In the autoimmune disease multiple sclerosis, a person’s immune system attacks and destroys
the myelin sheath cells. What occurs as a result of the destruction of these cells?
a. The speed of action potentials decreases.
b. The sodium–potassium pumps malfunction.
c. Signals cannot be transmitted across the synapse.
d. Action potentials can travel in two directions
A
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What is one reason that RNA viruses and retroviruses have such a high rate of mutation?
A. because RNA replication is much more prone to mistakes B. because RNA viruses and retroviruses initially cause mutations during replication C. because RNA is more fragile than DNA and therefore more likely to be damaged D. because they lack a proofreading mechanism E. because RNA is more fragile than DNA and because viral polymerases lack a proofreading mechanism.
Which functional group acts as an organic base?
a. carbonyl b. hydroxyl c. phosphate d. amino
e. carboxylWhat type of transporters will allow ions to cross the membrane through open or gated channels?
a. Active b. Recognition c. Adhesion d. Passive e. Receptor
The seed coat develops from the
A) integuments of the ovule. B) wall of the pollen sac. C) ovary wall. D) female gametophyte. E) endosperm.