Cell membranes perform all the following functions except— a) making nutrients for cells b) holding cytoplasm within cells c) regulating substances exiting cells d) recognizing other cells

Cell membranes do not make nutrients (or energy) for the cells. This is the function of the mitochondria by the electron transport chain, tricarboxylic acid cycle, and beta oxidation. The cell membrane is responsible in holding the cytoplasmic components of the cells. The cell membrane is also involved in substance regulation by acting as a semi-permeable membrane for simple diffusion as well as the site where carrier proteins are embedded for facilitated diffusion (not ATP requiring) and active transport (ATP requiring). The cell membrane is also involved in cell to cell recognition because receptors are also embedded in the cell membrane. 

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