Langur monkeys and ruminants (such as cows) are the only known mammals in which lysozyme functions in the stomach instead of in tears and saliva. The cow/langur enzyme also has five amino acid changes that are not present in other mammals. What is most likely to be true about lysozyme from langurs and cows compared to lysozyme from other mammals?
A. These five amino acid changes alter the specificity of the enzyme, such that the cow/langur lysozyme attacks viruses instead of bacteria.
B. These five amino acid changes somehow make the cow/langur lysozyme resistant to pepsin digestion.
C. Salivary and tear lysozyme functions best at a higher H+ ion concentration than the cow/langur enzyme.
D. The five amino acids that langurs and cows have in common in their lysozyme were present in the common ancestor of all mammals.
Answer: B
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Salamanders are amphibians with very interesting mating rituals. The males perform speciesspecific dances that attract females to mate
Male salamanders deposit spermatophores (mucus packets filled with sperm) on leaves, twigs, or the ground and guide females over them so females can take them up into their cloaca. Mating dances like this result in internal fertilization in many salamander species. Which of the following statements best explains why salamanders are not entirely terrestrial in spite of exhibiting internal fertilization in many species? A. Salamanders require water for gas exchange B. Salamanders simply lay their eggs near the water in which they live. C. Internal fertilization is the first necessary step towards non-dependence of water for reproduction. D. Salamanders do not produce amniotic eggs, therefore they require water for reproduction because eggs need protection from desiccation. E. Internal fertilization only occurs in species where reproduction does not require water. Salamanders simply lay their eggs near the water in which they live.
Korarchaeota ____
a. includes halophiles b. includes psychrophiles c. diverged very early in Archaean evolution d. includes halophiles and thermophiles e. diverged very late in Archaean evolution
Annual influenza vaccinations are important for all individuals because
A. the virus is stable so once the vaccine is administered, protection from antibodies is lifelong. B. the highly contagious nature of the virus means that transmission from a robust individual to those with a weaker immune system, such as the young or the elderly, is facilitated in crowded winter conditions. C. the oral-fecal transmission route makes it easy to pass to others. D. the vaccine prevents secondary infections in individuals with influenza.
How many phases are there in the eukaryotic cell cycle?
a. 1 b. 2 c. 3 d. 4 e. 5