Ultimately, the signal from a peptide hormone is typically conveyed to the effectors in the cell via the transfer of what molecular moiety?

Question

A.  nucleotide
B.  NO (nitric oxide)
C.  H2O
D.  phosphate group
E.  amino acid

Clarify Question
What is the key concept addressed by the question?
What type of thinking is required?

Gather Content
What do you already know about peptide receptors? What other information is related to the question?

Choose Answer
Given what you now know, what information is most likely to produce the correct answer?

Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

D.  phosphate group

Clarify Question
What is the key concept addressed by the question?
        · What intracellular molecule transmits peptide hormone signals?
What type of thinking is required?
            o This is an analyze question because you have to discriminate between different potential signaling molecules.

Gather Content
What do you already know about peptide receptors? What other information is related to the question?
        · Peptide hormone receptors can either be a G protein-coupled receptor or a receptor kinase. G protein-coupled receptors are found in the cell membrane and ligands outside of the cell bind to the receptors to activate G proteins located inside the cell. When activated, G proteins bind to GTP and are released from the receptor. These G proteins in turn activate second-messenger producing enzymes to elicit changes within the cell. Such receptors are important for hydrophilic molecules such as protein hormones which cannot cross the phospholipid bilayer of the cell membrane. Receptor kinases, like receptor tyrosine kinases, autophosphorylate and then phosphorylate other proteins which induce cellular pathways. In both types of receptors, the intracellular cascade often involves one or a series of kinases each transferring a phosphate group onto their targets.

Choose Answer
Given what you now know, what information is most likely to produce the correct answer?
       · Nucleotides are found in DNA and RNA. Since peptide hormones do not enter the nucleus like steroid hormones do, they would not regulate gene expression to produce an effect. Water is anubiquitous molecule both intracellularly and extracellularly (most of the cell is composed of water). Thus, it would not make a good signaling molecule. Nitric oxide is known to act as a hormone and neurotransmitter, but it is a gas, not a peptide hormone. Amino acids are what proteins are made of, but peptide hormones do not disintegrate into amino acids to elicit their effects- the amino acids are needed to maintain the three-dimensional structure of the protein so it will fit its appropriate receptors. That leaves phosphate groups. In both types of peptide hormone receptors, G protein-coupled receptors and receptor kinases, phosphorylation, or the addition of phosphate groups to activate proteins, is involved.

Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
       · Answering this question correctly depended upon analyzing each potential molecular moiety for sensibility to be the most important signaling molecule for hydrophilic (peptide) hormones. If you got the answers correct, great! If not, which answer did you choose? Did you think that because peptide hormones are made of amino acids, that amino acid would be the answer? That is true, but amino acids do not break off of peptides to become signaling molecules. Since hormone regulation often leads to shifts in gene expression, did you think that nucleotide was the answer? Hormones that directly regulate DNA are hydrophobic (steroid) ones, not peptides.