which is true about targeting of the secretory proteins? group of answer choices a) signal recognition particle (srp) binding to the signal peptide and ribosome temporarily accelerates protein synthesis. b) the newly synthesized polypeptides include a signal peptide at their carboxyl termini. c) the signal peptide is cleaved off inside the mitochondria by signal peptidase. d) the signal recognition particle (srp) binds to the signal peptide soon after it appears outside the ribosome. e) the signal sequence is added to the polypeptide in a posttranslational modification reaction.