<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
The diaphragm on a compound microscopes serves to control and regulate the amount of light reaching the specimen
I could be wrong but I would say D
The structures which are part of the upper respiratory system include the following:
<h3>What is Respiratory system?</h3>
This is the system which is involved in the gaseous exchange of organisms and consists of organs such as lungs etc.
The parts mentioned above are found in the upper respiratory tract of most animals.
Read more about Respiratory system here brainly.com/question/2619922
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