ions

Ex.

When a very electronegative atom strips a valence electron away from its partner, ions form.

In some cases, two atoms are so unequal in their attraction for valence electrons that the more electronegative atom strips an electron completely away from its partner. The two resulting oppositely charged atoms (or molecules) are called ions. A positively charged ion is called a cation, while a negatively charged ion is called an anion. Because of their opposite charges, cations and anions attract each other; this attraction is called an ionic bond. Note that the transfer of an electron is not, by itself, the formation of a bond; rather, it allows a bond to form because it results in two ions of opposite charge. Any two ions of opposite charge can form an ionic bond. The ions do not need to have acquired their charge by an electron transfer with each other.

“Hydrogen bonds” is incorrect because these are weak chemical bonds where there is an attraction between a hydrogen atom and an electronegative atom.

“Van der Waals interactions” is incorrect because this is a weak chemical reaction that occurs only when atoms and molecules are very close together.

“Covalent bonds” is incorrect because this is the sharing of a pair of valence electrons by two atoms.

“Polar covalent bonds” is incorrect because this is the sharing of a pair of valence electrons by two atoms, where one of the atoms is strongly electronegative.

can produce similar effects as the naturally occurring molecules

Ex.

Molecular mimics can produce similar effects as the naturally occurring molecules.

Molecular shape is crucial: It determines how biological molecules recognize and respond to one another with specificity. Biological molecules often bind temporarily to each other by forming weak bonds, but only if their shapes are complementary. Consider the effects of opiates, drugs such as morphine and heroin that are derived from opium. Opiates relieve pain and alter mood by weakly binding to specific receptor molecules on the surfaces of brain cells. Why would brain cells carry receptors for opiates, compounds that are not made by the body? In 1975, the discovery of endorphins answered this question. Endorphins are signaling molecules made by the pituitary gland that bind to the receptors, relieving pain and producing euphoria during times of stress, such as intense exercise. Opiates have shapes similar to that of endorphins and mimic them by binding to endorphin receptors in the brain. That is why opiates and endorphins have similar effects. The role of molecular shape in brain chemistry illustrates how biological organization leads to a match between structure and function, one of biology’s unifying themes.

“Are identical to naturally occurring molecules that are produced by an organism” is incorrect because only a portion of the molecule is identical to the naturally occurring molecule.

“Destroy the effect of the naturally occurring molecules” is incorrect because the mimic mimics the effect of the naturally occurring molecule.

“Are the receptors for the naturally occurring molecules” is incorrect because the mimic binds to the receptor of the naturally occurring molecules and is not the receptor.

the transfer of valence electrons results in a completed valence shell for each ion

Ex.

In ionic interactions, the transfer of valence electrons results in a completed valence shell for each ion.

When two atoms are very unequal in their attraction for valence electrons, the more electronegative atom strips an electron completely away from its partner. The two resulting oppositely charged atoms (or molecules) are called ions. A positively charged ion is called a cation, while a negatively charged ion is called an anion. Because of their opposite charges, cations and anions attract each other; this attraction is called an ionic bond. Note that the transfer of an electron is not, by itself, the formation of a bond; rather, it allows a bond to form because it results in two ions of opposite charge. Any two ions of opposite charge can form an ionic bond. The ions do not need to have acquired their charge by an electron transfer with each other.

“The anion always loses an electron” is incorrect because the anion always gains an electron.

“The cation always gains an electron” is incorrect because the cation always loses an electron.

“There is always the equal sharing of electrons” is incorrect because this is a covalent bond.

“There are always weak interactions in a dry salt crystal” is incorrect because dry salt crystals always have strong interactions.