oxidative phosphorylation Flashcards
electron transport
Electrons generally fall in energy through the chain - from complexes I and II to complex IV
How many ATP’s made per electron pair passed through the chain?
e- transport chain yields 10 H+ pumped out per electron pair from NADH to oxygen
4 H+ flow back into matrix for each ATP molecule synthesised
10/4 = 2.5 for electrons entering as NADH
For electrons entering as succinate (FADH2), about 6 H+ pumped per electron pair to oxygen
6/4 = 1.5 for electrons entering as succinate
see powerpoint for
step, product, ATP yield per glucose and system table
see powerpoint for
inhibitors of electron transport
cyanide poisoning
The toxicity of cyanide is largely attributed to the cessation of aerobic cell metabolism.
Cyanide causes intracellular hypoxia by reversibly binding to the cytochrome oxidase a3 within the mitochondria.
Cytochrome oxidase a3 is necessary for the reduction of oxygen to water in the fourth complex of oxidative phosphorylation.
Binding of cyanide to the ferric ion in cytochrome oxidase a3 inhibits the terminal enzyme in the respiratory chain and halts electron transport and oxidative phosphorylation.
This downward cascade is fatal if not reversed!!
use in terrorism and murder
In 1995, a device was discovered in a restroom in the Kayabacho Tokyo subway station, consisting of bags of sodium cyanide and sulfuric acid with a remote controlled motor to rupture them in what was believed to be an attempt by the Aum Shinrikyo cult to produce toxic amounts of hydrogen cyanide gas. Aum Shinrikyo are a nice bunch who also manufactured large quantities of nerve gasses (sarin and VX) and have killed with sarin in Tokyo.
In 2003, Al Qaeda reportedly planned to release cyanide gas into the New York City Subway system. The attack was reportedly aborted because there would not be enough casualties!
Neil Heywood
“an internal Chinese report confirmed that Heywood died from potassium cyanide added to his drink”
The Tylenol murders were a series of poisoning deaths resulting from drug tampering in the Chicago area in 1982. The victims had all taken Tylenol-branded acetaminophen (paracetamol) capsules that had been laced with potassium cyanide. Seven people died in the original poisonings, with several more deaths in subsequent copycat crimes. Enough cyanide to kill in the small 500mg capsules.
Richard Leonard Kuklinski (April 11, 1935 – March 5, 2006) was an American contract killer known as “the iceman” who favoured cyanide as a means of killing.
Jonestown
“Jonestown” was the informal name for the Peoples Temple Agricultural Project formed by the Peoples Temple, an American religious organization under the leadership of Jim Jones, in Guyana.
On November 18, 1978, over 900 people died in the remote commune, at the nearby airstrip in Port Kaituma, and in Georgetown, the capital city.
A total of 909 Americans died in Jonestown, all but two from cyanide poisoning, in an event termed “revolutionary suicide” by Jones.
industrial source of cyanide
insecticides photographic solutions metal polishing materials jewelery cleaners acetonitrile electroplating materials synthetic products such as rayon, nylon, polyurethane foam, insulation and adhesive resins
natural sources of cyanide
seeds and fruit pits of Prunus species
environmental sources of cyanide
smoke inhalation in closed-space fires
latrogenic sources of cyanide
sodium nitroprusside infusion
sodium azide
Sodium azide is best known as the chemical found in automobile airbags and airplane escape CHUTES. An electrical charge triggered by automobile impact causes sodium azide to explode and convert to nitrogen gas inside the airbag/CHUTE.
Sodium azide is used as a chemical preservative in hospitals and laboratories. Accidents have occurred in these settings. In one case, sodium azide was poured into a drain, where it exploded and the toxic gas was inhaled.
Sodium azide is used in agriculture (farming) for pest control.
Sodium azide is also used in detonators and other explosives.
Azide inhibits cytochrome oxidase by binding irreversibly to the heme cofactor in a process similar to the action of carbon monoxide. Sodium azide particularly affects organs that undergo high rates of respiration, such as the heart and the brain, this is not, on the whole, a good thing.
how many protein complexes in the inner mitochondrial membrane are involved in electron transport?
four
what shuttles between protein complexes in electron transport?
A lipid soluble coenzyme (UQ, CoQ) and a water soluble protein (cytochrome c)
what do NADH and FADH2 do in electron transport?
release their high-energy electrons and hydrogens to specialized molecules called flavoproteins
what are flavoproteins
metal-containing ions and cytochromes found in the inner membrane (cristae) of the eukaryote mitochondrion.
what do the electrons do to NADH and FADH2 in electron transport?
Electrons reduce and oxidize these molecules as they pass from one to the next, releasing small amounts of energy.
lower energy electrons
are attracted to singlet oxygen brought into the mitochondrial matrix by diffusion.
what does Oxygen serves as in the process of complete aerobic respiration.
the final electron acceptor
what happens to the Hydrogens from NADH and FADH2
pumped outside the membrane and begin to accumulate, forming a concentration (proton) gradient.
what is the result of the hydrogens being pumped outside the membrane?
This lowers the pH and results in protonmotive force that serves to drive the hydrogen ions through protein channels called ATP synthase (ATPase) molecules.
what happens as the hydrogens pass through ATPase
the enzyme links inorganic phosphates present in the cytoplasm or mitochondrial matrix to ADP molecules.
what happens once the hydrogens are in the cytoplasm
each pair of hydrogens is bound to oxygen, forming water. The complete breakdown of sugar and production of new ATP in the using oxygen as the final electron and hydrogen acceptor is called oxidative phosphorylation.
