Virtually all amino acid-based hormones exert their signaling effects through intracellular

a) store iron in the liver: Ferritin is an intracellular protein that stores iron and releases it in a controlled fashion. It is primarily found in the liver, spleen, and bone marrow.

b) Absorb iron across intestinal cells: DMT1 (divalent metal transporter 1) and ferroportin are more directly involved in this.

c) Oxidize iron in the peroxisomes: Iron oxidation is not a function of peroxisomes, nor of ferritin.

d) Transport iron in the blood: Transferrin, not ferritin, is responsible for iron transport in plasma.

a) They cross the plasma membrane.
Amino acid-based hormones are water-soluble and cannot easily cross the lipid bilayer of the plasma membrane.

b) They are lipid soluble.
Unlike steroid hormones, amino acid-based hormones are not lipid-soluble; they are hydrophilic.

c) They are synthesized from cholesterol.
Steroid hormones are synthesized from cholesterol, not amino acid-based hormones.

d) They require a receptor in the plasma membrane.
Due to their inability to cross the plasma membrane, amino acid-based hormones bind to cell surface receptors to trigger intracellular responses via second messengers.