Water is a strongly polar molecule. How does it cross the plasma membrane?
What will be an ideal response?
ANSWER: Water molecules are small enough to slip through spaces transiently created between the
hydrocarbon tails of phospholipid molecules as they flex and rotate in the fluid bilayer. This
type of water movement is relatively slow, however. It can also pass through aquaporins,
channels specific for water.
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If a short sequence of DNA is 5' AATTGCCGT 3', its complement is
A. 5' AAAACGCCA 3'. B. 5' TTAACGGCA 3'. C. 3' TTAAGCCGA 5'. D. 3' TTAACGGCA 5'. E. 3' TTAACGGCT 5'.
Which of the following worms lacks a digestive system?
a. filariae b. tapeworms c. earthworms d. roundworms e. leeches
Which of the following is an evolutionary history of the relationships between various species?
a. biology b. systema c. taxonomic filing d. phylogeny
About how many SNPs exists in the human genome?
a. 1 million b. 3 million c. 30 million d. 1 billion e. 3 billion