When the nerve impulse reaches the end of the axon, it stimulates the release of a chemical that stimulates depolarization of the next neuron in the chain. This chemical is
A. acetylcholine.
B. acetylcholinesterase.
C. thyroxine.
D. estrogen.
A. acetylcholine.
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A number of systems for pumping ions across membranes are powered by ATP. Such ATP-powered pumps are often called ATPases, although they do not often hydrolyze ATP unless they are simultaneously transporting ions
Because small increases in calcium ions in the cytosol can trigger a number of different intracellular reactions, cells keep the cytosolic calcium concentration quite low under normal conditions, using ATP-powered calcium pumps. For example, muscle cells transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (SR). If a resting muscle cell's cytosol has a free calcium ion concentration of 10-7 while the concentration in the SR is 10-2, then how is the ATPase acting? A) ATPase activity must be powering an inflow of calcium from the outside of the cell into the SR. B) ATPase activity must be transferring i to the SR to enable this to occur. C) ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient. D) ATPase activity must be opening a channel for the calcium ions to diffuse back into the SR along the concentration gradient. E) ATPase activity must be routing calcium ions from the SR to the cytosol, and then to the cell's environment.
In the context of the influenza virus, describe the mechanistic difference between an antigenic drift and an antigenic shift. Also indicate the result of each
What will be an ideal response?
He believed that disease had natural causes, e.g., "The Four Humor Theory". and that it could be cured by rational methods.
A. Imhotep B. Asclepius C. Hippocrates D. Fracastoro
A reaction in which the forward rate is equal to the reverse rate is said to be at ________.
Fill in the blank(s) with the appropriate word(s).