[Campbell Biology P.272] Which of the following statements accurately describes the characte... | Practice Question

Which of the following statements accurately describes the characteristics and examples of second messengers, as presented in the text?

  • A: They are large, insoluble proteins that cannot diffuse freely within the cell.
  • B: They are extracellular signaling molecules that bind to membrane receptors.
  • C: Cyclic AMP and calcium ions (Ca2+) are common examples, facilitating signal propagation within the cell.
  • D: Their primary function is to directly activate G protein-coupled receptors.

Explanation

The text explicitly states that second messengers are 'small, nonprotein, water-soluble molecules or ions' that 'can readily spread through regions of the cell by diffusion'. It also identifies 'cyclic AMP and calcium ions, Ca2+' as 'the two most common second messengers'.