Question

Some hormone-receptor complexes are internalized by endocytosis. This process may involve A. binding of hormone-receptor complex to a clathrin coated pit. B. recycling of receptor to cell surface. C. degradation of receptor and hormone in lysosomes. D. formation of a receptosome. E. all of the above.

Short answer

A. Clathrin coated pit B. Recycling of receptor to cell surface C. Degradation in lysosomes D. Formation of a receptosome E. All of the above Answer: E. All of the above

Step-by-step solution

Option A: Clathrin coated pit

Clathrin coated pits are structures on the cell surface that mediate endocytosis, which is the process by which cells internalize extracellular substances. Hormone-receptor complexes can bind to clathrin coated pits, initiating the endocytosis process. Therefore, option A is relevant to the process.

Option B: Recycling of receptor to cell surface

After the hormone-receptor complex is internalized through endocytosis, the receptor can be recycled back to the cell surface to bind to more hormones. This process contributes to the regulation of hormone signaling in cells. Hence, option B is relevant to the process.

Option C: Degradation in lysosomes

After internalization, hormone-receptor complexes can be targeted for degradation. They are transported to lysosomes, where enzymes break them down into their constituent parts. This step helps control the availability of active hormone-receptor complexes in the cell. Therefore, option C is relevant to the process.

Option D: Formation of a receptosome

A receptosome is an endocytic vesicle that contains internalized hormone-receptor complexes. After endocytosis, the hormone-receptor complex is enclosed within a vesicle in the cell. This vesicle, known as a receptosome, transports the complex to its final destination (such as a lysosome or back to the cell surface). Hence, option D is relevant to the process.

Conclusion

Each of the given options is involved in the process of endocytosis of hormone-receptor complexes. Therefore, the correct answer is E. all of the above.