Scientists are studying the structure and function of receptor x, a single-polypeptide protein that is found in the membrane around certain types of cells. receptor x contains no alpha- helices or beta sheets. a specific molecule outside the cells is recognized and bound by receptor x. the binding of the molecule to receptor x causes the cells to have a particular response. to study the structure and function of receptor x the scientists are altering the sequence of small sections of the receptor. both the normal sequence of a five-amino acid section of receptor x and an altered sequence that contains two amino acid substitutions are shown in figure 1.

Choose the incorrect statement (a) the motor end plate membrane is only capable of generating graded potentials, but it is contiguous with the skeletal muscle sarcolemma, which can generate action potentials. (b) propagation of an action potential through the t-tubules into the sarcoplasmic reticulum triggers the release of ca++ into the cytoplasm of a skeletal muscle fiber. (c) the generation of suprathreshold endplate potentials in multiple muscle fibers could be due to the increased frequency of action potential generation at the axon hillock of a single motor neuron. (d) a greater amount of ach would be found in the presynaptic vesicles of a motor unit that fired several action potentials after exposure to botulinum toxin, than in a motor unit that fired several action potentials after exposure to the venom of the krait snake (which contains α-bungarotoxin).