<h2>a) is the correct option </h2>
Explanation:
The extracellular domain of the transmembrane receptor protein acts as binding site for primary messenger molecule whereas the transmembrane domain holds the receptor within membrane and the cytosolic domain has intrinsic tyrosine kinase activity, all these helps in proper cell signaling
If because of any mutation there is change in shape of the extracellular domain then that molecule that normally binds to the receptor protein will no longer attach hence cellular response will be deactivated
This means having no charge
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The mouth is the beginning of the digestive tract. In fact,digestion starts here as soon as you take the first bite of a meal. Chewing breaks the food into pieces that are more easily digested, while saliva mixes with food to begin the process of breaking it down into a form your body can absorb and use.
Hope This Helped! :3</span>