Indicate whether the following statements are true:
(a) Proteins with the sequence Lys-Phe-Glu-Arg-Gln are selectively degraded by proteasomes.
(b) Proteins containing sequences rich in Pro, Glu, Ser, and Thr often have short halflives.
(c) The addition of ubiquitin protects segments of a protein from proteolysis.
(d) Lysosomal proteases degrade only extracellular proteins that enter the cell by endocytosis.
(e) The ubiquitin-transfer reactions catalyzed by E2 and E3 do not require the input of free energy in the form of ATP?