Which one of the following statements concerning protein folding in cells
is INCORRECT?
A. Ubiquitin ligase-mediated attachment of ubiquitin to a newly
synthesized polypeptide leads to hydrolysis (breakdown, degradation) of
that polypeptide by the proteasome.
B. Protein folding in cells is highly efficient with more than 95% of all
newly synthesized polypeptides folding into their native, fully functional
shapes.
C. The chaperone HSP70 has an ATP-dependent mechanism for
delaying the folding of a newly synthesized polypeptide.
D. The chaperone HSP70 can bind to a nascent polypeptide. -
ANSWER B. Protein folding in cells is highly efficient with more than
95% of all newly synthesized polypeptides folding into their native, fully
functional shapes.
Even with the assistance of numerous chaperones in protein folding,
approximately 30% of all newly synthesized polypeptides are misfolded
and tagged by a ubiquitin ligase with the short peptide ubiquitin, a tag
that promotes breakdown (degradation) of the polypeptide by the
proteasome.
Which one of the following statements concerning polypeptide(s) or
protein(s) is INCORRECT?
A. A protein is made up of one or more polypeptides.
B. The primary structure of a polypeptide determines where (along the
length of the polypeptide) secondary structures such as alpha-helices or
beta-sheets can form.
, C. Polypeptide synthesis involves addition of amino acid monomers only
at the C- (COOH-) terminus of the polypeptide.
D. The initial folding of a linear polypeptide is driven by hydrophobic
collapse where the nonpolar side chains are more likely to end up in the
interior region of the folded polypeptide. - ANSWER D. The initial
folding of a linear polypeptide is driven by hydrophobic collapse where
the nonpolar side chains are more likely to end up in the interior region
of the folded polypeptide.
The initial folding of a linear polypeptide is driven by hydrogen bond
formation between atoms of the polypeptide backbone to form alpha-
helices or beta-sheets, the secondary structure of a protein. Formation
of tertiary structure, driven by hydrophobic collapse, occurs later than
secondary structure formation, a more local phenomenon.
Which one of the following statements about enzymes and enzyme-
catalyzed chemical reactions is CORRECT?
A. Enzymes are always made of protein.
B. Enzymes often change shape when they bind their substrate(s).
C. Enzymes are typically promiscuous, e.g, an enzyme that catalyzes a
reaction involving a specific sugar can typically catalyzes reactions with
many other types of sugars.
D. Spontaneous chemical reactions are relatively fast. - ANSWER B.
Enzymes often change shape when they bind their substrate(s).
Which one of the following statements concerning enzyme regulation is
FALSE?
A. Most enzymes regulated by allosteric mechanisms contain one or
more polypeptides (subunits).
B. The allosteric site is never the same as the active site.
C. Many metabolic pathways are regulated by the binding of their end
product to an enzyme that acts in an early step of the pathway, a type of
feedback inhibition.
D. ATP can be a substrate at the active site of an enzyme or it can bind
to the allosteric site as an inhibitor. - ANSWER B. The allosteric site is
never the same as the active site.
is INCORRECT?
A. Ubiquitin ligase-mediated attachment of ubiquitin to a newly
synthesized polypeptide leads to hydrolysis (breakdown, degradation) of
that polypeptide by the proteasome.
B. Protein folding in cells is highly efficient with more than 95% of all
newly synthesized polypeptides folding into their native, fully functional
shapes.
C. The chaperone HSP70 has an ATP-dependent mechanism for
delaying the folding of a newly synthesized polypeptide.
D. The chaperone HSP70 can bind to a nascent polypeptide. -
ANSWER B. Protein folding in cells is highly efficient with more than
95% of all newly synthesized polypeptides folding into their native, fully
functional shapes.
Even with the assistance of numerous chaperones in protein folding,
approximately 30% of all newly synthesized polypeptides are misfolded
and tagged by a ubiquitin ligase with the short peptide ubiquitin, a tag
that promotes breakdown (degradation) of the polypeptide by the
proteasome.
Which one of the following statements concerning polypeptide(s) or
protein(s) is INCORRECT?
A. A protein is made up of one or more polypeptides.
B. The primary structure of a polypeptide determines where (along the
length of the polypeptide) secondary structures such as alpha-helices or
beta-sheets can form.
, C. Polypeptide synthesis involves addition of amino acid monomers only
at the C- (COOH-) terminus of the polypeptide.
D. The initial folding of a linear polypeptide is driven by hydrophobic
collapse where the nonpolar side chains are more likely to end up in the
interior region of the folded polypeptide. - ANSWER D. The initial
folding of a linear polypeptide is driven by hydrophobic collapse where
the nonpolar side chains are more likely to end up in the interior region
of the folded polypeptide.
The initial folding of a linear polypeptide is driven by hydrogen bond
formation between atoms of the polypeptide backbone to form alpha-
helices or beta-sheets, the secondary structure of a protein. Formation
of tertiary structure, driven by hydrophobic collapse, occurs later than
secondary structure formation, a more local phenomenon.
Which one of the following statements about enzymes and enzyme-
catalyzed chemical reactions is CORRECT?
A. Enzymes are always made of protein.
B. Enzymes often change shape when they bind their substrate(s).
C. Enzymes are typically promiscuous, e.g, an enzyme that catalyzes a
reaction involving a specific sugar can typically catalyzes reactions with
many other types of sugars.
D. Spontaneous chemical reactions are relatively fast. - ANSWER B.
Enzymes often change shape when they bind their substrate(s).
Which one of the following statements concerning enzyme regulation is
FALSE?
A. Most enzymes regulated by allosteric mechanisms contain one or
more polypeptides (subunits).
B. The allosteric site is never the same as the active site.
C. Many metabolic pathways are regulated by the binding of their end
product to an enzyme that acts in an early step of the pathway, a type of
feedback inhibition.
D. ATP can be a substrate at the active site of an enzyme or it can bind
to the allosteric site as an inhibitor. - ANSWER B. The allosteric site is
never the same as the active site.
