You already have much experience with the subject matter, biochemistry, in this chapter. Biology 115 (Principles of Biology) and Biology 221 (Cellular and Molecular Biology) are prerequisites for all your upper-division courses, so the subject in this chapter should be quite familiar to you. I will not be lecturing on this topic for more than a few minutes. You can expect exam questions to deal with this chapter in some way and you should be ready.
As you read this chapter, you might take special notice the plant-specific content. I will cite here just a few examples:
In Table 2.1 you might notice the greater importance of Magnesium in the list of important elements. Why would plants need this element in greater amounts than animals?I'll say this again: please be wary of errors in this book. It is a first edition so there are likely to be some problems that would not exist in a later edition. I promise I won't reiterate that again....On page 24 you find out that the cell wall is more than just cellulose. That might be a new idea for you. You begin to see the over-simplifications you have been taught in earlier courses...it tells you why science is more important than the facts generated by science.
On page 30 you learn something more about that special feature of plant cells: the cell wall. The complexity you are shown in Figure 2.8 helps you realize that this is not just some simple polymer. It also helps you begin to ask some questions (are you curious?). The structure shown here should lead you to ask about how a cell can grow with this kind of a woven structure...almost a basketweave...of a wall surrounding it.
On page 35 and suppporting text pages, note that not every vegetable oil is particularly good for folks with serum cholesterol levels that are above normal. Which advertising slogans on food packaging are most appealing to you now that you have read this section?
Plants make a wide range of molecules that are rarely appreciated until their uses are pointed out. Check out Table 2.2 on page 37. Our medicines would be limited and our food tasteless without plants.
Check out the polymer shown on page 40. This one is critical to your house standing upright, the chair holding your weight, etc. Lignin is probably the most-important least-appreciated polymer in biology. You may have never heard of it until now. It is what makes wood brittle. It can comprise 40% of some of our hardest woods. It determines wood strength, wood density, and of course its floatation capacity. It makes the walls of a fruit pit hard enough to prevent herbivory of the embryo inside the pit. At the cell level, it is a critical component of secondary cell walls.
First, the key word in the box of Jello at the store labeled "Pineapple Flavor" is "Flavor." An artificial flavoring agent (possibly) tricks (or at leasts suggests) your tastebud-brain connection to think "pineapple" when you taste that chemical. This has nothing to do with real pineapple in Jello.
Second, the gelled Jello containing real pineapple was made with canned pineapple. The natural protease (enzyme) in the real pineapple was irreversibly denatured by the heat treatment involved in the canning process. Thus while there is much Jello with canned pineapple around, you have never had Jello with fresh pineapple in it.
Now, can you explain the Jello made with pineapple juice? The answer is too obvious...ask me if you are not sure about it.
Would it make a difference if the juice container read "From Concentrate"?
Finally, could you make stiff Jello using frozen-pineapple chunks? Why? Why not?
Thinking along these lines might exercise your skills as a scientist. How would you conduct an experiment (a true one) to determine the answers to the questions just above?
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