Exam 1 Flashcards by Angelise Hicks

When this polypeptide is treated with 1-fluoro-2,4-dinitrobenzene followed by hydrolysis the product
found is
A. dinitrophenyl-phenylalanine
B. dinitrophenyl-alanine
C. dinitrophenyl-alanine and d-dinitrophenyl-arginine
D. dinitrophenyl-alanine and dinitrophenyl-leucine
E. dinitrophenyl-phenylalanine and dinitrophenylalanine

B. dinitrophenyl-alanine

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When this polypeptide is treated with Carboxypeptidase A the first product found is
A. phenylalanine
B. alanine
C. arginine
D. leucine
E. dinitrophenyl-phenylalanine and d-dinitrophenyl-arginine

A. phenylalanine

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One of the amino acids in the polypeptide is Tryptophan the one letter abbreviation and structure of Tryptophan is
A. W, 1
B. T, 2
C. Y, 5
D. F, 3
E. W, 5

E. W, 5

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This polypeptide has ________ peptide bonds
Ala-Leu-Ser-Arg-Met-Val-Ile-Trp-Ala-Met-Ala-Ala-Phe
A. 8
B. 9
C. 11
D. 12
E. 13

D. 12

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When this peptide is subject to Edman degradation the 4 amino acids will be released in the following
order
A. F, A, A, M
B. A, L, S, R
C. A, F, S, R
D. A, F, S, A
E. L, S, R, M

B. A, L, S, R

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When this polypeptide is treated with cyanogen bromide the fragments formed will be
Ala-Leu-Ser-Arg-Met-Val-Ile-Trp-Ala-Met-Ala-Ala-Phe
A. Ala-Leu-Ser-Arg and Met-Val-Ile-Trp-Ala-Met-Ala-Ala-Phe
B. Ala-Leu-Ser-Arg-Met and Val-Ile-Trp-Ala-Met-Ala-Ala-Phe
C. Ala-Leu-Ser-Arg-Met and Val-Ile-Trp-Ala-Met and Ala-Ala-Phe
D. Ala-Leu-Ser-Arg and Met-Val-Ile-Trp-Ala and Met-Ala-Ala-Phe
E. all of the above

C. Ala-Leu-Ser-Arg-Met and Val-Ile-Trp-Ala-Met and Ala-Ala-Phe

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Cleavage of this polypeptide with chymotrypsin and trypsin will yield \_\_\_\_\_ and \_\_\_\_ fragments, respectively Ala-Leu-Ser-Arg-Met-Val-Ile-Trp-Ala-Met-Ala-Ala-Phe
A. 1 and 1
B. 3 and 3
C. 2 and 3
D. 2 and 2
E. 3 and 2

D. 2 and 2

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When this polypeptide is titrated one would expect that the titration curve would look like
Ala-Leu-Ser-Arg-Met-Val-Ile-Trp-Ala-Met-Ala-Ala-Phe

A. 1
B. 2
C. 3
D. 4
E. None of the above

D. 4

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Estimate the pI of the polypeptide.
 Ala-Leu-Ser-Arg-Met-Val-Ile-Trp-Ala-Met-Ala-Ala-Phe
A. 4.3
B. 6.0
C. 10.5
D. 2.2
E. 3.25

C. 10.5

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The overall tertiary structures of myoglobin and the a and b chains of hemoglobin are very similar. However, there are several regions on the myoglobin surface where the residues are polar or charged whereas these same regions on the surface of the a and b chains are nonpolar. The consequence of this change is that
A. There is no functional consequence to this change.
B. The chains of Hb stay apart in solution whereas those of Mb aggregate
C. The a and b chains of Hb associate into a tetramer due to hydrophobic interactions
D. The a and b chains of Hb associate into a tetramer due to polar interactions
E. The a and b chains of Hb associate into a tetramer due to the formation of salt bridges

C. The a and b chains of Hb associate into a tetramer due to hydrophobic interactions

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Answer the following two questions (11-12) based on the figures below
11. Structures A, B and C are mostly _____________, ____________, and ________, respectively
A. a-helical, b-sheet, and a + b
B. a-helical, b-sheet, and disordered
C. b-sheet, a-helical, and a + b
D. b-sheet, a-helical, and disordered
E. b-sheet, a-helical, and a + b + disordered

E. b-sheet, a-helical, and a + b + disordered

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. Using the Ramachandran plot below. Structure A above would likely have dihedral angles of
A. j = -60, Y = -60
B. j = -150, Y = +150
C. j = -60, Y = -150
D. j = --60, Y = +150
E. j = +60, Y = +60

B. j = -150, Y = +150

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Collagen and silk both are _____________ but differ in that the H-bonds in silk are ______ to the chain whereas those in collagen are ______________to (in) the collagen helix.
A. globular proteins, parallel, perpendicular
B. fibrous proteins, perpendicular, parallel
C. fibrous proteins, perpendicular, not involved
D. globular proteins, perpendicular, not involved
E. fibrous proteins, parallel, perpendicular

C. fibrous proteins, perpendicular, not involved

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Collagen has high percentages of hydroxyproline. This is not one of the 20(21) amino acids in the genetic code. Rather it is formed __________________ and this process requires _________, a lack of which results in ____________.
A. by posttranslational modification; vitamin D3; rickets
B. in the mitochondria; vitamin B; anemia
C. by post translational modification; vitamin C; sickle cell disease
D. by post translational modification; vitamin C; scurvy
E. by post translational modification; vitamin D3; scurvy

D. by post translational modification; vitamin C; scurvy

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Hemoglobin A and Hemoglobin S differ in that a __________residue on the ______ chain is replaced by
_______. This results in a(n) ___________ in the pI of the hemoglobin.
A. Glu; b; Val; increase.
B. Glu; a; Val; increase.
C. Glu; b; Leu; decrease.
D. Glu; b; Val; decrease.
E. Glu; a; Val; decrease

A. Glu; b; Val; increase.

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Sickle cell trait is highly associated with residence in certain parts of Africa and is related to increased resistance to \_\_\_\_\_\_\_\_\_\_\_\_\_\_. The linkage between these traits is called\_\_\_\_\_\_\_\_\_.
A. Beriberi; transduction.
B. Malaria; balanced polymorphism.
C. Malaria; gene hopping.
D. Beriberi; balanced polymorphism.
E. Malaria; transduction.

B. Malaria; balanced polymorphism

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Based on this graph
A. Mb binds O2 with higher affinity than Hb.
B. Hb binds O2 with higher affinity than Mb.
C. Hb binds O2 with higher affinity than Mb but only at pH 6.8.
D. Mb and Hb have the same affinity.
E. You cannot determine relative affinity from this graph.

A. Mb binds O2 with higher affinity than Hb

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The effect of pH shown in this plot is known as
A. Hill effect
B. Michaelis effect
C. Bohr effect
D. Menten effect
E. Lineweaver Burk effect

C. Bohr effect

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Assuming that the above graph was determined in the absence of BPG, the addition of BPG
would______________
A. Shift all curves to the right.
B. Shift all curves to the left.
C. Shift the curve for Mb to the right and the curves for Hb to the left.
D. Shift the curves for Hb to the right.
E. Shift the curves for Hb to the right and the curve for Mb to the left

D. Shift the curves for Hb to the right.

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CO (carbon monoxide) and CO2 both bind to Hb. However, CO is extremely toxic. One of the reasons is that
it has a much higher affinity than oxygen. 50% of the Hb subunits bound to CO is lethal. This is because
A. CO decreases the affinity of O2 for the remaining Hb subunits.
B. CO increases the affinity of O2 for the remaining Hb subunits.
C. CO and O2 do not bind at the same binding site.
D. CO has a lower Molecular weight than O2.
E. None of the above.

B. CO increases the affinity of O2 for the remaining Hb subunits

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Calculate the pH of a dilute solution that contains a molar ratio of potassium acetate to acetic acid (pKa =
4.76) of 5:1.

Answer formula: pH=4.76 + log(5/1)=5.46

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If bacterial cells are taken from an isotonic medium and placed in a hypotonic medium
A. They swell.
B. They shrink.
C. They remain the same.
D. They burst.
E. The nucleus leaks out of the cell

A. They swell

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Which of the following is likely to form a b-turn structure
A. Ala-Pro-Gly-Met.
B. Lys-Val-Phe-Trp.
C. Ala-Ala-Met-Val.
D. Gly-Pro-Hyp.
E. None of these forms a b-turn.

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A. Ala-Pro-Gly-Met

At what substrate concentration would an enzyme with a kcat of 33.0 s−1 and a Km of 0.0065 M operate at one-tenth of its maximum rate

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7.2 * 10^-4

``` If the substrate concentration [S] = 10Km, kcat = 33.0 s−1 , and the enzyme concentration was [ET], Vo would equal A. 30 [ET] B. Km C. 3.0 [ET] D. Km/Vmax E. None of the above ```

A. 30 [ET]

``` Which of the following is most likely to form an a-helix? A. Lys-Lys-Lys-Lys-Lys at pH 12 B. Lys-Lys-Lys-Lys-Lys at pH 7 C. Gly-Gly-Gly-Gly-Gly at pH 7 D. Glu-Glu-Glu-Glu-Glu at pH 7 E. Glu-Glu-Glu-Glu-Glu at pH 12 ```

A. Lys-Lys-Lys-Lys-Lys at pH 12

``` Which of the following sequences is most likely to form an a-helix at pH 7? A. Ala-Arg-Ala-Ala-Ala-Arg-Ala-Ala B. Pro-Pro-Pro-Pro-Pro-Pro-Pro C. Ala-Arg-Ala-Ala-Ala-Tyr-Ala-Ala D. Ala-Gly-Ala-Ala-Ala-Gly-Ala-Ala E. None of the above ```

C. Ala-Arg-Ala-Ala-Ala-Tyr-Ala-Ala

``` The horns of a rhinoceros, the wool of a sheep and the nails of our body are all composed of A. a-keratin B. silk C. collagen D. hemoglobin E. myosin ```

A. a-keratin

``` What is the functional group indicated by the letter B? A. carbonyl (ketone) B. hydroxyl group (alcohol) C. amino group (amine) D. carboxyl group ```

C. amino group (amine)

Covalent bonds place constraints on the shapes of biological molecules. As the size and complexity of a biomolecule increases, the conformational focus shifts from covalent bonds to noncovalent interactions. Noncovalent interactions dictate the stable, native conformations of large macromolecules and polymers while permitting the flexibility necessary for their biological functions. Which characteristics of weak noncovalent interaction enable the assembly, stability, and function of biomolecules? A. They are transient, whereas covalent bonds tend to be long-lasting. B. They have a large aggregate strength when multiple interactions are present. C. They are stable, requiring a large amount of energy to break. D. They do not interact with water in the environment.

A. They are transient, whereas covalent bonds tend to be long-lasting. B. They have a large aggregate strength when multiple interactions are present.

``` Size exclusion chromatography is a type of column chromatography that separates molecules by: A. size B. charge C. protein-ligand binding D. it does not separate molecules ```

A. size

A sample 0.762 g of an oligomeric protein of �r 157,250 was treated with an excess of 1-fluoro-2,4-dinitrobenzene (Sanger's reagent) under slightly alkaline conditions until the chemical reaction was complete. The peptide bonds of the protein were then completely hydrolyzed by heating it with concentrated HCl. The hydrolysate was found to contain 0.00259 g of DNP-Val. 2,4-Dinitrophenyl derivatives of the α-amino groups of other amino acids could not be found. Calculate the number of polypeptide chains in this protein. Give the answer as a whole number. How many polypeptide chains are in this oligomeric protein?

2 Polypeptide Chains

``` A diagram of cell fractionation is shown. What does the pellet contain at step C? A. Pellet contains nuclei and unbroken cells. B. Pellet contains mitochondria and peroxisomes. C. Pellet contains microsomes. D. Pellet contains ribosomes. ```

B. Pellet contains mitochondria | and peroxisomes

A claim put forth by some purveyors of health foods is that vitamins obtained from natural sources are more healthful than those obtained by chemical synthesis. For example, pure L-ascorbic acid (vitamin C) extracted from rose hips is thought to be healthier than pure L-ascorbic acid manufactured in a chemical plant. Select the true statement about synthetic vitamin C and vitamin C obtained from natural sources. A. Synthetic vitamin C that consists of pure L-ascorbic acid is equivalent to pure L-ascorbic acid that is obtained from natural sources. B. Impurities found in synthetic vitamin C pills won’t affect its bioavailability and toxicity. C. Synthetic vitamin C that consists of pure D-ascorbic acid is equivalent to pure vitamin C that is obtained from natural sources. D. The impurities found in synthetic vitamin C are the same impurities found in the vitamin C obtained from natural sources.

A. Synthetic vitamin C that consists of pure L-ascorbic acid is equivalent to pure L-ascorbic acid that is obtained from natural sources.

The concentration of acetylcholine (a neurotransmitter) in a sample can be determined from the pH changes that accompany its hydrolysis. When the sample is incubated with the enzyme acetylcholinesterase, acetylcholine is converted to choline and acetic acid, which dissociates to yield acetate and a hydrogen ion. In a typical analysis, 20. mL of an aqueous solution containing an unknown amount of acetylcholine had a pH of 7.16. When incubated with acetylcholinesterase, the pH of the solution decreased to 6.51. Assuming there was no buffer in the assay mixture, determine the number of moles of acetylcholine in the 20. mL sample

4.8 *10^-9

Holding one's breath can result in an increase in CO2(g) concentration in the blood. How would this affect the pH of the extracellular fluid? A. The pH decreases. B. The pH increases. C. The pH does not change appreciably. D. Cannot answer the question based on the information given

A. The pH decreases

``` Choose which is NOT a function of amino acids (free or in a bound form). A. neurotransmitters B. enzyme components C. metabolic intermediates D. hormones E. carriers of genetic information ```

E. carriers of genetic information

Which four statements about amino acids are true? A. Thr and Ser are polar amino acids. B. Threonine has more than one stereocenter (chiral center). C. The Val side chain does not form hydrogen bonds with other amino acids. D. Phe can undergo oxidation to form Tyr. E. Methionine is a thiol. F. The form of glycine used by the human body is D-glycine

A. Thr and Ser are polar amino acids. B. Threonine has more than one stereocenter (chiral center). C. The Val side chain does not form hydrogen bonds with other amino acids. D. Phe can undergo oxidation to form Tyr

``` Which protein or proteins have the highest pI value? A. a B. b and c C. d and e ```

C. d and e

A solution contains a mixture of three proteins, urease, serum albumin and lysozyme. The table gives the molecular weight, diffusion coefficient, and pI for the three proteins. Protein MW (Da) D (cm2/s) pI Urease 483,000 3.5 5.0 serum albumin 66,000 5.9 4.8 Lysozyme 14,400 11.2 11.0 40. Which protein will elute first on a gel filtration column? A. urease B. serum albumin C. lysozyme

A. urease

``` Choose the phrase that classifies a fibrous protein. A. some function as enzymes B. structure is rod-like C. structure is somewhat spherical D. hemoglobin E. soluble in water ```

B. structure is rod-like

Amyloid fibrils are associated with many fatal degenerative diseases of humans and livestock. Livestock diseases such as scrapie in sheep and bovine spongiform encephalitis (BSE, or mad cow disease) have major negative impacts on agriculture. Human diseases characterized by amyloid fibrils include Alzheimer's disease and Creutzfeldt-Jakob disease. The images show a short segment of a typical amyloid fibril. The image with the ball and stick structures shows the side chains protruding from the faces of the β-sheets. Choose the false statements about amyloid fibrils. A. Soluble proteins that misfold and form amyloid fibrils become insoluble. B. Amyloid fibrils have a high amount of β-sheet structure. C. Nucleation of amyloid structure may be triggered when two β-sheet regions from two partially folded proteins associate. D. An amyloid fibril is stabilized by hydrogen bonds between small hydrophilic residues

D. An amyloid fibril is stabilized by hydrogen bonds between small hydrophilic residues

The slope of the Hill plot is represented by nH and is also referred to as the Hill coefficient. Which sentence is true when nH is greater than 1? A. Oxygen binding is positively cooperative. B. Oxygen binding is noncooperative. C. Oxygen binding is negatively cooperative. D. Oxygen binding is uncooperative.

A. Oxygen binding is positively cooperative.

Select the true statements regarding antibody (specifically, immunoglobulin G) structure. A. The heavy and light chains are linked by noncovalent and disulfide bonds. B. Both the Fab and Fc fragments have variable domains. C. The antigen-binding site is formed as a combination of variable domains from one heavy and one light chain. D. The antigen-binding site is located in the Fc fragment. E. Both the Fab and Fc fragments contain constant domains.

A. The heavy and light chains are linked by noncovalent and disulfide bonds C. The antigen-binding site is formed as a combination of variable domains from one heavy and one light chain. E. Both the Fab and Fc fragments contain constant domains.

Which of the statements about enzymes are true? A. A substrate must bind to the active site before catalysis can occur. B. Generally, an enzyme is specific for a particular substrate. For example, thrombin catalyzes the hydrolysis of the peptide bond between Arg and Gly. C. An enzyme yields a specific product, whereas a nonbiological catalyst may produce more than one product with the occurrence of side reactions. D. Nonbiological catalysts and enzymes tend to have a similar degree of reaction specificity. E. Catalysis occurs at the active site, which usually consists of a crevice on the surface of the enzyme.

A. A substrate must bind to the active site before catalysis can occur. B. Generally, an enzyme is specific for a particular substrate. For example, thrombin catalyzes the hydrolysis of the peptide bond between Arg and Gly. C. An enzyme yields a specific product, whereas a nonbiological catalyst may produce more than one product with the occurrence of side reactions. E. Catalysis occurs at the active site, which usually consists of a crevice on the surface of the enzyme.

Consider the reaction. What effects are produced by an enzyme on the general reaction? A. The reaction equilibrium is shifted away from the products. B. The concentration of the products is decreased. C. ΔG for the reaction increases. D. The activation energy for the reaction is lowered.

D. The activation energy for the reaction is lowered.

Which condition occurs when the rate is directly proportional to [S]? A. [S]<>Km

A. [S]

Which condition occurs when the rate is half the maximum rate? A. [S]<>Km

B. [S]=Km

Answer the following questions (49-51) based on the scenario described below: For her undergraduate project, Jessica studied an enzyme that catalyzes the reaction A↽−−⇀B. For substrate A, she determined that Km=2.00 μM and kcat=40.0 min−1. Jessica graduated and her project has been passed on to you. Unfortunately, Jessica was so busy that she sometimes forgot to record all of the details of an assay in her lab notebook. Your mentor suggests that you try to back calculate some of the missing concentration values. Assume that the enzyme follows Michaelis–Menten kinetics. 49. In experiment A, where [A]=5.00 mM, she found that the initial velocity, V0, was 504 nM min−1. What was the [Et] in experiment A? A. 12.6 nM B. 16.3 nM C. 13.6 nM D. 16.2 nM

A. 12.6 nM

``` The compound Z was found to be a very strong competitive inhibitor of the enzyme, with an α of 10. In experiment C, in which the same [Et] was used as in experiment A but a different [A] was used, an amount of Z was added that reduced the rate 0 to 252 nM min−1. What was the [A] in experiment C? A. 10 µM B. 20 µM C. 20 mM D. 10 mM ```

B. 20 µM

``` A measure of the catalytic efficiency of an enzyme is the initial slope of the Michaelis–Menten curve at low [S], the second-order rate constant kcat/Km. A perfect enzyme, limited only by diffusion, would have a value of 108 or 109 M−1 s−1. Calculate kcat/Km for this enzyme. Has it reached perfection A. 3.33 x 10^5 M−1s−1, yes B. 3.33 x 10^5 M−1s−1, no C. 3.33 x 10^9 M−1s−1, no D. 3.33 x 10^-1 M−1s−1, no ```

B. 3.33 x 10^5 M−1s−1, no

The Lineweaver–Burk plot, which illustrates the reciprocal of the reaction rate (1/v) versus the reciprocal of the substrate concentration (1/[S]), is a graphical representation of enzyme kinetics. This plot is typically used to determine the maximum rate, Vmax, and the Michaelis constant, Km, which can be gleaned from the intercepts and slope. Identify each intercept and the slope in terms of the constants Vmax and Km. What term is represented by A? A. Km/Vmax B. 1/Vmax C. −1/Km

A. Km/Vmax

Which type of inhibitor is structurally similar to the substrate? A. Competitive inhibitor B. Uncompetitive inhibitor C. Mixed inhibitor

A. Competitive inhibitor

``` A plot of 1/V0 versus 1/[S], called a Lineweaver–Burk or double-reciprocal plot, is a useful tool for identifying the type of enzyme inhibition. What is type of inhibition indicated by the graph? A. Competitive inhibition B. Uncompetitive inhibition C. Noncompetitive inhibition D. The type of inhibition cannot be determined from the graph provided ```

A. Competitive inhibition

``` What kind of inhibitors are transition state analogs usually classified as? A. competitive inhibitors B. noncompetitive inhibitors C. uncompetitive inhibitors D. mixed inhibitors ```

A. competitive inhibitors

Exam 1 Flashcards

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