NEW
Font size
WorksheetsBiochemistry Review
Total questions: 70
Worksheet time: 35mins
In 1953, Urey and Miller carried out an experiment in which they subjected a mixture of H2O, CH4, NH3, and H2 to electrical discharges. Which of the following were among the products?
proteins
amino acids
nucleic acids
ribosomes
all of the above
Which arrow points at a phosphate ester bond?
A
B
C
D
E
Which arrow points at a glycosidic bond?
A
B
C
D
E
A reaction with a ______ ΔH and a ______ ΔS will never be spontaneous.
positive, positive
positive, negative
negative, positive
negative, negative
none of the above
A spontaneous process
occurs without the addition of free energy.
has a ΔG<0.
is exergonic
is all of the above
is none of the above
Enzymes accelerate biochemical reactions by
decreasing the ΔG for the reactions.
increasing the ΔG for the reactions.
establishing a ‘closed system’ for each reaction.
promoting reaction pathways associated with a positive ΔG.
providing a more favorable pathway for the reactions.
The strongest noncovalent interactions are
ionic interactions.
hydrogen bonds.
dipole-dipole interactions.
London dispersion forces.
van der Waals forces.
Urea is a water-soluble product of nitrogen metabolism. How many hydrogen bonds can one urea molecule donate to surrounding water molecules?
2
3
4
5
6
Amphiphilic molecules
have both oxidizing and reducing groups.
are micelles.
have chromophores in two different wavelength regions.
have both acidic and basic groups.
have both hydrophilic and hydrophobic groups.
Which of the following is the best explanation for the hydrophobic effect?
It is caused by an affinity of hydrophobic groups for each other.
It is caused by the affinity of water for hydrophobic groups.
It is an entropic effect, caused by the desire of water molecules to increase their entropy by forming highly ordered structures around the hydrophobic groups.
It is an entropic effect, caused by the desire of water molecules to increase their entropy by excluding hydrophobic groups, which they must otherwise surround with highly ordered structures.
It is an entropic effect caused by the desire of hydrophobic groups to increase their entropy by associating with other hydrophobic groups.
The capacity of a buffer to resist changes in pH upon addition of protons or hydroxide ions depends on
the pKa of the weak acid in the buffer.
the pH of the buffer.
the total concentration of the weak acid and its conjugate base in the buffer.
all of the above
none of the above
What group is attached to the pyrimidine ring in thymine and is not present in uracil?
ribose
—CH3
—NH2
deoxyribose
none of the above
By convention, the sequence of nucleotide residues in a nucleic acid is written ___________ starting with the ____ end.
left to right; 3'
right to left; 3'
left to right; 5'
right to left; 3'
top to bottom; 3'
Chargaff’s rules state that:
The amount of guanine plus cytosine in mammalian genomes varies from about 39 to 46%.
DNA is always double stranded and RNA is always single stranded.
DNA contains two grooves, a major groove and a minor groove.
In DNA the number of adenine residues is identical to the number of thymine residues and the number of guanine residues is identical to the number of cytosine residues.
DNA contains two strands that run in opposite directions.
Knowledge about the tautomeric forms of the bases of nucleic acids is needed
to understand H-bonding between the complementary bases
to understand how the bases are linked to ribose.
to understand how bases are linked to deoxyribose.
to understand the ability of nucleotides to act as energy carriers.
to distinguish the 5’-end of a DNA strand from the 3’-end.
Nucleotides in a DNA molecule are linked together through
glycosidic bonds.
amide linkages.
hydrogen bonds.
phosphoanhydride bonds.
phosphodiester bonds.
Genomic DNA is ______, resulting in the production of _________.
transcribed; mRNA
translated; tRNA
transcribed; protein
translated; protein
translated; rRNA
Small circular DNA molecules used to carry foreign DNA fragments are called ________.
mRNAs
bacteriophage
clones
plasmids
nucleotides
About half of the 20 amino acids are called essential because
they are essential for the synthesis of pyrimidines.
they are essential for the synthesis of purines.
they are essential for nitrogen metabolism.
our bodies need them for protein synthesis.
our bodies cannot synthesize them and therefore they need to be present in our diet.
Which amino acid does not have a primary α-amino group?
glutamine
arginine
lysine
proline
glutamate
Zwitterions are
amino acids.
ionic molecules that are racemic.
ions that bear both negatively and positively charged groups.
side chain carboxylate anions.
delocalized ions.
Which of the following amino acids has a charged polar side chain at pH 7.0?
Leu
Ala
Met
Trp
Glu
Which of the following amino acids has a sulfur atom in its side chain?
Asn
Ser
Phe
Met
Tyr
The disulfide bond between two cysteine molecules
is a peptide bond.
is an ionic interaction that is stable at physiological pH.
is a covalent bond formed by oxidation.
is a hydrogen bond between the two sulfhydryl groups.
is a dipole-dipole interaction.
The isoelectronic point of an amino acid is the point where
the pKa of the α-carboxylic acid is the same as the pKa of the α-amino group.
the α-carboxylic acid is protonated and the α-amino group is unprotonated.
the solubility of the amino acid is maximized.
the α-carboxylic acid and the α-amino group are both half protonated.
the amino acid carries no net electrical charge.
The peptide AYDG has an N-terminal _________ residue.
glycine
glutamic acid
glutamine
aspartic acid
alanine
Ribosomes use L amino acids to synthesize proteins. These amino acids are called “L” because
they are chiral.
they turn polarized light to the left.
they have a configuration of groups around the Cα that can be related to the configuration of groups around the asymmetric carbon in L-glyceraldehyde.
they are all (S)-amino acids.
they are all (R)-amino acids.
Typically, modified amino acids, those with side chain modifications that are present in proteins,
are synthesized due to genetic mutations.
are assembled by specialized bacterial enzymes.
are formed by modification of standard side chain residues after the protein is synthesized.
are toxic.
are racemic.
Which of the following has the most dramatic influence on the characteristics of an individual protein?
the amino-acid sequence
the amino-acid composition
the location of its encoding gene within the genome
the stereochemistry at the a-carbon
the sequence of tRNA molecules involved in its translation
Which physical characteristic is not commonly used in protein separation?
solubility
stereochemistry
size
charge
polarity
Adding additional salt to a protein solution can cause:
an increase in solubility called ‘salting in’.
a decrease in solubility called ‘salting out’.
protein precipitation from solution.
all of the above
none of the above
You are trying to separate five proteins, which are listed below, by gel filtration chromatography. Which of the proteins will elute first from the column?
cytochrome c (12 kDa)
RNA polymerase (99 kDa)
glutamine synthetase (621 kDa)
interferon-γ (34 kDa)
hemoglobin (62 kDa)
SDS-PAGE separates proteins primarily due to differences in
isoelectric point.
mass.
polarity.
solubility.
amino acid sequence.
In two homologous proteins, which residue is most likely to replace a Glu residue as a conservative substitution?
Asp
Trp
Met
Ile
Lys
In a protein, the most conformationally restricted amino acid is ______; the least conformationally restricted is ______.
Trp, Gly
Met, Cys
Pro, Gly
Ile, Ala
Ala, Pro
Which one of these characteristics is not true for the α helix?
There are 3.6 amino acids per turn.
There is a requirement for glycine every third amino acid residue.
A hydrogen bond forms between the carbonyl oxygen of the nth amino acid residue and the -NH group of the (n + 4)th amino acid residue.
Proline is typically not found in the α helix.
It is right-handed.
Which of these characteristics does not describe the β sheet?
Amino acid side chains are located both above and below the sheet.
β sheets have a pleated edge-on appearance.
They can exist in either parallel or antiparallel configurations.
The sheets contain as few as two and as many as 22 polypeptide chains.
Parallel β sheets containing fewer than five chains are the most common.
Which of the following amino acids combinations have side chains with groups that have the greatest ability to stabilize the tertiary structure of a protein?
Lys and Arg
Cys and Glu
Glu and Lys
Gln and Glu
Pro and Asp
Which of the following occurs first when folding a disordered polypeptide chain into a stable protein formation?
formation of a low energy state
association of ordered subunits
aggregation of hydrophobic regions in the protein
tertiary structure refinement
formation of a low entropy state
In general molecular chaperone proteins function by
mediating disulfide bond formation.
synthesizing new proteins when one is misfolded.
preventing premature folding by binding hydrophobic regions of the protein.
enhancing salt bridge formation.
none of the above
Proteins can denature due to a change in
pH
temperature
ionic strength
all of the above
none of the above
Which structure shown in the figure above is a ketohexose?
A
B
C
D
none of the above
Alcohols react with aldehydes to form
hemiketals.
lactones.
lactams.
glycosides.
hemiacetals.
A saccharide that has free aldehyde group is called a(n) _____________.
ketose
nonreducing sugar
reducing sugar
aldohexose
alditol
Which of these polysaccharides is a branched polymer?
chitin
amylose
cellulose
amylopectin
hyaluronic acid
Glycoproteins
are only found in bacteria.
are extremely homogeneous.
are typically less than 1% carbohydrate by weight.
are assembled under strict genetic control.
exhibit microheterogeneity.
N-linked oligosaccharides can be covalently linked to proteins at which amino acid?
Gly
Ser
Glu
Tyr
Asn
Which of the following lipid types is the least polar?
triacylglycerols
glycerophospholipids
sphingolipids
gangliosides
glycolipids
Cholesterol
incorporation into the membrane results in increased rigidity.
functions as a precursor to cerebrosides.
is synthesized in two-carbon units.
is synthesized from steroid hormones.
all of the above
Unsaturated fatty acids:
are commonly found in plants and animals
usually contain a double bond with cis stereochemistry
sometimes contain multiple double bonds
have lower melting points than the analogous saturated fatty acids
all of the above
Which of the following is comprised primarily of fatty acids and other single tailed amphiphiles?
lipid bilayers
two-dimensional membranes
liposomes
micelles
solvent-filled vesicles
The _________ model describes the cell membrane as an assortment of integral proteins suspended freely in a lipid bilayer.
FRAP
cellular fusion
transverse diffusion
lateral diffusion
fluid mosaic
Glycosphingolipids with several attached carbohydrates (including at least one sialic acid) are called:
plasmalogens
ceramides
sphingosides
gangliosides
cerebrosides
Which of the structures above is an example of an ω-3 polyunsaturated fatty acid?
A
B
C
D
none of the above
Coated vesicles are used to ensure that the enclosed protein maintains its proper orientation. Clathrin is one type of protein used to coat vesicles. Which of the following is true regarding clathrin vesicles?
They transport proteins between successive components of the Golgi compartments.
They transport transmembrane proteins and GPI-linked proteins from the Golgi to the plasma membrane.
They transport proteins from the ER to the Golgi.
They form a rigid complex capable of protecting protein structure and orientation as it is passed from hydrophobic to hydrophilic environments.
None of the above.
A pore that simultaneously transports two different molecules in different directions is called
a symport.
a uniport.
a gap junction.
an equilibrium channel.
an antiport.
Based on the diagram above, which of the following statements is TRUE?
F requires ATP directly
B is an example of symport
B is gradient driven
B requires ATP directly
none of the above are true
Which of these amino acid groups would not make a good nucleophilic catalyst?
amino
sulfhydryl
imidazole
methyl
hydroxyl
Which of the following is TRUE about enzymes?
I. Enzymes typically catalyze reactions at much higher rates than chemical catalyst.
II. Enzymes are often very specific for their substrates.
III. Enzyme activities can often be regulated.
IV. Enzymes typically act under milder conditions of temperature and pH than chemical catalysts.
I, II, III
I, II, III, IV
II, II
III, IV
II, III, IV
Proton transfer from an acid, lowering the free energy of a reaction’s transition state, is characteristic of
electrostatic catalysis.
nucleophilic catalysis.
general base catalysis.
general acid catalysis.
concerted acid-base catalysis.
Which of the following processes would yield and increase in rate?
the proximity of the reacting groups
the rotational motions of the substrates and catalytic groups
the orientations of the substrates and catalytic groups
all of the above
none of the above
The transition state of an enzyme and substrate reaction
must always bind the enzyme active site with lower energy than the products.
is stabilized by enhancing the reverse reaction of E + S→ES.
is composed of true covalent bonds which decrease its energy.
is stabilized due to the specificity of the active site for the substrate.
is stabilized by decreasing the effective concentration.
Research scientists are trying to clone a gene. In order to accomplish this task they join two pieces of DNA. Which class of the enzymes below might accomplish this task?
oxidoreductase
ligase
hydrolase
isomerase
lyase
The enzyme pictured above is shown in two configurations, A (open) and B (closed). Upon binding substrate in the active site, the enzyme converts the structure shown in B. Which of the following is true based on the given information?
The enzyme requires a high concentration of substrate to function.
This example exemplifies the “lock-and-key” model.
This enzyme must require ATP.
This example exemplifies the of “induced fit” model.
None of these are true.
For a reaction A + B → C, if the concentration of B is much larger than A so that [B] remains constant during the reaction while [A] is varied, the kinetics will be
sigmoidal.
pseudo-first-order.
unimolecular.
zero-order.
hyperbolic.
KM is
a measure of the catalytic efficiency of the enzyme.
equal to half of Vmax.
the rate constant for the reaction ES → E + P.
the [S] that half-saturates the enzyme.
a ratio of substrate concentration relative to catalytic power.
An enzyme is near maximum efficiency when
its turnover number is near Vmax.
kcat/KM is near 108 M-1s-1.
k1 << k-1.
kcat/KM is equal to kcat.
KM is large when k2 exceeds k1.
A compound that distorts the active site, rendering the enzyme catalytically inactive is called
a uncompetitive inhibitor.
an allosteric effector.
an inactivator.
a competitive inhibitor.
none of the above
Allosteric activators
bind via covalent attachment.
stabilize conformations with higher Ks.
stabilize conformations with higher substrate affinity.
all of the above
none of the above
From the graph above plotting data that was collected under steady state conditions, velocity on the y-axis in units of μM/s and substrate concentration of the x-axis in units of μM, what is the KM?
0.24 μM/s
18 μM
0.2 μM
0.24 μM
0.12 μM/s
