Which of the following statements is true of amino acid-based hormones?
They are synthesized from cholesterol.
They cross the plasma membrane.
They require a receptor in the plasma membrane.
They are lipid soluble.
The correct answer and explanation is:
The correct answer is: They require a receptor in the plasma membrane.
Amino acid-based hormones are a class of hormones that are primarily composed of amino acids or peptides. These hormones are water-soluble and do not easily cross the plasma membrane of target cells. This is in contrast to lipid-soluble hormones, such as steroid hormones, which can easily pass through the membrane due to their fat-soluble nature.
Because amino acid-based hormones cannot cross the cell membrane, they require receptors located on the cell’s surface. These receptors are typically embedded in the plasma membrane. When an amino acid-based hormone binds to its receptor, it triggers a series of intracellular signaling events. This mechanism is known as signal transduction. The binding of the hormone to its receptor activates various pathways inside the cell, leading to a physiological response. Common pathways include the activation of second messengers, such as cyclic AMP (cAMP), which relay signals inside the cell and activate specific enzymes or transcription factors.
Amino acid-based hormones are synthesized from amino acids rather than cholesterol. This is another key difference from steroid hormones, which are derived from cholesterol. Therefore, statements about amino acid-based hormones being synthesized from cholesterol or being lipid-soluble are incorrect.
In summary, amino acid-based hormones require a receptor in the plasma membrane because they are water-soluble and cannot penetrate the cell membrane. The receptor binding initiates a cascade of biochemical reactions that influence the cell’s function.