The stomach differs from the small intestine in that it
A) secretes enzymes.
B) produces enzymes that work best at a low pH.
C) secretes hormones that travel through the bloodstream.
D) has tiny projections called villi that are folded into microvilli.
E) does not secrete mucus.
B
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The disease known as dengue hemorrhagic fever is actually
A) a hyperimmune response to reinfection with the dengue virus. B) an immediate immune reaction to the initial infection with the dengue virus. C) an antibody-antigen complex reaction. D) the result of co-infection with other arboviruses. E) the chronic carrier state of the dengue virus.
Which of the following would NOT be part of the germ tube?
A. tube cell nucleus B. two sperm cells C. pollen sporopollenin wall D. pectin precursors E. cell membrane
Certain small towns in the western United States have remained isolated since their settlement many years ago. Some alleles are more common in these communities as compared to the rest of the US population. This difference is a result of
A. disrupting selection. B. the founder effect. C. directional selection. D. the Hardy-Weinberg principle. E. artificial selection.
The comet exploring Rosetta spacecraft, Philae, reports back the presence of single-celled organisms that resemble bacteria found on the comet C-G. A module from the spacecraft containing a sample of the organism is rocketed back to earth
Amazingly, the comet organism can be grown in the lab. It is determined that DNA and RNA and proteins arepresent in the comet organism, but that four of the nitrogenous bases are different from terrestrial nucleotides. The comet organism's nitrogenous bases are named A, B, C, and D. Comet organism proteinswere found to contain only the 20 amino acids regularly found as components of terrestrial proteins. You are askedto decipher the genetic code of this comet organism. You synthesize three polyribonucleotides consisting of various combinations of A, B, and Cnitrogenous bases,and determine the amino acid sequence of any proteins synthesizedduring comet-organism cell-free in vitro translation. The results are shown in the table below: Polynucleotide sequence Amino acid sequence of polypeptide(s) 5' BCBCBCBCBCBC….. 3' …..GLY-ILE-GLY-ILE-GLY-ILE….. 5' BBCBBCBBCBBC….. 3 ' …..GLY-GLY-GLY-GLY-GLY….. …..ASN- ASN- ASN- ASN- ASN….. …..TYR-TYR-TYR-TYR-TYR….. 5'ABBCABBCABBCABBC….. 3' …..LYS-THR-VAL-TYR-LYS-THR-VAL-TYR….. If the genetic code of the comet organism is a triplet, nonoverlapping code with no commas, what is the codon for asparagine? A. BBC B. BCB C. CBB D. BBB