Protein Functions

by Kevin Ahern, PhD

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    In this lecture, I will discuss four more functions proteins carry out for the organisms and the cells within them. These functions include proteins functioning as antibodies in the immune system, proteins and their role in regulating gene expression, proteins acting as enzymes to catalyze reactions, and finally proteins acting to transport materials across biological membranes and within organisms. Now multicellular organisms have an immune system that protects them against outsiding invaders. The functional parts of the immune system are antibodies, as seen in this slide. Antibodies are proteins that are produced by the adaptive immune system of a multicellular organism. Now the antibodies are the functional part of that adaptive immune system. They recognize and bind to specific molecules, and those specific molecules are called antigens as seen on the screen above. The remarkable thing about the adaptive immune system is that antibodies can be created to recognize things that the body never before encountered. Now antibodies are present in both soluble forms, meaning released freely, and also in membrane-bound forms. The structure of antibodies is shown on the screen, and in this slide you can see that the antibody consists of four polypeptide chains. Two long chains that are called heavy chains that are the central part of the Y, and the two heavy chains are joined to each other at the bottom of the Y by disulfide bonds. The antibody also consists of two light chains that are joined to the heavy chains at the upper part of the Y. The light chains are joined to the heavy chains also by disulfide bonds. Now as we examine the antibody overall, we see that there are different regions of the antibody that have functions that they perform in the recognition. For example, the bottom part of the antibody...

    About the Lecture

    The lecture Protein Functions by Kevin Ahern, PhD is from the course Biochemistry: Basics. It contains the following chapters:

    • Antibodies
    • Gene Expression
    • Catalysis
    • Transport Proteins
    • Oxgen Transport
    • Sodium-Potassium ATPase

    Included Quiz Questions

    1. ...antibodies bind and recognize “foreign” molecules.
    2. ...antigens have a “Y” shaped structure.
    3. ...the constant region of the antibody is the binding portion of the molecule.
    4. ...the immune response is generated by injection of antibodies into the bloodstream.
    1. ...methylation of DNA plays a role in determining if the process occurs.
    2. ...RNA polymerase binds the promoter in DNA without assistance.
    3. ...transcription factors work by binding to RNA.
    4. ...the promoter is a sequence in RNA.
    1. Turnover number describes how fast enzymes are made and destroyed.
    2. The Koshland mechanism describes how enzyme flexibility enables catalysis.
    3. Binding of substrate induces structural changes in enzymes leading to catalysis.
    4. Reaction products induce additional structural changes in the ES complex.
    1. ...they include complexes like LDLs and HDLs.
    2. ...they do not move ions.
    3. ...in the bloodstream, they carry polar compounds within a non-polar outer shell.
    4. ...they only work outside of cells.
    1. ...requires ATP.
    2. ...is a synport.
    3. ...uses energy from the sodium gradient to move potassium.
    4. ...is embedded in the mitochondrial membrane.
    1. ...exhibits cooperativity in binding to oxygen, but myoglobin does not.
    2. ...requires ATP to carry oxygen.
    3. ...saturates with oxygen at low oxygen concentrations.
    4. ...has a greater affinity for oxygen than myoglobin.

    Author of lecture Protein Functions

     Kevin Ahern, PhD

    Kevin Ahern, PhD

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