Biochemistry-Oxidative Phosphorylation Flashcards
Why is given in cyanide poisoning?
Nitrites induce methemoglobin synthesis, which is Hb with a 3+ Fe. Cyanide has a really high affinity for methemoglobin and binds it instead of the heme of cytochrome oxidase. Thiosulfates are also given which bind to cyanide so it can no longer bind cytochrome oxidase.
How do electrons move between complexes in oxidative phosphorylation?
Complex I (NADH Dehydrogenase) gives its electrons to Q. QH2 takes electrons to complex III (Cytochrome bc1). Complex III gives its electrons to Cyt C which takes them to complex IV (Cytochrome oxidase). Oxygen then accepts the electrons and to make H2O. Meanwhile, complex V (ATP synthase) is using the hydrogen gradient to create ATP.
Why do you need multiple protons to be transported across the mitochondrial membrane in oxidative phosphorylation?
On hydrogen contributes a free energy around -5 kcal/mol. You need around 11 kcal/mol to make ATP in cellular conditions.
When ATP is made in the mitochondrial matrix, when does it need a transporter as it heads toward the cytosol?
When it crosses the inner membrane. The outer membrane has pores through which it can freely diffuse. It is transported by the antiport ANT that pushes out ATP and pulls in an ADP
Besides solute transporters, what else is contained in the mitochondrial inner membrane?
ETC complexes
How do scientists figure you get 2.5 ATP for every NADH?
You pump 10H per NADH oxidized. It takes 4H to enter the matrix to create 1 ATP. 10/4 = 2.5 ATP/NADH
What is the only TCA enzyme that is not located in the mitochondrial membrane?
Succinate dehydrogense is complex II. It is located in the inner membrane.
Where does FADH2 from succinate dehydrogenase pass its electrons?
Q after complex I.
How are the complexes arranged in the inner membrane of the mitochondria?
In order of increasing affinity for oxygen.
What complexes have components from mitochondrial DNA?
I,III,IV and V
LHON (Leber Hereditary Optic Neuropathy)
Maternally inherited late-onset acute optic atrophy that causes sudden blindness. 90% of patients with LHON had mtDNA mutations in complex I that effect ability of electron movement from complex I to Q.
Why is there such a wide distribution of symptoms in LHON disease?
Mitochondrial mutations exhibit heteroplasmy. This means replicated mutated daughter cells are distributed heterogeneously and randomly throughout the cells.
Why are mutation rates so high in mitochondria?
Lots of radical oxygen species are produced with few enzymes that can take care of them.
What is this biopsy characteristic of?
Ragged red fibers characteristic of MERRF (Myoclonic Epilepsy and Ragged Red Fiber) or MELAS (Mitochondrial Encephalomyopathy, Lactic Acidosis, and Strokelike Episodes)
