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Introduction to Biomolecules in BIS2A

  • Page ID
    21297
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    Introduction to Biomolecules in BIS2A

    Some context and motivation

    In BIS2A we want to learn how living systems "work". To accomplish this we need to understand the "stuff" biological systems. We want to know what "stuff" organisms are made of and how the properties of this "stuff" contribute to organismal forms and behaviors. This requires us to dig into a little chemistry — the science of the "stuff" that makes up the world we know. By doing so, we can show that many of the biological processes we care about arise directly from the chemical properties of the "stuff" that makes up living systems. Developing a functional understanding of some basic chemical concepts can, therefore, be tremendously useful in thinking about how to solve problems in medicine, energy, and environment by attacking them at their molecular levels. For these reasons, we begin a study of biomolecules and their chemistry. 

    Importance of chemical composition

    In this course, we want you to learn how to classify major classes of biological macromolecules into groups by looking at their chemical composition and, based on this composition, to also infer some properties they might have. For example, you will learn to recognize the molecular structures of carbohydrates. You'll learn to do so by spotting chemical "parts" on carbohydrates called hydroxyl groups and appreciate that those chemical "parts" can form special types of interactions called "hydrogen bonds". You'll discover how hydrogen bonds give carbohydrates special properties that govern how they interact with water and other molecules and how these interactions give different properties to carbohydrates like simple sugars and starches. This will shed light on the functional roles these molecules play in living systems, how they are built, and how they can be broken down. We will also look at other types of common macromolecules in biology in the same way. 

    Linking molecular structure to function

    In biology, structure is often said to "encode" function. That is, the shape and physical properties of something governs what it can do. In this course we want to make this general idea a bit more specific for you and begin to help you form the conceptual ideas that will help you explain how the chemical structure and properties of biomolecules can contribute to their functions.

    For example, biological membranes have the biological function of defining the boundaries between the inside and outside of a cell or compartments within a cell. The membranes also serve as selective barriers that allow certain things to pass into and out of a cell while excluding others substances from crossing the barrier. These are very important functions indeed! The chemical structures of membranes determine these functional properties. You will learn, for instance, that most membranes are composed of two layers of molecules called phospholipids  and that phospholipids can be schematically broken down into two chemically distinct subregions, a so-called hydrophilic head group and a hydrophobic tail group. Each of these chemical subregions and the chemical "parts" they are made of, contribute directly to determining the structure and permeability of cell membranes.

    Likewise, we will also learn about important biological molecules called enzymes. Enzymes help catalyze many of the chemical reactions in an organism, including how they process the food they eat, how an organism senses and interacts with its environment, and how it replicates (among many other functions). We will learn that the three dimensional structures of enzymes encode their functions and that their structures are determined to a large degree by the number, type, and order of chemicals called amino acids. The properties of these amino acids (and thus how they behave in an enzyme) are directly related to their own chemical "parts".  

    In sum, while structure "encodes" biological function, structure is itself usually determined by chemistry. Knowing a little bit of chemistry can be powerful in biology.

    Objectives and strategy

    On these notes we set out to learn a little bit of useful chemistry for biology. Our objectives for the next few weeks are fairly straightforward. First, we want to learn some basic vocabulary, symbols and models that help us communicate about chemistry in biology. Second, we want to learn a few basic ideas about what the "stuff-of-life" is made of and some basic properties of that stuff that help us understand biological phenomena. Third, we want to learn to recognize some of the most common chemical structures in biology and something about their properties. Fourth, we want to understand how some of the chemistries of the "stuff-of-life" can be altered and how this might change the function of a biomolecule. Fifth, we want to develop a vocabulary and learn key ideas that help us talk about how things change at the molecular level in biology. 

    If you've already taken some chemistry, some of the ideas will be familiar to you. If you haven't taken chemistry - or it's been a long time since you did - don't worry. We won't cover these topics in nearly as theoretically or in as much detail as your chemistry instructor will. We want to extract the most important ideas/concepts that help us function as general biologists. The core ideas and concepts aren't too complicated. However, there will likely be a lot of new vocabulary to learn and a good amount of practice required to get comfortable with thinking about things at the molecular scale. Success comes from practice. So, practice early and often. Strive to learn the new vocabulary quickly and take advantage of practice opportunities to think about molecules. That'll make it much easier to then think about and add new concepts as we go into the next few weeks. 


    This page titled Introduction to Biomolecules in BIS2A is shared under a not declared license and was authored, remixed, and/or curated by Marc Facciotti.

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