Which of the following does NOT occur in the first trimester?
a. formation of a heart
b. disappearance of the tail
c. formation of internal organs
d. detection of movement of the fetus
e. segmentation and development of somites
D
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Which of the following statements is TRUE of membrane phospholipids?
A. The hydrophilic head groups face the interior portion of the membrane. B. The hydrophobic tail groups face the exterior portion of the membrane. C. They spontaneously flip-flop from one side of the membrane to the other. D. They freely move laterally within the membrane. E. They rarely flip-flop across or move laterally within the membrane.
Bulk flow in the phloem tissue is mostly downward whereas bulk flow in xylem is mostly:
A. sideways B. also downward C. very little bulk flow occurs in xylem D. flow of sugars E. upward
What is the correct sequence of events in cross-bridge cycling?
A. Myosin cross-bridge binds to actin, the powerstroke moves the thin filament relative to the thick filament, ATP binds to myosin and cross-bridge detachment occurs, ATP is hydrolyzed and the myosin head is "cocked" B. The powerstroke moves the thin filament relative to the thick filament, myosin cross-bridge binds to actin, ATP binds to myosin and cross-bridge detachment occurs, ATP is hydrolyzed and the myosin head is "cocked" C. Myosin cross-bridge binds to actin, ATP is hydrolyzed and the myosin head is "cocked," the powerstroke moves the thin filament relative to the thick filament, ATP binds to myosin and cross-bridge detachment occurs D. Myosin cross-bridge binds to actin, ATP binds to myosin and cross-bridge detachment occurs, the powerstroke moves the thin filament relative to the thick filament, ATP is hydrolyzed and the myosin head is "cocked" E. These events can occur in any sequence without affecting muscle function.
What is one of the similarities between prokaryotic and eukaryotic cell division?
A) DNA is unwound and duplicated by the same process. B) At the end of cell division, nuclear membranes form around the chromosomes. C) One cell divides into four cells. D) Microtubules separate the chromosomes.