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Chemistry LibreTexts

Case Studies: Proteins

  • Page ID
    493
    • Angiotnesin Peptide
    • Enkephalines
    • Membrane Transport
      Membrane transport is essential for cellular life. As cells proceed through their life cycle, a vast amount of exchange is necessary to maintain function.  Transport may involve the incorporation of biological molecules and the discharge of waste products that are necessary for normal function. 1 Membrane transport refers to the movement of particles (solute) across or through a membranous barrier. 2 These membranous barriers, in the case of the cell for example, consist of a phospholipid bilayer. The phospholipids orient themselves in such a way so that the hydrophilic (polar) heads are nearest the extracellular and intracellular mediums, and the hydrophobic (non-polar) tails align between the two hydrophilic head groups. Membrane transport is dependent upon the permeability of the membrane, transmembrane solute concentration, and the size and charge of the solute. 2 Solute particles can traverse the membrane via three mechanisms: passive, facilitated, and active transport. 1 Some of these transport mechanisms require the input of energy and use of a transmembrane protein, whereas other mechanisms do not incorporate secondary molecules. 3
    • Permanent Hair Wave
      The formation of disulfide bonds has a direct application in producing curls in hair by the permanent wave process. Hair keratin consists of many protein alpha-helices. Three alpha-helices are interwoven into a left-handed coil called a protofibril. Eleven protofibrils are bonded and coiled together to make a microfibril. Hundreds of these microfibrils are cemented into an irregular bundle called a macrofibril. These in turn are mixed with dead and living cells to make a complete strand of hair.
    • Sickle Cell Anemia
      The incorrect amino acid sequence in a protein may lead to fatal consequences. For example, the inherited disease, sickle cell anemia, results from a single incorrect amino acid at the 6th position of the beta - protein chain out of 146. Hemoglobin consists of four protein chains - two beta and two alpha.