Objectives:

• Use the resources on the world wide web to investigate questions about how cells generate the energy they need.
• Take a topic that frequently generates a "ho-hum" response from students and raise the level of interest by exploring respiration in some different directions.

Approach:

• I have selected three topics about which I have been curious to find out more. For each topic I will pose a question that extends beyond the information presented in the text. I will offer you some URLs where you can investigate additional information on each topic. You can use CUT and PASTE to bring information, including graphics, back to this web page to include in your answers in addition to the writing that you do. You do not have to do the questions in order. As is common on the web, there is always more that you can find to investigate beyond the suggestions I am providing for you.

Dr. Paul Tabor

OK, here are the questions:

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 compounds 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 d