What is hydrogen bonding?
The attraction between one molecule's relatively positive areas and another's relatively negative areas.
The repulsion between the positive and negative charges of two molecules.
The attraction between two nonpolar molecules.
The attraction between two ionic molecules.
The Correct Answer is A
Hydrogen bonding is an interaction involving a hydrogen atom located between a pair of other atoms having a high affinity for electrons.
One atom of the pair (the donor), generally a fluorine, nitrogen, or oxygen atom, is covalently bonded to a hydrogen atom, whose electrons it shares unequally; its high electron affinity causes the hydrogen to take on a slight positive charge.
The other atom of the pair (the acceptor), also typically F, N, or O, has an unshared electron pair, which gives it a slight negative charge.
Mainly through electrostatic attraction, the donor atom effectively shares its hydrogen with the acceptor atom, forming a bond.
Choice B) The repulsion between the positive and negative charges of two molecules is incorrect because hydrogen bonding involves attraction, not repulsion.
Choice C) The attraction between two nonpolar molecules is incorrect because hydrogen bonding involves polar molecules.
Choice D) The attraction between two ionic molecules is incorrect because hydrogen bonding involves polar molecules and not ionic molecules.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
In a well-designed experiment, all variables apart from the treatment should be kept constant between the control group and treatment group.
This means researchers can correctly measure the entire effect of the treatment without interference from confounding variables.
Choice B) Independent variable and dependent variable is incorrect because these are not groups but rather variables.
The independent variable is manipulated by the experimenters while the dependent variable is measured to see if it changes as a result of the manipulation.
Choice C) Experimental group and non-experimental group is incorrect because a non-experimental group is not a term used in experimental design.
The correct term for the group that does not receive the treatment is control group.
Choice D) High level and low level of the independent variable is incorrect because these are levels of the independent variable, not groups.
In an experiment, there can be multiple levels of the independent variable, but they are applied to different groups (e.g. control group, treatment group).
Correct Answer is C
Explanation
Immunologic memory is the hallmark of adaptive immunity.
Immunologic memory enables the host to mount a more rapid and efficient immune response upon subsequent exposure to the antigen.
Choice A is incorrect because rapid recruitment of immune cells to sites of infection and inflammation is a characteristic of innate immunity.
Choice B is incorrect because antigen-independent defense mechanisms are characteristic of innate immunity.
Choice D is incorrect because non-specific host-defence mechanisms are characteristic of innate immunity.
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