Answer
c.
Work Step by Step
The question asks which option is not correct about peptide hormones, so we want to find which option is false.
Option a. is incorrect. Peptide hormones are secreted into the bloodstream by endocrine glands such as epinephrine secreted by the adrenal glands. This option is, therefore, true and not the correct answer.
Option b. is incorrect. Peptide hormones don't enter cells; instead, they bind to a receptor on the plasma protein. This option is, therefore, true and not the correct answer.
Option c. is correct. Peptide hormones do not enter cells; they bind to a receptor on the membrane, thus causing a secondary messenger such as cyclic AMP (cAMP) to be produced inside the cell. This option is, therefore, false and is the correct answer.
Option d. is incorrect. Peptide hormones binding to a receptor on the plasma membrane causes the production of a secondary messenger within the cell. This option is, therefore, true and not the correct answer.
Option e. is incorrect because not all of the options are correct.
