These skin cells fight infections: ________
A) fibroblasts B) macrophages C) melanocytes D) neuroglia
Answer: B
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Secondary protein structure is dependent on
a. hydrophobic interactions. b. hydrogen bonds between two amino acids. c. covalent linkages between carbons and nitrogens of adjacent amino acids. d. covalent linkages between carbons and oxygens of adjacent amino acids. e. all of these.
Based on the data in Table 18-1, which of the following primates has the most recent common ancestor with humans?
a. rhesus monkey
b. gibbon
c. tarsier
d. gorilla
e. orangutan
When bacteria are inoculated into a new sterile nutrient broth, their numbers don't begin to increase immediately. Instead, there is a lag phase that may last for an hour or even several days. Why don't bacterial numbers increase immediately?
a. There are not enough nutrients for the bacteria to grow, and growth is delayed until there are some dead cells to cannibalize. b. The bacteria have to establish a biofilm before their numbers can increase. c. The bacteria must adjust to the nutrient content in the new medium, synthesizing necessary amino acids, growth factors, and enzymes. d. The medium contains inhibitors that prohibit rapid growth of the bacteria, and these must be inactivated before bacterial numbers will increase.
Evidence in support of the endosymbiotic theory includes
A) linear DNA in mitochondria and chloroplasts. B) a single membrane enclosing the mitochondria and chloroplasts. C) the presence of 70S ribosomes in mitochondria and chloroplasts. D) the presence of 70S ribosomes in mitochondria and chloroplasts and a single membrane enclosing the mitochondria and chloroplasts linear DNA in mitochondria and chloroplasts. E) the presence of 70S ribosomes in mitochondria and chloroplasts and a single membrane enclosing the mitochondria and chloroplasts.