1. Although the outer mitochondrial membrane is permeable to all small molecules

Question

1. Although the outer mitochondrial membrane is permeable to all small molecules, the inner mitochondrial membrane is essentially impermeable in the absence of specific transport proteins. Consider this information and what you have learned about the citric acid cycle to address the following questions. If the inner mitochondrial membrane were rendered as permeable as the outer membrane, how would that affect oxidative phosphorylation? Which specific processes would stop and which remain?

2. Cyanide has been used as a poison for thousands of years. The effects of high-dose cyanide are quick, and death can occur within minutes. One of the primary targets of cyanide is Cytochrome c oxidase (Complex IV in electron transport chain), where it acts an irreversible inhibitor and prevents the binding of oxygen.

Based on your knowledge of the electron transport chain and the inhibitor target described above, how might cyanide affect electrochemical gradient formation, and how might it lead to cell death

Explanation / Answer

Based on the given data,

1)

If the inner mitochondrial membrane were rendered as permeable as the outer membrane, then it leads to mitochondrial proton leaks. So, the proton motive force (PMF or p) would not generate for the production of synthesis of ATP by ATP synthase. Certain uncouplars and uncoupling proteins, like adenine nucleotide translocase in inner membrane are causes Proton leaks. The rate of oxygen consumption will increases in an exponential manner.     

Therefore, the ATP synthesis would stop.

However, the critic acid cycle (TCA) and beta-oxidation of fatty acids, etc cannot be affected by the Proton leak. These pathways produce reducing equivalents for the production of ATP.    

2)

Oxidative phosphorylation is the process of ATP production through electron transport chain. It is an aerobic metabolism and is brought by chemiosmosis mechanism. As shown in the process map, the process of oxidative phosphorylation involves the loss of electrons from NADH or FADH2.

Then they are carried by cytochromes through a series of transferases I-IV, releasing H+ ions (protons) in the process. When the protons re-enter the cell, they release the energy that allows ADP and phosphate to bind, producing ATP.

The potentially toxic chemicals identified based on their level of acute toxicity. In acute toxicity condition, a toxin instantly kills an organism within short span of time. The LD50 value of Sodium cyanide is 10.0 (mg/kg). Cyanide is known to block the flow of electrons from the ETC to oxygen. This leads to a halt in the electron transport chain. As a result of this, the process of chemiosmosis is stopped and the rate of ATP production declines.

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