Week 7 - Energy of organisms

Can humans function using anaerobic respiration? No

Are there any times when humans do rely on anerobic cellular respiration? Yes, muscle cells can use anaerobic respirations when they run out of oxygen. (that is, when they are using energy faster than oxygen can be provided.) However, don't try this with other cells in the body. The energy requirements of central nervous system neurons are so high that even a brief period of hypoxia (from stroke, stangulation, etc) and the subsequent lack of ATP will cause rapid cell death.(http://www.neuropathologyweb.org/chapter2/chapter2aHIE.html)

ATP's of fermentation is a net of 2 per glucose vs. 36 per glucose molecules for aerobic respiration. So aerobic respiration is 18 times more efficient. So yes eukaryotes have more energy available to them.

reptiles, fish, birds, and mammals all use the same aerobic respiration. They are all running on that 18 times more efficient system than yeast in a anerobic environment. So why are cold-blooded less active.  Well it is said that fish are cold-blooded. Who is surprised, since it must be hard to maintain temperature in a media with the heat capacity of water.   BUT the fastest fish, the tunas,  are somewhat "warm-blooded"(esp, their swimming muscles). So warm-bloods move faster????  You witnessed the effect in the yeast lab ( yes, even those prokaryotic, cold-non-blooded yeasts.)  In biological systems, for every 10 degrees in temperature, the rate of chemical reaction is doubled. That is, until you raise the temperature far enough that you denature the enzymes. As long as you do not denature the enzymes, you can get energy twice as fast by raising the temperature 10 degrees.(of course, this is dependent on being able to supply substrate and in this case oxygen fast enough to keep up with the reactions.)

 A small fraction of this speed is due to the kinetic energy of the molecules involved. A greater amount of the speed is that the "heat" overcomes some of the activation energy. So it is not surprising to see lizards out basking in the sunlight.

Don't try to raise your body temperature 10 degrees to get energy twice as fast however. Our enzymes are tuned to work at the constant temp around 98.5.