Which of the following substances would have the most trouble crossing a biological membrane by diffusing through the lipid bilayer?
A) O2
B) CO2
C) Na+
D) a small, nonpolar molecule such as butane (C4H10)
Answer: C
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The prevalence of the allele for sickle cell anemia in some populations is an example of?
A. Heterogeneous environments B. Balancing selection C. Inverted selection D. Non-Darwinian selection E. Nonrandom mating
Which of the following best explains why bees aren't attracted to red flowers?
A. Bees perceive red as a warning signal. B. Bees can't see red. C. Red flowers usually are odorless. D. Red flowers do not produce nectar. E. Red flowers are imperfect and do not produce pollen.
Which of the following could likely play a role in causing cancer?
1.Cells adhere too strongly to one another, causing a tumor to form. 2.Kinase enzymes add phosphates onto proteins that regulate the cell cycle. 3.The cell cycle skips interphase. 4.Checkpoint proteins make cells “commit suicide.”
)
A. The suspected pathogen infects animals but not humans. B. The suspected pathogen cannot be cultured in the laboratory. C. There is not a suitable experimental host for the suspected pathogen. D. The suspected pathogen produces disease both in humans and a suitable test animal. E. The disease is polymicrobial, caused by more than one pathogen.