Lab11Answers - Plant Science 1203L Laboratory 11 Plant...

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Plant Science 1203L Laboratory 11 - Plant Metabolism (Due 11-2-07) Name: Today’s lab is on plant metabolism. So possibly the best place to start out with is a definition of the term. Metabolism is the chemical and physical process continuously going on in living organisms and cells, consisting of anabolism and catabolism . Anabolism is the process by which food is changed into living tissue. Since plants are autotrophic (able to produce their own food) the definition of anabolism also covers the production of food through photosynthesis, something that animals are incapable of doing. We will be studying photosynthesis next lab. Catabolism is the process by which food is converted into energy and wastes of a simpler chemical composition. For this lab we will be concentrating on the catabolic form of metabolism. It is obvious that metabolism covers all the biochemistry that is occurring within plant cells. Consequently, we will only touch on the major catabolic pathways in the plant. These processes that provide energy are glycolysis, the krebs cycle (tricarboxylic cycle or citric acid cycle) and finally oxidative phosphorylation (terminal oxidation). Enzymes - Virtually all the steps in the metabolism that we will talk about are driven by these enzymes. Some steps in metabolism may require more than one substrate (compound) in order to accomplish it’s role as a catalyst. In energy producing catabolism certain compounds (co-factors) in addition to the substrate are 2 particularly important. These are ATP, ADP, NADH, NAD+, FADH and phosphate (P). ATP has been called the energy currency of the cell and is involved in numerous enzyme mediated reactions in the cell. Starch - is the carbohydrate storage compound we have seen numerous times during lab this semester. Before it can be used as a substrate for energy production it must be digested or broken down into its’ basic building blocks of simple sugars such as glucose. Again this process is also controlled by enzymes (amylase). Since starch is a storage food reserve for the corn embryo it must be broken down to free sugars which will provide energy to the embryo through catabolism of the sugars. As the starch grains are digested they will become smaller and stain less strongly with the iodine solution. Exercise 1. Examine microscope 1 and observe normal starch grains from corn that have been stained with iodine. Compare what you see under this microscope with that of microscope 2, which has starch grains from corn that has been germinated. Answer the following questions: Are more of the starch grains from the germinated corn smaller than those from the ungerminated corn? As the corn seed germinated it uses the stored starch (starch grains) as a source of food. Enzymes produced by the developing embryo start to break down the starch to free sugars. As the starch is digested the starch grains become smaller and loose the ability to be stained by iodine.
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Are some of the starch grains from germinated corn less stained than from the ungerminated corn?
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This note was uploaded on 04/29/2008 for the course PLSC 1203L taught by Professor Longer during the Spring '08 term at Arkansas.

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Lab11Answers - Plant Science 1203L Laboratory 11 Plant...

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