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9. Membrane proteins are proteins that are suspended within the lipid bilayer of a membrane. They are held in place because some R-groups of the protein interact with the phosphate heads of the phospholipids of the membrane, while other R-groups of the protein interact with the hydrocarbon tails of the phospholipids of the membrane. From the amino acids shown below, which one likely has an R-group that interacts with the phospholipid tails? (Note: the R-groups are highlighted in color)