What is the difference in the bonding between alpha-helix and beta sheets?
A. Sulfur bridges allow the spring like turns in alpha helices and van der Waals dispersion allows the folds in beta sheets.
B. Hydrogen bonding occurs between the amides of adjacent chains in the sheets instead of between the amides in different parts of the helices.
C. Hydrogen bonding always occurs in the alpha helices but only occurs in parallel beta sheets.
D. Hydrogen bonding between the amides only occurs in one of these two types of secondary structures.
Answer: B
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During which phase of meiosis will the homologous chromosomes pair up?
A. anaphase I B. prophase II C. telophase II D. metaphase I E. prophase I
Gap junctions are most plentiful in ____
a. smooth and cardiac muscle b. skeletal muscle
c. stomach and urinary bladder d. blood vessels e. brain and spinal cord
To attach a particular amino acid to the tRNA molecule that will transport it, an enzyme, an aminoacyl-tRNA synthetase, is required, along with ATP. Initially, the enzyme has an active site for ATP and another for the amino acid
, but it is not able to attach the tRNA. What must occur for the final attachment to occur? A) The ATP must first have to attach to the tRNA. B) The binding of the first two molecules must cause a 3-D change that opens another active site on the enzyme. C) The ATP must be hydrolyzed to allow the amino acid to bind to the synthetase. D) The tRNA molecule must alter its shape to be able to fit into the active site with the other two molecules. E) The end of the tRNA must be cleaved before it can have an attached amino acid.
Which of the following is NOT a necessary component of a "true" circulatory system?
A. blood or hemolymph B. blood vessels C. one or more hearts D. capillaries E. All of these choices are components of a true circulatory system.