading to an accumulation of H+ and a blockage of the ETC, thereby regulating energy production.
Page 36: Inhibitors of Electron Transport
Various inhibitors directly block the electron transport chain at specific complexes, affecting ATP synthesis:
Complex I - Rotenone
Complex II - Carboxin
Complex III - Antimycin
Complex IV - Cyanide, Azide, Carbon Monoxide
ATP Synthase - Oligomycin
Page 37: Uncouplers of Electron Transport
Uncouplers dissipate the proton gradient without directly blocking electron transport, leading to a 'leak' that reduces ATP synthesis.
Page 38: 2,4-Dinitrophenol as Uncoupler
Synthetic uncoupler that allows protons to cross the membrane, collapsing the H+ gradient and ceasing ATP synthesis.
Page 39: Thermogenin as Natural Uncoupler
Uncoupling protein that generates heat by allowing protons to return to the matrix without ATP synthesis, found in brown adipose tissue.
Page 40: Brown Fat in Babies
Babies have high brown fat deposits to maintain body temperature and counteract heat loss due to large surface area.
Page 41: Brown Fat in Adults
Some adults retain small amounts of brown fat, which can significantly increase caloric burn and aid in weight management.
Page 42: Quiz Time
Page 43: Mitochondrial Genetics Overview
Mitochondria require approximately 1,000 proteins to function, but only 13 are encoded by mitochondrial DNA - the rest by nuclear DNA.
Page 44: Mitochondrial Gene Transmission
Mitochondrial DNA is maternally inherited, showing non-Mendelian inheritance patterns affecting progeny.
Page 45: Nuclear Gene Contributions to ETC
Complexes I-IV contain proteins coded by nuclear DNA, displaying standard genetic inheritance alongside mitochondrial DNA.
Page 46: Learning Outcomes Reiterated
Similar learning outcomes as listed on previous pages.
Page 47: Mitochondrial Diseases
Genetic disorders linked to mitochondrial or nuclear DNA affecting mitochondrial function, presenting varied severity levels.
Page 48: Heteroplasmy in Egg Cells
Random mutations may result in egg cells with varying proportions of defective mitochondria, complicating inheritance.
Page 49: Origins of Mitochondrial Disease
Most mitochondrial diseases are inherited, with only 15% due to mitochondrial DNA mutations; the majority are nuclear gene-based.
Page 50: Symptoms of Mitochondrial Disease
Symptoms vary widely ranging from mild exercise intolerance to severe conditions like myopathy and neurodevelopmental disorders.
Page 51: Examples of Mitochondrial Diseases
Various diseases include mitochondrial myopathy, diabetes and deafness syndrome, neuropathy, and mtDNA depletion syndrome.
Page 52: Diagnosing Mitochondrial Diseases
Common diagnostic tests include Southern blot and PCR to identify mutations in muscle biopsy samples.
Page 53: Mitochondrial DNA Depletion Syndrome
A severe disorder reducing mitochondrial DNA levels, affecting muscle, liver, and brain function, often fatal in infancy.
Page 54: Genetic Testing Case Study
Charlie Gard’s condition was linked to mutations in the nuclear gene RRM2B, impairing DNA replication in mitochondria, affecting treatment options.
Page 55: Summary of Key Processes
H+ ions pumped by complexes I, III, and IV, and the electron pathway from NADH/FADH2 to oxygen producing ATP.
Page 56: Reading Recommendations
Alberts et al. "Essential Cell Biology" Chapter 14 (pages 453-476): Overview of oxidative phosphorylation.