Which of the following statements about hormones is correct? a. steroid and peptide hormones produce different effects but use the same biochemical mechanisms. b. steroid and peptide hormones produce the same effects but differ in the mechanisms that produce the effects. c. steroid hormones affect the synthesis of proteins, whereas peptide hormones affect the activity of proteins already present in the cell. d. steroid hormones affect the activity of certain proteins within the cell, whereas peptide hormones directly affect the processing of mrna. e. steroid hormones affect the synthesis of proteins to be exported from the cell, whereas peptide hormones affect the synthesis of proteins that remain in the cell.