Biochem Final
Which of the following statements are true?
ATCase is regulated by feedback inhibition.
Which of the following is not an important metal in biological systems?
Al3+
Calculate the net delta G for the following series of reactions:
-6 kJ/mol IMAGE
What is the pI of the dipeptide shown? (Use the pK as given.)
5 IMAGE
hich represents the correct arrangement of bonding in a peptide bond?
C-C=O-NH-C IMAGE
Which of the following is the correct formula for glucose?
C6H12O6
In the figure below, K M is indicated at
D IMAGE
What is the peptide sequence Asp-Gln-Gly-Ser, using one-letter abbreviations for the amino acids?
DQGS
Consider the following interaction between a protein and its ligand: [P] + [L] --> [PL]. Which equation describes the dissociation constant of this interaction?
[P][L] / [PL]
The peptide bond
has a mix of single and double bond characters.
When ATP binds to myosin,
it cannot interact with actin.
Osmosis is
movement of water across a membrane
Below are five biological reactions. Which one is most likely to proceed in the direction as written?
C— B->E delta G=-12kj/mol IMAGE
Place the following steps of the apoptotic pathway in their proper order. A. CASP3 cleavage of cellular proteins B. Cleavage of procaspase 8 C. Cleavage of procaspase 3 D. Assembly of DD and DED protein complexes
D, B, C, A
The stop codons in mRNA are UAA, UAG and UGA. Considering only the 3rd position of the codon, how many other codons are subject to sustaining a nonsense mutation that would lead to the production of one of these? Choose the ONE based answer.
4 IMAGE
Which of the following is true of the tetrahedral intermediate in the chymotrypsin mechanism?
It contains an oxyanion.
What does glycolysis accomplish for the cell?
It generates ATP and pyruvate for the cell to be used in other cycles.
Which enzyme is the main regulator of glycolysis?
PFK-1
Which of the following is activated or increased in a liver cell on exposure to either glucagon or epinephrine?
cAMP
The mechanism of HMG-CoA reductase involves
two NADPH.
Below is a Lineweaver-Burk plot in which the axis labels have been removed. Interpret the plot to determine the Km.
0.33 IMAGE
Great Salt Lake in Salt Lake City, UT has a pH of 10.2. What is the [OH-] in the lake?
1.58 x 10-4 M
Consider a weak acid whose pKa is 6.45. What is the ratio of conjugate base to conjugate acid needed to make a solution that is pH 7.5?
11.2
As 18 Na + ions are exported out of the cell by the Na +-K + ATPase membrane transport protein, __________ K + ions are imported into the cell.
12
Which reactions in the citrate cycle produce CO 2?
3 and 4 IMAGE
Using the figure below describing monoclonal antibody generation, identify the step where the B cells are fused with the tumor cells.
4 IMAGE
Below are the steps of solid-phase peptide synthesis:1. The protecting groups of the amino acids are removed. 2. The peptide is released from the solid support resin. 3. An incoming amino acid is activated at the carboxyl group by DCC and added to the column. 4. Fmoc is removed by treatment with a base and the C-terminal amino acid is attached to the resin molecule. 5. The resin bound C-terminal amino acid and the incoming N-terminal amino acid are coupled. What is the appropriate order of these steps?
4, 3, 5, 1, 2
If the Ka of an acid is 1.50 x 10 -7, what is the pKa?
6.82
Using the oxygen binding curve shown, calculate the approximate percentage of O 2 that is released from hemoglobin as the pO 2 changes from 13 kPa to 4 kPa.
60%
Which of the following peptides would be eluted last when separated using gel filtration chromatography?
A IMAGE
You learned about the importance of hydrophobic interactions in Chapter 2. Considering this, which of the following might you consider to be TRUE statements about their importance? They guide the 3-D folding of a polypeptide. They are important for the spontaneous formation of membranes. They guide enzyme-substrate interactions. They guide interactions between receptors and ligands.
All of these answers are correct.
The catalytic triad of chymotrypsin is composed of His57, Ser195, and
Asp102.
Construct a functional pathway out of the following steps. A: Phosphorylation of mc042-1.jpg subunits of the insulin receptor occurs. B: Insulin binds to mc042-2.jpg subunits of the insulin receptor. C: PI-3K is activated. D: IRS is phosphorylated.
B, A, D, C
Refer to the reaction coordinate diagram below. The change in the activation energy of the reaction because of the presence of an enzyme is illustrated by the energy of __________ minus the energy of __________.
B,C IMAGE
Place the following steps in proper order:A. phosphorylation of RTK cytoplasmic tails B. activation of downstream signaling pathways C. ligand binding, receptor dimerization, and kinase activation D. protein binding to RTK phosphotyrosines and phosphorylation of target proteins
C, A, D, B
Below is a schematic representation of a dimerized receptor tyrosine kinase. Where is the kinase function located?
D. IMAGE
Ovaries produce estrogen. A Western blot analysis of the expression of estrogen receptors in ovarian tissues at different times of the estrous cycle showed approximately four times greater protein levels at day 2 compared with day 10 of the cycle. Which of the following may be true given these data?
Estrogen is acting as an autocrine signal in the ovaries.
Which of the following are negatively charged amino acids at pH = 7?
Glu, Asp
Which of the following macromolecules would yield only one type of monomer after complete hydrolysis?
Glycogen
If protein kinase A is activated in a liver cell in response to glucagon binding to the B2-adrenergic receptor, which of the following will result?
Glycogen degradation will be turned on.
Levels of diacylglycerol increase in a cell on binding of a ligand to a taste receptor. Which trimeric G protein subunit is most likely to be bound to GTP?
Gqa
List the 10 enzymes required for glycolysis
Hexokinase, phosphoglucoisomerase, phosphofructokinase-1, aldolase, triose phosphate isomerase, glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase, phosphoglycerate mutase, enolase, and pyruvate kinase.
Write the full name of this amino acid in the space below:
Histidine IMAGE
What are the chemical bonds that stabilize the alpha helix called?
Hydrogen
Which of the following is true of the induced-fit model of enzyme catalysis but NOT of the lock and key model of enzyme catalysis?
It involves a conformational change of the enzyme.
A cell with a membrane potential of −70 mV that contains functioning Na +-K + ATPase membrane transport proteins will maintain an extracellular __________ concentration that is __________ than the intracellular __________ concentration.
K+; lower; K+
In a reversible covalent modification reaction involving the phosphorylation of a target protein, which of the following amino acids is LEAST likely to be modified with a phosphate group?
Phe
Which of the following statements is true of the data shown below?
Protein B and protein A bind to the same ligand. IMAGE
On insulin binding to the insulin receptor, MAP kinase signaling proteins are activated. Which of the following proteins are part of this signaling pathway?
Shc
The sarcomere length of isolated heart myoblasts can be measured over time in the laboratory. The myoblasts are maintained in a buffer during the experiment. In a control experiment, Ca 2+ and ATP are added to the buffer and the change in sarcomere length is analyzed. If EDTA, a chelating agent that sequesters Ca 2+, was included in the buffer, the length change would be __________ compared with a control experiment without EDTA.
Smaller
Which gives rise to a favorable enthalpic (delta S) driving force for protein folding?
The decrease in ordered water molecules as hydrophobic amino acids pack together.
Which of the following do you think most influences the lower limit of van der Waal's radii?
The electron clouds begin to repel each other.
If energy in the form of ATP is required to make a polymeric macromolecule, which of the following will happen if there is no ATP available?
The polymer is broken down to release ATP. IMAGE
Which scenario would allow mc029-1.jpg-arrestin to bind to the GPCR?
The receptor is phosphorylated.
What are the three-letter and one-letter abbreviations for the amino acid tyrosine?
Tyr, Y
Rank the following in terms of INCREASING order (weakest is first to strongest as fourth):
Van der waals interaction Hydrogen bond Ionic bond Covalent bond
A ligand binds to a transmembrane protein. This causes a conformational change in the protein that is detected by an intracellular protein. The intracellular protein is an enzyme that adds phosphate groups to target proteins. The phosphorylated proteins cause a physiological change within the cell. This is an example of
a signal transduction pathway.
Which enzyme of the citrate cycle catalyzes the oxidative decarboxylation reaction that produces CO 2, NADH, and succinyl-CoA?
a-ketoglutarate dehydrogenase
In the following figure, what is the linkage between the two monosaccharide units and is this a reducing sugar?
a1->B2,nonreducing IMAGE
The primary function of the citrate cycle is to oxidize
acetyl-CoA.
When bound to GTP, Gsa obtains a conformation that promotes interaction with
adenylate cyclase.
Write the full name of this amino acid in the space below:
arginine IMAGE
Consider a mutation in procaspase 3 that changes Asp28 to an amino acid that is no longer a substrate for autocleavage. This mutant would
be partially activated.
If the concentration of aspartate in the cell decreased, what would be the predicted outcome?
decreased concentration of fumarate
If a metabolic enzyme __________ the energy of activation of a reaction, the rate of product formation will __________.
decreases; increase
Which of the following best defines substrate-level phosphorylation?
direct transfer of a Pi to an ADP
Which stabilizing force in protein tertiary structures is a covalent bonding force?
disulfide bonding
Fructose-1,6-bisphosphate is cleaved by aldolase. What is required for the reaction to proceed?
formation of Schiff base intermediate
Which of the following metabolic conversions is considered to be the major control point of glycolysis?
fructose-6-phosphate —>fructose-1,6-bisphosphate
Which reaction in glycolysis is a redox reaction?
glyceraldehyde-3-P —>1,3-bisphosphoglycerate
Which of the following proteins contains an SH3 domain?
growth factor receptor-bound 2 (GRB2)
All of the following are stabilizing forces in maintaining a stable protein tertiary (3 mc037-1.jpg) structure, EXCEPT
high temperature
Vitamin C is required for prolyl hydroxylase to function. Prolyl hydroxylase enzyme activity is necessary for the proper biosynthesis of collagen. Which of the following might result from a deficiency in vitamin C?
higher risk of bone breakage
If an enzyme carries out acid-base catalysis, which of the following amino acids could act as general acid?
histidine
Protein secondary structures such as a-helices and B-sheets are stabilized mainly by
hydrogen bond formation.
A molecule is found to be able to diffuse across a membrane. Which of the following characteristics would best describe this molecule
hydrophobic
The three general categories of enzyme-mediated reactions, which are determined on the basis of the work they accomplish, include all EXCEPT
hydrophobic collapse reactions.
Acetylcholinesterase is an important enzyme in the nervous system. Acetylcholinesterase activity is blocked by the nerve agent sarin gas, which forms a covalent bond with a Ser in the active site of the enzyme. Sarin gas is a(n)
irreversible inhibitor.
A Lineweaver-Burk plot displays parallel lines for an enzyme in the absence and presence of increasing amounts of an inhibitor. The inhibitor in this experiment
is uncompetitive.
According to the delta G', which of the following exergonic reactions is most likely irreversible under normal cellular conditions and is considered to be the rate-limiting step of the citrate cycle?
isocitrate dehydrogenase
Where do citrate cycle reactions in eukaryotic cells take place?
mitochondrial matrix
A double helix that crosses itself in a right-handed twist is referred to as a
negative supercoil
Which of the following is a way that an enzyme can increase the rate of a reaction inside a cell?
orienting substrates appropriately for the reaction to occur
Classify the reaction that occurs at step 4 in the reaction schematic of the pyruvate dehydrogenase reaction below.
oxidation reduction IMAGE
What type of transport is depicted in the figure below?
passive transport of molecules down a concentration gradient IMAGE
The first reaction in glycolysis that produces a high-energy compound is catalyzed by
phosphofructokinase-1
Which class of protein structures does the protein shown below fit into?
predominantly B-sheet IMAGE
What is the potential metabolic fate of pyruvate during strenuous exercise?
produce lactate
Cyclic pathways contain several metabolites that regenerate during each turn of the cycle. Another way to describe a metabolite is that it functions as a
reactant or product
A genetic analysis of an unknown infectious agent reveals that it contains only the nucleotides G, A, U and C in the proportion 30 percent, 35 percent, 15 percent and 20 percent respectively. Based on this information, this infectious agent is most likely a
single-stranded RNA virus
Muscle relaxation in response to nitric oxide would be reduced if a(n) __________ was present.
stimulator of cGMP phosphodiesterase
A shared intermediate can be defined as a molecule that is
the final product of a pathway and the reactant of the next pathway.
A requirement for a covalent bond to form between two atoms is that
there are unpaired electrons on each atom.
Regeneration of NAD + and FAD inside the mitochondrial matrix is required because
they maintain flux through the citrate cycle.
Consider an oxygen binding curve for hemoglobin at pH 7.4. The binding curve would shift __________ if the pH is reduced to 7.2.
to the right
Ligand binding causes which of the following to form trimers?
tumor necrosis factor receptors
Both the substrate and the tetrahedral intermediate, when associated with chymotrypsin,
undergo a nucleophilic attack.
The amino acid with the most hydrophobic side chain is
valine
The specific sites on the antibody that interacts with the antigen are
variable-domain amino acid residues.
Which of the following has the greatest entropy?
water vapor
