Question

Choose the correct answer from the alternatives given.
A major difference in the mechanism of action between steroid and peptide hormones is that:

• A. steroid hormones affect the synthesis of proteins, whereas peptide hormones affect the activity of proteins already in the cell
• B. target cells react more rapidly to steroid hormones than they do to peptide hormones
• C. steroid hormones bind to a receptor protein, whereas peptide hormones bind to G protein
• D. steroid proteins affect metabolism, whereas peptide hormones affect membrane permeability

Answer 1

The correct option is A steroid hormones affect the synthesis of proteins, whereas peptide hormones affect the activity of proteins already in the cell

Peptide hormones are hydrophilic due to which they are unable to cross the lipid plasma membrane. They bind to the receptors on the plasma membrane and affect the activity of proteins inside the cell called secondary messenger. These secondary messengers then perform the action required. The steroid hormones are hydrophobic, they can cross the plasma membrane directly and are able to affect the synthesis of proteins directly in the cells.

Hence, the correct answer is 'steroid hormones affect the synthesis of proteins, whereas peptide hormones affect the activity of proteins already in the cell'.