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Unformatted text preview: Chapter 3 The Macromolecules of the Cell Proteins- 9 major types o Enzymes – catalyzes reactions o Structural proteins – support for cellular structure Collagen, elastin for animal connective tissue; keratin for hair o Motility proteins – movement of cells and cell parts Actin, myosin for muscles; tubulin for cilia and flagella o Regulatory proteins – regulation of cell functions Transcription factors regulate read-out of genetic information o Transport proteins – transport of substances into, out of, within cells Some are embedded within the membrane to mediate glucose transport o Hormonal proteins – communication between distant parts of organism Insulin from pancreas on concentration of glucose o Receptor proteins – response of cells to stimuli Nerve cell detects chemical signals from other nerve cell o Defensive proteins – protection against disease Antibodies detect and destroy bacteria and viruses o Storage proteins – stores and releases amino acids- Amino acid monomers o 20 different kinds used in protein synthesis o Two stereoisomeric forms L-amino (the only one that exist in proteins) and D-amino o Carbon bound to four groups: hydrogen, R group, amino group, carboxyl group o Grouped in three categories Non-polar/Hydrophobic – contains hydrocarbon R groups (9) Polar, uncharged/hydrophilic – slight polarity but no ions (6) Polar, charged/hydrophilic – ionic in nature (5) o Stringed up into polymers Dehydration reaction – flushes water out to form covalent bond/peptide bond between amino acids • Connection at the C-terminus on amino acid 1 and N-terminus on amino acid 2 Ribosomes involved in elongating amino acid chain • Polypeptide is formed- Polypeptide chain that has attained unique, stable, 3D shape and is biologically active o Monomeric proteins – contain a single polypeptide o Multimeric proteins – consist of two or more polypeptides Hemoglobin – 2 alpha globin subunits, 2 beta globin subunits- Protein folding o Several types of bonds involved in conformation Disulfide bonds – bonded sulfhydryl groups are extremely rare, though strong • Maintains protein structure, but not the most important Hydrogen bonds – forms between hydrogen and oxygen, very common and abundant, but very weak • Important for stabilizing helical and sheet structures Ionic bonds – some positively and negatively charged R groups bind together • Can be disrupted by drastic increase or decrease of pH Van der Waals interactions – slight attraction of nonpolar molecules at a certain distance • Unstable and weak, but important nonetheless Hydrophobic interactions – molecules exclude themselves from interactions with water • Tend to locate themselves inside polypeptide, huddled near each other o Four stages of folding Primary structure – amino acid sequence of polypeptide(s) Secondary structure – patterns of local structure, with 2 major structural patterns...
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