341lecture06sept21sakai

341lecture06sept21sakai - Cell Biology 341 Last lecture:...

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Cell Biology 341 Monday, Sept. 21, 2009 Today: last section of chapter 3 on regulation of enzymes Begin chapter 4 on DNA and chromosome structure Go to Molviz.org and view the Hemoglobin and Antibody (parts 1-4) tutorials Last lecture: Extracellular proteins contain disulfide bonds (covalent) Antibodies contain 2 heavy chains and 2 light chains Part of the energy released in breakdown reactions is stored in carrier molecules such as ATP and NADH Enzymes may only catalyze energetically favorable reactions or pathways Coupled enzymatic reactions must have a net negative ΔG Enzymes lower the activation energy of a reaction Pathways may be regulated by feedback inhibition
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Back to Chapter 3: Protein Function pages 152-179
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Enzymes bind their substrate(s) in the active site Enzymes are highly specific for their substrates, for example, binding only one optical isomer with high affinity Multiple noncovalent bonding forces are usually involved in binding the substrate molecule The rate of the reaction depends on the [substrate]- see figure 3-45 the cyclic AMP binding site on the CAP protein (in this case, CAP is not an enzyme, so we call cAMP a ligand ) Proteins such as hemoglobin or receptors also bind their ligands in highly specific binding sites Figure 3-37
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341lecture06sept21sakai - Cell Biology 341 Last lecture:...

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