Week 8 Flashcards
Where is the majority of the energy in eukaryotes generated?
By mitochondria
Oxidation and reduction in terms of electron transfer
Oxidation refers to loss of electrons. Reduction refers to gain of electrons.
Main supply of electrons to reduce oxygen are supplied predominantly by what?
NADH
Oxidative phosphorylation
The process of reducing oxygen in mitochondria is called oxidative phosphorylation because oxidation of electrons is coupled to the phosphorylation of ADP to generate ATP.
Two major sources of acetyl CoA
- Fatty acid beta-oxidation
- Glycolysis
Fatty acid beta-oxidation
Breakdown of even-chained fatty acids. Generates acetyl CoA
Glycolysis
Breakdown of glucose (6 carbons) into pyruvate (3 carbons). Pyruvate dehydrogenase oxidizes pyruvate to generate acetyl CoA
What generates NADH?
NADH is generated from the TCA (citric acid) cycle.
Via what process do mitochondria carry out oxidative phosphorylation?
The electron transport chain.
Four major complexes involved in the electron transport chain (in order)
- NADH dehydrogenase
- Succinate dehydrogenase
- Cytochrome C reductase
- Cytochrome C oxidase
Role of Complex I
Complex I (NADH dehydrogenase) facilitates transfer of electrons from NADH to quinone (Q)
Role of Complex III
Complex III (cytochrome c reductase) allows for transfer of electrons from quinol to cytochrome C
What is the problem solved by the Q cycle?
Quinol carries 2 electrons but cytochrome c can only accept 1.
Role of Complex IV
Complex IV (cytochrome c oxidase) allows for transfer of electrons from cytochrome C to oxygen.
Which complex accounts for 90% of oxygen use in cells?
Complex IV. This makes aerobic life possible.
How do poisons such as cyanide and azide work?
Poisons cyanide and azide bind to heme irons in complex IV more strongly than oxygen
In which complex is oxygen reduced?
Complex 4 is where oxygen is reduced.
Need four electrons to give rise to 2 molecules of water.
What is the energy from the oxidation of NADH and FADH2 used for?
To pump protons into the intermembrane.
What generates ATP in the electron transport chain?
Electrochemical proton gradient is used by the ATP synthase (sometimes also referred to as Complex V) to generate ATP
How does MPP+ work?
- Chemical called MPP+ derived from a contaminant in synthetically made heroin is taken into dopamine neurons by the dopamine transporter, where it acts as a competitive inhibitor of Complex I in mitochondria
- Besides compromising ATP production, MPP+ also increase generation of free radicals (i.e., reactive oxygen species)
What role did MPP+ play in Parkinson’s Disease research?
Provided paradigm-shifting insight into Parkinson’s Disease by pinpointing mitochondrial dysfunction as the likely culprit
What’s so special about mitochondria using an electrochemical gradient to generate ATP?
Frees eukaryotic cells from the surface area: volume ratio constraint, allowing them to produce greater amount of ATP
Multiple lines of evidence support endosymbiotic origins of mitochondria
- Own genome
- Sensitivity of mitochondrial ribosomes to antibiotics
- Protein synthesis starts with N-formylmethionine like in bacteria
What did the Fzo experiment reveal?
Fuzzy onion (Fzo) mutant yeast cells have fragmented mitochondria compared to the wild type, suggesting impaired fusion. Concluded that the mutant was unable to undergo fusion.
