Dr. Paul Tabor
1. You have been introduced to the electron carriers in the membranous cristae of the mitochondrion. Using an incredibly interesting interactive web site called the Virtual Cell, you can zoom into the crista of the mitochondria and see the arrangement of electron carriers that composes the electron transport system (ETS) in the membrane! Beginning at the Virtual Cell web page follow these steps to travel through the cell to the ETS: Select ZOOM as the action and in the search box select MITOCHONDRIA. Then click on the cell image to get to the enlarged image. Select CUT as the action and in the search box select CRISTA. Click on the image to get the next image. Select TURN and check the HOTSPOTS box and select NOTHING in the search box. Click on the image to get the next image. You should see three figures in a red HOTSPOTS box. Select ZOOM as the action and NOTHING in the search box. Click on the image. Select CUT as the action and check the HOTSPOTS box and select NOTHING in the search box. Click on the HOTSPOTS box and now you have located the electron carriers within the membrane. With the HOTSPOTS box checked, you can find the identity of the four electron carriers. You began at the outside of the mitochondrion and moved in a focussed manner to a set of molecules organized in the crista.
The electron carriers regulate the energy release from the electrons that are passed down the system so ATP can be synthesized (at this site, look in the section "How are mitochondria organized to be powerhouses"). There are compounds that are not a part of the electron transport system but these compouds can compete for electrons from the electron carriers. These compounds are called artificial electron acceptors and if they accept electrons they will not pass them on to the next electron acceptor in the system.
Could an artificial electron acceptor kill cells because it interrupts ATP synthesis? Would they kill a whole organism? If so, is there any antidote for this respiratory poison?
If an artifical electron acceptor would change color when it accepted an electron (reduced = colorless, oxidized = colored), could we use a simple color change to measure the rate of respiration? Before you check other web pages, try to think of some applications where artificial electron acceptors would be useful to determine if respiration was occurring.
2. By carefully regulating the electron flow down the electron transport system the energy that is released is used by three complexes of molecules in the system to pump protons (H+) into the intermembrane space. If the protons become concentrated, doesn't that mean the intermembrane space will become acidic (follow the lecture outline at this site to section C "Generation of the Proton Gradient " to help you answer this question)? How much of a difference in pH can be created by the proton pumps in the cristae?
3. You already are aware that almost all organisms respire. That means that the through the evolutionary process of trial and error respiration should have become an efficient energy-yielding process. A calculation has been made that indicates that the cell's efficiency of converting glucose to ATP is 39% efficient . Is that good? What is the efficiency of converting wind power into electricity and solar energy into electrical energy using solar batteries?