Oxidative Phosphorylation Flashcards
(22 cards)
What is meant by respiratory control?
Uptake of oxygen by mitochondria is controlled by components of ATP production, Pi and ADP
What is the purpose of respiratory control?
To match oxygen uptake to energy requirements
Give 5 examples of metabolic poisons
Malonate Cyanide Rotenone Dinitrophenol Oligomycin Azide (N3)
Mechanism of malonate
Structurally similar to succinate so it is a competitive inhibitor of succinate dehydrogenase. This slows down the flow of electrons from succinate to ubiquinone because it prevents the oxidation of succinate to fumarate.
Mechanism of cyanide
Binds with high affinity to the ferric (Fe3+) form of the haem group in the cytochrome oxidase complex. This blocks the flow of electrons through the respiratory chain and consequently the production of ATP halts.
What other metabolic poison works in a similar way to cyanide?
Azide
Mechanism of Rotenone
An isoflavone found in the roots and seeds of some plants. It blocks the transfer of electrons from complex I to ubiquinone
Mechanism of Oligomycin
An antibiotic produced by STreptomyces that blocks oxidative phosphorylation by binding to the stalk of ATP synthase and thereby preventing proton flow.
Mechanism of dinitrophenol
A proton ionopore which can shuttle protons across the inner mitochondrial membrane
What is oxidative phosphorylation?
The production of ATP using energy derived from the transfer of electrons in an electron transport chain
Outline the 2 basic steps of oxidative phosphorylation
1) Translocation of protons from mitochondrial matrix into the intermembrane space (facilitated by the ETC)
2) Pumped protons are allowed back into the mitochondria via a specific channel that is coupled to the enzyme ATP synthase
What does the ETC consist of?
2 carriers and 3 enzymes
What are these 2 carriers?
Cytochrome C Coenzyme Q (ubiquinone)- mobile
What are the 3 enzymes and where are they situated?
NADH dehydrogenase complex
Cytochrome b-c1 complex
Cytochrome oxidase complex
These are built into the structure of the inner mitochondrial membrane
What does NADH do?
It donates a hydride ion which is subsequently split into its constituent components, 2 electrons and a proton
What is the order of the electron transport chain?
Electrons donated from NADH to NADH dehydrogenase complex
Coenzyme Q (ubiquinone) next
Then Cytochrome b-c1
Then Cytochrome C
Finally electrons passed onto Cytochrome oxidase which catalyses the final reduction reaction involving oxygen
What happens as an electron passes through each protein?
A proton is pumped into the intermembrane space
How come the electrons flow in this order?
Flow from a carrier of higher reducing potential to one of lower reducing potential
i. e. low redox potential to high redox potential
i. e. low electron affinity to high electron affinity
What makes coenzyme Q mobile?
Long hydrophobic tail which makes it freely soluble and mobile in the non polar interior of the inner mitochondrial membrane
Final reduction reaction of cytochorme oxidase
O2 + 4e- + 4H+ -> 2H2O
ATP synthase is largely made of two main components which are
F0 = membrane bound component F1 = projection into matrix
Significance of OLT
a series of conformational changes that occur on the beta subunit as the axel of ATP synthase turns
O: site is open and nothing is bound to it
L: Conformational change converts the site into a low affinity state so that ADP and Pi loosely bind to the site.
T:Further conformational change further alters the affinity so that ADP and Pi now become tightly bound. This is now catalytically active and ATP is formed.
