Intro to Molecular Cell Biology Test Bank Chapter 4 well illustrated study guide

Intro to Molecular Cell Biology Test Bank Chapter 4

True or false:

Generally, the total number of nonpolar amino acids has a greater affect on protein structure than the
exact order of amino acids in a polypep de chain. - False. The order in which amino acids are linked is
unique for each protein and is the most important factor in determining the overall protein factor.



True or False:

The "polypep de backbone" refers to all atoms in a polypep de chain, except for those that form the
pep de bonds. - False. Pep de bonds are planar amide bonds

that are central to the polypep de backbone

forma on. The atoms in the amino acid side

chains are not considered to be part of the

backbone.



True or False:

The chemical proper es of amino acid side chains include charged, uncharged polar and nonpolar. - True



True or False: The rela ve distribu on of polar and nonpolar amino acids in a folded protein is
determined largely by hydrophobic interac ons, which favor the clustering of nonpolar side chains in the
interior. - True



Polypep des are synthesized from amino acid building blocks. The condensa on reac on between the
growing polypep de chain and the next amino acid to be added involves the loss of
____________________.

(a) a water molecule

(b) an amino group

(c) a carbon atom

(d) a carboxyl acid group - (a) a water molecule

, The varia ons in the physical charactersi cs between different proteins are influenced by the overall
amino acid composi ons, but even more important is the unique amino acid ___________________.

(a) number

(b) sequence

(c) bond

(d) orienta on - (b) sequence



Fully folded proteins typically have polar side chains on their surfaces, where electrosta c a rac ons
and hydrogen bonds can form between the polar group on the amino acid and the polar molecules in
the solvent. In contrast, some proteins have a polar side chain in their hydrophobic interior. Which of the
following would not occur to help accommodate an internal, polar side chain?

(a) A hydrogen bond forms between two polar chains

(b) A hydrogen bond forms between a polar side chain and the protein backbone.

(c) A hydrogen bond forms between a polar side chain and an aroma c side chain.

(d) Hydrogen bonds form between polar side chains and a buried water molecule. - (c) A hydrogen bond
forms between a polar side chain and the protein backbone.



To study how proteins fold, scien sts must be able to purify the protein of interest, use solvents to
denature the folded protein, and observe the process of refolding at successive me points. What is the
effect of the solvents used in the denatura on process?

(a) the solvents break all covalent interac ons.

(b) the solvents break all noncovalent interac ons

(c) the solvents break some of the noncovalent interac ons, resul ng in a misfolded protein.

(d) the solvents create a new protein conforma on. - (b) the solvents break all noncovalent interac ons



Which of the following statements is true?

(a) Pep de bonds are the only covalent bonds that can link together two amino acids in proteins.

(b) The polypep de backbone is free to rotate about each pep de bond.

(c) Nonpolar amino acids tends to be found in the interior of proteins

(d) The sequence of the atoms in the polypep de backbone varies between different proteins. - (c)
nonpolar amino acids tend to be found in the interior of proteins