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A covalent chemical bond is one in which

outer-shell electrons of two atoms are shared so as to satisfactorily fill the outer electron shells of both atoms.


What do atoms form when they share electron pairs?



If an atom of sulfur (atomic number 16) were allowed to react with atoms of hydrogen (atomic number 1), which molecules would be formed



When two atoms are equally electronegative, they will interact to form

nonpolar covalent bonds.


What results from an unequal sharing of electrons between atoms?

a polar covalent bond


Which of the following molecules contains the strongest polar covalent bond?



What is the difference between covalent bonds and ionic bonds?

Covalent bonds involve the sharing of electrons between atoms, and ionic bonds involve the electrical attraction between atoms.


What kind of a bond does NH4+ form with Cl- to make ammonium chloride salt (NH4Cl)?



In a single molecule of water, the two hydrogen atoms are bonded to a single oxygen atom by

polar covalent bonds.


The slight negative charge at one end of one water molecule is attracted to the slight positive charge of another water molecule. What is this attraction called?

a hydrogen bond


An example of a hydrogen bond is the bond between

the H of one water molecule and the O of another water molecule.


Water is able to form hydrogen bonds because

the bonds that hold together the atoms in a water molecule are polar covalent bonds.


Which of the following is possible due to the high surface tension of water?

A water strider can walk across the surface of a small pond.


Which of the following is true when an ice cube cools a drink?

Kinetic energy in the drink decreases.


Hydrophobic substances such as vegetable oil are

nonpolar substances that repel water molecules.


If the pH of a solution is increased from pH 5 to pH 7, it means that the

concentration of OH- is 100 times greater than what it was at pH 5.


Which property of the carbon atom gives it compatibility with a greater number of different elements than any other type of atom?

Carbon has a valence of 4.


How many electron pairs does carbon share in order to complete its valence shell?



Which of the following is (are) true about the carbon atoms present in all organic molecules?

They were incorporated into organic molecules by plants.
They were processed into sugars through photosynthesis.
They are ultimately derived from carbon dioxide.


What is the reason why hydrocarbons are not soluble in water?

The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages.


A compound contains hydroxyl groups as its predominant functional group. Which of the following statements is true concerning this compound?

It should dissolve in water.


The tertiary structure of a protein is the

unique three-dimensional shape of the fully folded polypeptide.


A strong covalent bond between amino acids that functions in maintaining a polypeptide's specific three-dimensional shape is a (an)

disulfide bond.


At which level of protein structure are interactions between the side chains (R groups. most important?



The R group or side chain of the amino acid serine is –CH2-OH. The R group or side chain of the amino acid alanine is –CH3. Where would you expect to find these amino acids in a globular protein in aqueous solution?

Alanine would be in the interior, and serine would be on the exterior of the globular protein.


The globular protein transthyretin results from the aggregation of four polypeptide subunits. Each of the subunits is a polypeptide chain with an helix region. Which structure(s) must the transthyretin protein have?

primary, secondary, tertiary, and quaternary structure


What would be an unexpected consequence of changing one amino acid in a protein consisting of 325 amino acids?

The primary structure of the protein would be changed.
The tertiary structure of the protein might be changed.
The biological activity or function of the protein might be altered.


Large organic molecules are usually assembled by polymerization of a few kinds of simple subunits. Which of the following is an exception to this statement?

a steroid


The element nitrogen is present in all of the following except