BIO 112 Chapter 3

Side chains of amino acids ________.

• are all nonpolar

• are nonpolar if they contain N or S

• are all polar

• may be polar or nonpolar

Which one of the following is NOT a component of each monomer used to make proteins?

• A phosphorus atom, P

• An amino functional group, NH2

• A side chain, R

• A carboxyl group, COOH

What component of amino acid structure varies among different amino acids?

• The long carbon-hydrogen tails of the molecule

• The presence of a central C atom

• The components of the R-group

• The glycerol molecule that forms the backbone of the amino acid

At about pH 7 in most cells, what happens to the amino group on an amino acid?

• It acts as a base and gains a proton, giving it a positive charge.

• It acts as an acid and loses a proton, giving it a negative charge.

• It is reduced and tends to act as an electron donor in redox reactions.

• It remains neutral, like water, and does not have a charge.

At about pH 7 in most cells, what happens to the carboxyl group on an amino acid?

• It acts as a base and gains a proton, giving it a positive charge.

• It acts as an acid and loses a proton, giving it a negative charge.

• It is oxidized and tends to act as an electron acceptor in redox reactions.

• It remains neutral, like water, and does not have a charge.

Why are polymerization reactions endergonic? Polymerization reactions ________.

• A) reduce entropy

• B) release heat, making the reactant monomers move faster

• C) release energy

• D) are at equilibrium

Which of the following involves an increase in entropy?

• Hydrolysis

• Reactions that join monomers

• Polymerization

• Chemical evolution

Suppose you discovered a new amino acid. Its R-group contains only hydrogen and carbon atoms. Predict the behavior of this amino acid.

• It is hydrophobic.

• It is hydrophilic.

• Relative to the amino acids found in organisms, its interactions with water will be intermediate.

• Relative to the amino acids found in organisms, its interactions with water will be very high.

A peptide bond __________.

• A) forms between the functional R-groups of different amino acids

• B) forms between the central carbon and the amino R-group of a single amino acid

• C) forms the primary structure of proteins

• D) does not play a role in maintaining the tertiary structure of proteins

The bonding of two amino acid molecules to form a larger molecule requires the __________.

• release of a water molecule

• release of a carbon dioxide molecule

• addition of a carbon dioxide molecule

• addition of a water molecule

• addition of a water molecule and a carbon dioxide molecule