Question

Hormones are chemical messengers that travel via the bloodstream and trigger cellular responses in a wide variety of target cells. The diagrams below illustrate the main difference in signaling pathways between steroid and protein hormones.
In both diagrams:
a = hormone
b = cell membrane
c = cytoplasm
d = nucleus
This indicates that the cell signaling pathway of steroid hormones differs from the pathway of protein hormones in the respect that steroids:

• A. Initiate a transduction pathway by binding to a receptor in the nucleus and activating transcription. Protein hormones bind to receptors in the cytoplasm in order to begin transduction, which results in transcription.
• B. Bind to a cell membrane receptor, which initiates transduction and ends with the activation of transcription factors in the nucleus. Protein hormones also bind to membrane receptors, but do not initiate transduction.
• C. Pass freely through the cell membrane and bind to a receptor on the nuclear membrane, which results in the transcription of a gene. Protein hormones bind to membrane receptors and initiate a transduction pathway, which results in a series of enzyme activations ending in a response in the nucleus.
• D. Pass freely through the cell membrane and travel into the nucleus which results in enzyme activation and transcription. Protein hormones bind to membrane receptors and initiate a transduction pathway, which results in a series of enzyme activations, ending in a response in the nucleus.

Answer 1

The correct option is D Pass freely through the cell membrane and travel into the nucleus which results in enzyme activation and transcription. Protein hormones bind to membrane receptors and initiate a transduction pathway, which results in a series of enzyme activations, ending in a response in the nucleus.

1. Steroid hormones are made up of cholesterol while peptide hormones are made up of amino acids.
2. Since the steroid hormones are made of lipids they can easily pass through the plasma membrane and bind to the receptors on the nucleus and effects the DNA transcription.
   
3. Protein hormones are made of amino acids they bind to the receptors of the plasma membrane of the receptor cell and activate secondary messenger system.

So, the correct answer is D.