Major Themes in Biochemistry

Reflecting back on the course, what are three major themes you would identify that connect the various topics discussed in this course – how are they connected to more than one topic, and how do they connect with what you knew before this course?  What knowledge have you gained with regards to these three themes you have identified?

Three major themes in this course that I would identify as themes that connect the various topics discussed in this course would be:

Molecules as Building Blocks, Activity vs Inactivity, and Major Macromolecules as Energy Sources

 Molecules as Building Blocks: This theme was made evident in Biochem through the various lecture topics which all addressed at least one of the four classes of small molecules (amino acids, carbs, lipids, and nucleosides or nucleotides) as the building block to one or more important biomolecular structures. 


Activity vs Inactivity: This theme was made evident in Biochemistry lecture topics which explored stereoisomers of different biomolecular structures and their optically active forms vs their inactive forms. Stereoisomers are compounds with the same kinds and numbers of atoms, but with different molecular arrangements. Typically, most of the biomolecular structures that we discussed are only found in one of the possible stereoisomers. The naming systems which we learned (L/D forms and Alpha/Beta forms) help to distinguish whether or not a compound is in its active form or not and also whether or not there needs to be any conformational changes made to the structure before it can play its role in whatever process it may be involved in.


Macromolecules as Energy Sources: This theme was prominent throughout all of our lectures in Biochem and can possibly even be seen as an umbrella theme under which many of the others fall. The different cycles and mechanisms which we explored as part of the cycle of cellular respiration all play a role in the breakdown of Carbs, Protein, and Fat so that those macromolecules can be utilized for energy sources. What I found especially interesting about this theme in biochemistry was discovering how many ways these macromolecules can be used and the functions they serve in the body. For example, proteins are not just the building blocks of muscle tissue but can be found as part of DNA structure, hormones, enzymes, and as the material for many other essential structures and substances. Carbohydrates make up different parts of nucleotides and are also present in some components of ALL cell membranes. Lipids too are an essential component of membranes, and they also help to transport some vitamins (lipid soluble ones A,D,E,K) and are important energy stores in both plans and animals. 

Glucose and Energy

How would you explain the connection between glucose entering the body and energy created by the body to a friend, using your new biochemistry knowledge? The foods that we eat are mixed with acid and enzymes on the way from our mouth into the stomach and finally the intestines, where the majority of the breakdown takes place. By 'breakdown', what I am referencing is the process by which the energy you ingest in the form of whatever food it is that you eat is subjected to these acids and enzymes which break the food up into molecules of sugars, called glucose. This glucose is absorbed by the stomach and small intestines and then released into the bloodstream, where it can be utilized as an immediate source of energy, or it can be stored back in our bodies to be used at a later time. The hormone insulin plays a key role in regulating the amount of glucose in the bloodstream at any given time. Insulin that is released from the pancreas travels through the bloodstream to the body's cell and orders that the glucose be let inside. Inside the cell, the cellular respiration set of metabolic reactions takes place and the glucose can either be utilized or stored. For example, if a large meal is eaten, and the body doesn't need that much glucose right away, insulin will act to help the body store the glucose so that it can be converted into energy later. The method by which insulin helps to store glucose involves larger packages of glucose, called glycogen. These glycogen packages are stored in both the liver and the muscles. One more important note about insulin is that in addition to helping us store the glucose from the meal, it can also help store the fat and the protein too. As discussed in class, although glucose is the preferred energy source, the body will also resort to fat stores and even protein if it is in a state where it requires the extra energy.

L-Carnitine

Thus far in Biochemistry, some new knowledge that I have connected with past knowledge is about the ammonium compound carnitine, which is biosynthesized from the amino acids lysine and methionine. Before learning about Carnitine in biochemistry, my only knowledge about it was from having seen it marketed as a workout supplement by itself, most often labeled as L-Carnitine.

In living cells, Carnitine is required for the transport of fatty acids from the cytosol into the mitochondria during the breakdown of lipids for the generation of metabolic energy. The reason that I have most often seen it labeled as L-Carnitine is because, as we learned in class, many amino acids (and other products of metabolism) have two forms that are mirror images of each other and are considered the L and D forms of the substance, based on chemical structure. the L form is the biologically active form of Carnitine, whereas the D-form is the enantiomer and is not a marketed product because it is biologically inactive.

Even if you are not considered an athlete, there is medical evidence that suggests that the body's production of carnitine slows just with age. As a result, many nutritionists have begun suggesting that their older clients increase dietary sources of carnitine, which are mainly derived from the muscle, kidney, and liver content of animal products but some plant sources can also be found in avocado, alfafa, and wheat germ.