Question

increased expression and activity of the gated ca2+ protein channel trpv1 has been shown to block cell division and induce apoptosis in human cells. the structure of trpv1 ca2+ ion channel consists of several transmembrane domains that are embedded in the membrane as well as a carboxy - terminus and an amino - terminus that are located inside the cell (figure 1).
opening of trpv1 is activated by several stimuli, including the binding of capsaicin, a chemical found in chili peppers. capsaicin enters the cell by simple diffusion and then binds to one of the transmembrane domains of trpv1, which opens the ion channel. the opening of the trpv1 channel allows ca2+ ions to enter the cell (figure 2).
(a) based on the information provided, describe how a net movement of ca2+ ions into the cell occurs in cells with trpv1 proteins. (1 point)
(b) based on the information provided, predict the chemical and structural properties of the molecule capsaicin. (1 point)
(c) explain how the trpv1 ion channel is anchored in the plasma membrane by describing properties of the transmembrane domains of the protein. (1 point)
(d) predict one condition that would prevent the influx (net movement) of ca2+ ions into the cell. (1 point)

Explanation:

Step1: Answer (a)

When capsaicin binds to a transmembrane domain of TRPV1, the TRPV1 ion - channel opens. This allows Ca2+ ions to move down their concentration gradient into the cell, resulting in a net movement of Ca2+ ions into the cell.

Step2: Answer (b)

Since capsaicin enters the cell by simple diffusion, it is likely to be a small, non - polar molecule. Non - polar molecules can pass through the non - polar interior of the phospholipid bilayer easily.

Step3: Answer (c)

The transmembrane domains of the TRPV1 protein likely contain hydrophobic amino acids. These hydrophobic amino acids interact favorably with the non - polar fatty acid tails of the phospholipids in the plasma membrane, anchoring the TRPV1 ion channel in the membrane.

Step4: Answer (d)

One condition that could prevent the influx of Ca2+ ions is the absence of capsaicin or a lack of functional TRPV1 proteins. Without capsaicin binding to TRPV1, the ion channel will not open, and Ca2+ ions will not enter the cell. Another condition could be a mutation in the TRPV1 protein that prevents it from opening even in the presence of capsaicin.

Answer:

(a) Capsaicin binding to TRPV1 opens the channel, allowing Ca2+ ions to move down their concentration gradient into the cell.
(b) Capsaicin is likely a small, non - polar molecule to allow for simple diffusion across the cell membrane.
(c) The transmembrane domains of TRPV1 contain hydrophobic amino acids that interact with the non - polar fatty acid tails of phospholipids in the plasma membrane.
(d) Absence of capsaicin or non - functional TRPV1 proteins.