This chapter is about energy...what an important topic for a study of life. A lot of people think of plants as having no energy because of their lack of locomotion. Of course it is through plants that essentially all biological energy enters the biosphere. The only exception that I know of are organisms using using the thermal energy of ocean floor vents and similar surface geothermal vents.
This chapter begins with the physico-chemical foundation of energy and thermodynamics. That may be difficult reading, but this chaper is mercifully superficial and will probably provide you with a nice foundation if you read it patiently.
The chapter continues with a section on enzymes. That should be a very familiar topic to you from Biology 115 (Principles of Biology) and Biology 221 (Cellular and Molecular Biology).
As before, when you read this chapter, you might take special notice of the following:
On page 101 under Free Energy and Chemical Equilibrium, a very important statement is made. Frequently biology books spend a lot of time talking about the concept of equilibrium. This is one of the first books that points out the obvious fact that the concept of equilibrium is not very important to life. In fact, equilibrium is antithetical to life, the laws of thermodynamics (particularly the second law) dictates that life exists on the basis of tremendous flow (not equilibrium).I am thrilled with the presentation about ATP on page 103. I cannot vouch for the accuracy of the numbers, but the point about 220 kg of ATP per day is certainly memorable. So many books talk about ATP as a molecule for ATP storage; a horrible mis-statement. If a human (weighing 70 kg) goes through 220 kg of ATP per day, you can obviously see that this cannot be a storage molecule. It is obviously turned over rapidly. The idea that only a few grams of ATP are present in the body gives you some idea of the rapidity of turnover and a clear notion that other molecules are the true energy storage molecules.
The caption of Fig 5.10 mentions that the heme group is outlined in green. My copy is outlined in blue, but I point this out not to point up mistakes, but to have you notice the main feature of heme that applies equally to chlorophyll. Both of these molecules have a large metal ion (Fe in cytochrome, Mg in chlorophyll) that is used to deal with electrons in electronic reactions. The outlining colors in the figure show you how the organic part of the cytochrome facilitates this. If you let your eye follow the colored lines around the iron atom, you should notice that every-other bond is shown as double. In reality the bonds surrounding the metal ion are resonant, meaning that the electrons in these bonds are shared among the bonds forming an electron cloud of sorts. This permits electrons going toward or coming from the metal ion to be more easily absorbed or given off. This feature of both cytochromes and chlorophyll explain how they work.
The section on enzymes is sketchy, but more details will be added later in the book.
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