In the watson-crick model of dna structure: a. nitrogenous bases are covalently attached to carbon 1' of deoxyribose t can form three hydrogen bonds with either g or c in the opposite strand. b. the distance between the sugar backbone of the two strands is just large enough to accommodate either two purines or two pyrimidines. c. both strands run in the same direction, 3' -> 5'; they are parallel. d. phosphate groups project toward the middle of the helix, where they are protected from interaction with water.

Molecular models of two different substances are shown below. in the molecule on the left, the oxygen atom pulls on electrons more strongly than the hydrogen atoms. in the molecule on the right, the two oxygen atoms pull on the shared electrons with the same strength. water molecule, h, o oxygen molecule, oz when the two substances are put in the same container, they do not attract each other. why does this happen? a. they both contain oxygen. b. one is polar and one is nonpolar. c . they are both polar. d. they contain different elements.

Apart of an ecosystem that can restrict the growth of a population is referred to as

1) what three conditions must be present for minerals to form through natural processes? 2) why are minerals considered inorganic substances? 3) how do oxides differ from other minerals that contain oxygen atoms? 4) how is a sulfide different from a sulfate? what makes native elements unique?