Which of the following molecules is a pyrimidine?
a. guanine
b. phosphate
c. uracil
d. adenine
Answer: c. uracil
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Some drugs are now being delivered into cells through liposomes, where the drug is surrounded by a phospholipid bilayer. How do the drugs enter into the cell?
A. The drug destroys the liposome and is transported via diffusion into the cell. B. The liposome cuts a hole in the cell and injects the drug into the cell. C. The liposome fuses with the phospholipid bilayer of the cell. D. Protein channels on the cell surface transport the liposomes into the cell.
Potassium deficiency in plants occurs when plants grow on light, sandy soils and cannot obtain enough potassium ions. Such plants are deficient in: (check all that apply)
_____ an essential element. _____ a macronutrient. _____ a micronutrient. _____ a limiting factor.
Four of the five features listed below are
characteristic of bilaterally symmetrical organisms. Select the exception. a. sessile, nonmoving b. three germ layers c. cephalization d. paired nerves, muscles, sensory structures e. right and left halves of the body
The ________ definition of species says that a species is a group of organisms that are reproductively isolated from other such groups.
Fill in the blank(s) with the appropriate word(s).