Question

Testosterone movement across the cellular membrane

Testosterone is a small steroid hormone that is important in cell signaling. Which of the following indicates where testosterone enters a cell and why it is able to cross at that point?

a) Testosterone enters via active transport in the cytosol.
b) Testosterone diffuses through the nuclear membrane due to its size.
c) Testosterone enters through the plasma membrane by simple diffusion.
d) Testosterone is actively pumped into the mitochondria.

Answer 1

Testosterone, a steroid hormone, enters a cell through the plasma membrane by simple diffusion, due to its lipid-soluble nature, and binds to intracellular receptors to influence gene expression.

Step-by-step explanation:

The movement of testosterone across the cellular membrane occurs because testosterone is a lipid-soluble hormone. Steroid hormones like testosterone are capable of diffusing directly through the plasma membrane lipid bilayer without the need for active transport mechanisms. This process is known as simple diffusion. Once inside the cell, testosterone can bind to intracellular receptors either in the cytoplasm or in the nucleus, and the hormone-receptor complex then moves to the nucleus to influence gene expression by acting as a transcription regulator. Therefore, the correct answer to where testosterone enters a cell and why it is able to cross at that point is:

• Testosterone enters through the plasma membrane by simple diffusion.