Explanation:
Receptors are specific molecular components of a biological system with which drugs interact to produce changes in body function. This fundamental event of drug-receptor interaction initiates communication, through signal molecules (first messenger) of great structural and functional diversity, with receptors coupled to ionic channels, to G-proteins, catalytic or regulators of DNA transcription, as well as The integrated support of second messengers. It also mentions certain diseases that arise due to dysfunction of these receptors of the receptor-effector systems, such as the appearance of aberrant receptors or as products of "oncogenes".
water travels up the xylem due to transpiration
1. A phosphate group. These give the molecule a negative charge.
2. A nitrogen base. There are four different nitrogen bases though, so be careful. The four different nitrogen bases are Adenine, Guanine, Cytosine, and Thymine.
Endoskeleton
A. Insects and crustaceans
B. Fish
C. Insects especially the pollinators
D. All vertebrates <span />
fossil b belongs to the same period as trilobite because its on the same layer as the rhombus with a diagonal, which is fossil B