Final answer:
Peptide or protein hormones are both hydrophilic and lipophobic because they are composed of chains of amino acids, making them water-soluble but not lipid-soluble. They require cell surface receptors to transmit their signals.
Step-by-step explanation:
Peptide or protein hormones are classified as both hydrophilic and lipophobic due to their structure and solubility properties. These hormones are composed of chains of amino acids and are water-soluble, meaning they readily dissolve in water.
Their hydrophilic nature allows them to easily travel through the bloodstream to reach their target cells or tissues. However, these hormones are lipophobic, meaning they do not readily dissolve in lipids or fats.
Due to this characteristic, they require cell surface receptors to transmit their signals, as they cannot cross the cell membrane like lipid-soluble hormones.