Chapter 4 Need to Know

Carbon's atomic number is 6. This means that it has __________ electrons. After completing the first energy level, carbon has __________ valence electrons and can form __________ bonds.

6; 4; 4

Which chemical group is most likely to be responsible for an organic molecule behaving as a base?

Amino

Which of the following is found in all amino acids?

Both -COOH and -NH2 (All amino acids contain at least one carboxyl functional group and one amino functional group. In addition, it may contain one or more of the other functional groups.)

In the pharmaceutical industry, two enantiomers of a drug __________.

May not be equally effective

Pharmaceutical companies are selling close to $200 billion worth of single-enantiomer drugs. Why might it be important to use only one form of an enantiomer?

One enantiomer may provide an effective treatment whereas the other may be ineffective or even toxic.

Which of the following molecules is a weak acid?

R-NH2 R-OH None of the listed responses is correct. ***R-COOH*** R-SH

What are the six most important chemical elements of life?

SPONCH; sulfer, phosphate, oxygen, nitrogen, hydrogen

The carbon atom is tetravalent; this means that __________.

a carbon atom can complete its valence shell by forming four covalent bonds

Stanley Miller's experiments were significant because he demonstrated that __________.

a variety of simple organic compounds could be spontaneously synthesized from components in Earth's primitive atmosphere

In Miller's 1953 laboratory experiment, __________.

abiotic compounds cycled through the apparatus and were sampled for organic compounds

The carbon skeleton can vary in all of the following except __________.

branching; presence of rings; double bond position; length; ***lacking hydrogen atoms***

Molecules that contain only carbon and hydrogen are __________.

called hydrocarbons

The chemical group that acts as an acid is the __________.

carboxyl group (-COOH)

The chemical group that helps stabilize protein structure is the __________.

sulfhydryl group (-SH)

Structural isomers have __________.

the same molecular formula but different covalent arrangements of their carbon skeletons

Which of the following molecules is a weak base?

****R-NH2**** R-OH R-SH None of the listed responses is correct. R-COOH

Which element is always associated with organic chemistry?

Carbon

Carbon has 6 electrons, with 2 in the first electron shell and 4 in the second shell; thus, it has 4 valence electrons in a shell that can hold up to 8 electrons. A carbon atom usually completes its valence shell by sharing its 4 electrons with other atoms so that 8 electrons are present. Each pair of shared electrons constitutes a covalent bond. In organic molecules, carbon usually forms single or double covalent bonds. Each carbon atom acts as an intersection point from which a molecule can branch off in as many as four directions. This enables carbon to form large, complex molecules.

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Inorganic carbon such as CO2 differs from organic carbon because __________.

organic carbon always has a hydrogen atom covalently attached to it

When three phosphate groups are covalently attached to adenosine, __________ is formed.

ATP

What is ATP's importance in the cell?

ATP stores the potential to react with water, thereby removing a phosphate group and releasing energy for cellular processes.

Which of the following are properties of hydrocarbons?

Hydrophobic, nonpolar, and a good source of stored energy

Which chemical group is most likely to be responsible for an organic molecule behaving as a base?

Hydroxyl Carbonyl Carboxyl ***Amino*** Phosphate

In the carbon dioxide molecule (CO2), a single carbon atom is joined to two atoms of oxygen by double covalent bonds. The structural formula for CO2 is shown here: O=C=O. Each line in a structural formula represents a pair of shared electrons. Thus, the two double bonds in CO2 have the same number of shared electrons as four single bonds. The arrangement completes the valence shells of all atoms in the molecule. Because CO2 is a very simple molecule and lacks hydrogen, it is often considered inorganic even though it contains carbon. Whether we call CO2 organic or inorganic, however, it is clearly important to the living world as the source of carbon for all organic molecules in organisms.

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Choose the pair of terms that completes this sentence about functional groups in organic chemistry: Carboxyl is to __________ as __________ is to base.

acid; amino

Although the structures of the functional groups that are most important to life vary, they share one thing in common: They __________.

all are hydrophilic and increase the organic compound's water solubility

Biologically important chemical groups include all of the following except __________.

amine group (-NH2) sulfhydryl group (-SH) ***water (H2O)*** phosphate group (-PO3-2) carboxyl group (-COOH)

When a double bond joins two carbon atoms, __________ can form.

cis-trans isomers

The chemical group that is involved in regulating DNA is the __________.

methyl group (-CH3)

Enantiomers are __________.

mirror-image isomers of a molecule