AP Biology : Understanding Essential Properties of Carbon

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #1 : Understanding Essential Properties Of Carbon

Which of the following properties of carbon is particularly important to its biological properties?

Possible Answers:

Ability to generate long chains

Ability to form single bonds with up to four different atoms

All of these answers

Ability to make aromatic compounds

Correct answer:

All of these answers

Explanation:

Carbon is phenomenally important to life as we understand it. The ability to form bonds with up to four different atoms gives carbon an incredible chemical diversity, and allows for carbon to make long chains and aromatic compounds. The ability to make long chains and aromatic compounds accounts for the formation of nucleic acids, proteins, and lipids (macromolecules that are absolutely essential to life). Binding properties of carbon also relate to the structure and orientation of biological compounds, which are important aspects of organic chemistry.

Example Question #2 : Understanding Essential Properties Of Carbon

How many bonds can a carbon atom make?

Possible Answers:

Five

Two 

Three

Four

One

Correct answer:

Four

Explanation:

In its ground state carbon has four valence electrons, two its full s subshell and two in a partially filled p subshell. Normally, this would indicate that carbon forms two bonds, since only two of the electrons are in orbitals that are not already paired. Carbon, however, is able to form hybrid orbitals by combining the three p orbitals and one s orbital to form four identical sp3 orbitals, each containing one electron. This means that carbon can form four bonds, allowing it to achieve a stable octet.

For biology, the important note is that carbon can make four bonds. Organic chemistry is the study of carbon and how these bonds function to create organic and biological materials.

Example Question #3 : Understanding Essential Properties Of Carbon

What property of carbon most contributes to its ability to form such a diverse range of molecules?

Possible Answers:

It tends to form ionic bonds in organic molecules

It can form a quadruple bond

It has a small atomic mass

It has four valance electrons

It is magnetic

Correct answer:

It has four valance electrons

Explanation:

Carbon has four valance electrons, allowing it to form a wide range of bonds with other atoms.

When carbon bonds to four separate substituents, it forms a tetrahedral structure. Because of its ability to hybridize orbitals, carbon can also bond to three substituents by forming a double bond, or to two substituents via two double bonds or the combination of a single bond and a triple bond. This variability in molecular bonding and shape allows carbon to exist in numerous compounds, exhibiting a number of different properties and functions.

Carbon is incapable of forming a quadruple bond, and it is not magnetic. Though carbon has a relatively low atomic mass, one would expect hydrogen to be the most relevant element if low mass was the most pertinent property of carbon. Carbon can form ionic bonds (generally with metals), but is most commonly found in organic molecules where it forms covalent bonds.

Example Question #4 : Understanding Essential Properties Of Carbon

A substance that cannot be broken down by chemical reactions into other substances is __________.

Possible Answers:

a compound 

a subatomic particle

an element

a unit of matter

Correct answer:

an element

Explanation:

An element cannot be broken down into other substances. Compounds consist of two or more elements and thus can be broken down. Matter is simply anything that takes up space and has mass; both elements and compounds are matter. Subatomic particles are the building blocks of atoms. Though atoms are the units that make up elements and are the smallest units to have the properties of an element, subatomic particles themselves do not display characteristic of an element.

Example Question #5 : Understanding Essential Properties Of Carbon

Which statement best describes why life on earth is carbon based? 

Possible Answers:

The relationship between carbon and water

The electronegativity of carbon

The relative ratio of other elements to carbon

Abundance of carbon

Its bonding versatility

Correct answer:

Its bonding versatility

Explanation:

Life is "carbon-based" or predominantly carbon because it can form stable bonds with itself, but also with a variety of other types of elements. Electronegativity increases from left to right on the periodic table, but also from bottom to top. While carbon is relatively high and right on the periodic chart, there are still elements like oxygen or fluorine (the most electronegative) that have a great pull for electrons. While carbon makes up a lot of the universe, it pales in comparison to hydrogen which is the most common element (three fourths of the mass of our universe). Therefore ratios do not matter. The polar and nonpolar nature of molecules are important for the functions of life (like membranes), but were it not for the bonding of carbon to itself, the nonpolar molecules would not be able to form. Thus, its bonding versatility is the main reason for life being carbon based.

Example Question #6 : Understanding Essential Properties Of Carbon

The chemical properties of which of the following elements are most similar to carbon?

Possible Answers:

Nitrogen

Oxygen

Iron

Silicon

Zinc

Correct answer:

Silicon

Explanation:

The chemical properties of an element are, in a large part, determined by the number of bonds that element can form with other elements. Silicon, like carbon, can form four bonds with other elements, and thus is the most similar. This can easily be seen on a periodic table as elements with similar properties are grouped together in the same column. Note that these similarities arise from having the same number of valence electrons. 

Example Question #2 : Understanding Essential Properties Of Carbon

What is the best description for isotopes of elements?

Possible Answers:

Elements that have the same number of electrons and the same number of neutrons.

Elements that have different numbers of electrons.

Elements that have different numbers of protons and different numbers of neutrons.

The same elements that have the same number of electrons and different numbers of neutrons.

Correct answer:

The same elements that have the same number of electrons and different numbers of neutrons.

Explanation:

Isotopes are the same element that have the same number of protons and electrons.  The difference is in their atomic weight because they have different numbers of neutrons.

Example Question #8 : Understanding Essential Properties Of Carbon

All of the following are carbohydrates except __________.

Possible Answers:

glucose

starch

glycogen

amino acids

Correct answer:

amino acids

Explanation:

Carbohydrates include the monosaccharide glucose and polysaccharides starch and glycogen.  Amino acids contain nitrogen and are the building blocks of polypeptides.

Example Question #9 : Understanding Essential Properties Of Carbon

What is the main way in which carbon dioxide is altered in the bloodstream?

Possible Answers:

Carbon dioxide is transported as a carboxyl group in the bloodstream

Carbon dioxide is bound to hemoglobin in the bloodstream

Carbon dioxide combines with water in the bloodstream to make carbonic acid

Carbon dioxide turns into sodium bicarbonate in the bloodstream

Correct answer:

Carbon dioxide combines with water in the bloodstream to make carbonic acid

Explanation:

Carbon dioxide is not very soluble in water, so it is carried in the blood almost exclusively as carbonic acid. While some carbon dioxide is bound to hemoglobin, the majority of it is carried in the blood as the bicarbonate ion, which is the blood's main buffer. Note the following chemical equilibria:

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