Chemical Basis of Living Organisms
Instructor: Dr. Christina Jacobs
By Richard Matthews
E-portfolio Enduring Understanding Rubric Item:
Comprehension of Science / Chemistry Content Enduring Understandings
The enduring understanding that I have selected from this class to use as my evidence of growth is Course EU letter B
What the Evidence Is:
During a Biochemistry pre-class assignment, I attempted to discuss this EU. Dr. Jacobs inspired me with her comment that I was off to a good start, but looked forward to more examples as I progress through the course. Her comment will serve as my baseline evidence of where I began. In the next paragraph, as I state why I chose it, I will include the evidence that shows how I have grown.
Why I Chose It:
Course EU letter B was addressed early in the course and carried straight through to the end as the class was introduced to several other representations including functional groups so I chose this particular EU. As I recall in the first MISEP Chemistry 511 course, although doing Lewis dot (flat) drawings was a simple concept to grasp for me, the 3-dimentional representations were a little more challenging with the naming of the shape and the steric number formulas. I interpreted this EU as understanding, first, the Periodic Table and the symbols and positioning of each element. Next, electron configurations can help with the Lewis dot drawings to further aid in seeing the number of electrons associated with an atom. Finally, 3-D drawings allowed me to view the geometrical shape. See evidence of growth for chemical symbolism and ways of representing ideas as shown in my Wintergreen Ester Synthesis Chromatography lab paper (July 3rd).
How It Illustrates Growth:
The course began with a review of Lewis dot (flat) drawings, which quickly went to 3-dimentional representations. As you can see in my interpretation above, this is where I stopped. From the Lewis dot (flat) drawings, I was introduced to the condensed and structural formulas. Using the condensed formula, I learned to order them according to their electronegativities, which happen to be alphabetical order (C, H, N, O for most organic molecules). I learned that when writing a structural formula, atoms are listed in order according to their connectivity. Equivalent hydrogen bonds are grouped after the atom they are attached to. The next two representations are drawings that I would see often on the chalkboards in my first MISEP chemistry class (Dr. Tony Pietrovito). I would often wonder how one could distinguish what it was just based on how it was drawn. I knew that they had a way of identifying them, but it puzzled me. I now know how they are identified. Another representation is line structures. To help me understand line structures, I know that where there are intersecting lines there are carbon atoms as well as at the end of a line. Where there are carbon atoms there will most likely be hydrogen atoms. The Ester synthesis and Chromatography Lab showed my understanding of the various chemical symbols.
Near the end of course, to further understand chemical representations, the focus was shifted to protein structure and its function. Here, I learned the amino acid groups, which is the primary structure of the protein. What really helped me with identifying them was the homework sheet on amino acids. Here I had to color the side chains and the backbones two different colors. Continuing with the protein structure and its function, what helped me with the concepts of: secondary structure, tertiary structure, and quaternary structure were the interactive, virtual tours that was available to view and manipulate on the electronic blackboard. The Òball and stickÓ and CPK model helped me see the various bonds, while the ribbon and rocket models helped to see spiral direction.
Finally, what sticks with me the most concerning molecules being represented in many ways, is the discussions on how biologists and chemists interpret similar concepts with different drawings or illustrations. I recall in MISEP Biology, how a lot of the lectures were accompanied by cartoon renditions. One example used in class was how ATP is made. It showed a continuum, circular path, of ADP to ATP (within a yellow or sometimes a green sun burst) with exergonic and endergonic reactions. What diagrams like this fail to show is what happens in that yellow sun burst, at the molecular level. This was talked about in class. I also showed my understanding of this on the final quiz.
Chemical Representations, some general usefulness and
limitations
Depending on what one is looking for or learning, or whether you, a chemist or a biologist, there is a chemical representation for you. For biologists, some will need to look at things at the molecular level, while others just want to see what things look like and its function through cartoons and diagrams. On the other hand chemist need to look at the molecular level. The CPK ball and stick allows one to easily identify the bonding of the carbon, hydrogen and oxygen atoms. This representation will not show the folding of the proteins like that of the secondary structure. To understand how form matches function, the tertiary and the quaternary structures are useful for this purpose.
The three-dimensional structure of a protein is the feature that allows it to carry out its specific biological function. However, I must always remember that it is the primary structure, the order of the R groups, that determines how the protein will fold and what the ultimate shape will be.
