added in lipidation, these proteins go into the membranes found in vesicles, mitochondria, endoplasmic reticulum, Golgi apparatus, and the plasma membrane. Proteolysis tends to be irreversible. Proteases are enzymes that cleave peptide bonds in post-translational protein modification. There are regulatory processes that make sure that proteolysis doesn’t become uncontrolled.
ENZYMOLOGY Enzymes are all catalysts for chemical reaction but not all catalysts are enzymes. The catalyst in any reaction will lower the activation energy of a reaction, allowing the reaction to proceed faster. In biological systems, the enzymes are almost always proteins; however, some ribosomal RNA molecules can be enzymes as well. As we have discussed in a previous chapter, enzymes will bind to reactants or substrates in a reaction, holding them in a way such that the chemical process can become the endproduct much more efficiently. Figure 33 shows what enzymes do in order to facilitate a reaction:
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