Oxidative Phosphorylation

Question 1

whats involved in electron transport

Answer 1

Four protein complexes in the inner mitochondrial membrane

Question 2

what shuttles between protein complexes

Answer 2

A lipid soluble coenzyme (UQ, CoQ) and a water soluble protein (cytochrome c)

Question 3

electrons generally..

Answer 3

fall in energy through the chain - from complexes I and II to complex IV

Question 4

• NADH and FADH2

Answer 4

FADH2 release their high-energy electrons and hydrogens to specialized molecules called flavoproteins, metal-containing ions and cytochromes found in the inner membrane (cristae) of the eukaryote mitochondrion.

Question 5

what do the elctrons do to these moelcules

Answer 5

• Electrons reduce and oxidize these molecules as they pass from one to the next, releasing small amounts of energy.

Question 6

the lower energy electrons

Answer 6

are attracted to singlet oxygen brought into the mitochondrial matrix by diffusion.
- Oxygen serves as the final electron acceptor in the process of complete aerobic respiration.

Question 7

the hydrogens

Answer 7

• Hydrogens from NADH and FADH2 are pumped outside the membrane and begin to accumulate, forming a concentration (proton) gradient.
• This lowers the pH and results in protonmotive force that serves to drive the hydrogen ions through protein channels called ATP synthase (ATPase) molecules.
• As hydrogens pass through ATPase, the enzyme links inorganic phosphates present in the cytoplasm or mitochondrial matrix to ADP molecules.
• Once 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.

Question 8

How many ATPs made per electron pair passed through the chain?

Answer 8

• 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

Question 9

step and product

Answer 9

look at ppt

Question 10

inhibitors of electron transport

Answer 10

look at ppt

Question 11

cyanide poisoning

Answer 11

• The toxicity of cyanide is largely attributed to the cessation of aerobic cell metabolism.

Question 12

cyanide causes what?

Answer 12

• 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!!

Question 13

use in terrorism and murder

Answer 13

• 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!
• And something more topical………………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” 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.

Question 14

sources of cyanide

Answer 14

look at ppt

Question 15

sodium azide

Answer 15

• 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.

Question 16

azide inhibits what?

Answer 16

• 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.