Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because 21)

a. many metabolic enzymes use dna as a cofactor, and affected individuals have mutations that prevent their enzymes from interacting efficiently with dna.

b. metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies.

c. enzymes are made of dna, and affected individuals lack dna polymerase.

d. genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.

e. certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors.

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).