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Biochem 1/2
| Question | Answer |
|---|---|
| Covalent bonds example | disulfide bonds |
| Non-covalent interactions | hydrogen bonding, hydrophobic interactions, ionic bonding |
| Native protein: | a protein that is in its natural, functional form. The 3-D structure of a native protein is very important, as it allows the protein to most competently fulfill its biological function. |
| Denatured protein: | a protein that is in its denatured, non-functional form. The denaturation of a protein causes the protein to lose all of its structural features, such as its intra-chain and inter-chain disulfide bridges. |
| The verification of a protein’s full structure requires | X-ray diffraction analysis, which requires a homogeneous (pure) solution of the protein. |
| As with any protein, an enzyme’s activity strongly depends on | its native 3-D molecular structure. The activity of an enzyme is easy to monitor using a color reaction |
| Chaotropic Agents are small molecules that | perturb the 3-dimensional structures of macromolecules, such as proteins, when added at a high-enough concentration. These agents interfere with proteins’ internal non-covalent interactions, weakening both the polar and hydrophobic interactions |
| Reducing agents | are small molecules that reduce disulfide bridges, leaving the cysteine residues in proteins uncoupled |
| Most proteins will denature at temperatures above | 42o C. |
| Dialysis is the separation of smaller molecules from larger molecules using | semi-permeable, membrane and is made of a material (such as cellulose) that will allow small compounds, but not proteins, to diffuse in and out across the concentration gradient |
| Protein folding phase 1 | a relatively rapid folding of the protein chain into secondary structures, alpha helices and beta sheets. This protein structures further combine into super-structures mainly based on entropy |
| Protein folding phase 2 | folding the protein structures further to form a completely folded and more compact protein. Occurs slowly and is a random, trial-and-error process. |
| Protein folding ends with a protein that | is in the most stable, lowest-energy configuration |
| This trial-and-error process of finding the final configuration is sometimes, but not always, assisted by specific proteins, called | chaperone proteins. |
| The pentapeptide leucylglycylthreonyltyrosylalanine is first incubated with l-fluoro-2,4-dinitrobenzene (FDNB). When the resulting compound is heated to 110oC for 24 h in the presence of 6 M HCl, the solution will contain: | five alpha-amino acids with only leucine labeled by FDNB. |
| A protein has a mm of 200 kDa by gel filt. When separated by SDS-PAGE only one appeared with a mass of 100 kDa. When determined by SDS in combo with a red. agent (exactly 2 polypep. appeared of sz 40 and 60 kDa. What is the structure of nat. protein? | The native protein is made of two 40 kDA and two 60 kDA polypeptides |
| Dr. Strangelab performed peptide mapping to a polypeptide he had purified by using a protease. All the fragments had either arginine or lysine residues at their C terminal end except one that had glutamic acid. The protease Dr. Strangelab used was- | Trypsin |
| The graph depicts the elution profile from a positively-charged ion exchange resin. which of the proteins adhered more tightly to the resin? | 5 |
| The graph above depicts the elution profile from a positively-charged ion exchange resin. The peak labeled "X" consists of: | The amino acids that did not bind to the column |
| We have isolated an unknown human protein. By determining the amino acid sequence of a 15-25 residue-long portion of it we can- | Find the gene coding for the protein by searching the genebank database |
| The peptide alanylglutamylglycylalanylleucine has: | four peptide bonds. |
| The following compound is- (Cyclohexene-N=C=S) | PITC |
| The graph above depicts the elution profile of a hydrophobic column. The proteins eluting as "X" are- | The most hydrophilic |
| Electrophoresis in the presence of SDS separates proteins almost exclusively on the basis of: | Mass |
| Why is column chromatography performed at the end of every cycle of Edman degradation? | To determine the identity of a labeled amino acid |
| In a mixture of the five proteins listed below, which should elute LAST in size-exclusion (gel filtration) chromatography? | cytochrome c, Mr = 13,000 |
| We are using a fraction collector in column chromatography because- | Proteins that have separated in the column and elute at different time from the column are dispensed into different tubes and therefore they stay separated. |
| Molecules that differ in size can be separated from each other by which of the following methods- a. dialysis b. gel-filtration c. gel electrophoresis | A, B, and C |
| Free amino acids are larger than their residues in proteins by- | 18 daltons |
| In affinity chromatography, the bound proteins are typicallty eluted by a solution containing: | Ligand |
| The reagent used in the Edman degradation is- | PITC |
| Which of the following pentapeptides is expected to be the BEST dissolved in water? | NH2 ser tyr gly ser gln asp COOH |
| At any pH above the pI of the amino acid, the population of a given amino acid in solution will: | have a net negative charge. |
| In SDS-PAGE, the protein sample is typically treated with a reducing agent. This treatment allows- | To separate a multi-subunit protein to its individual polypeptides |
| Which method of protein chromatography can accomplish the greatest level of purification in a single step? | affinity chromatography |
| Proteases are useful in sequencing because- | Protease digestion allows reducing the size of a polypeptide so it is manageable for Edman degradation. |
| The flow-through fraction in ion exchange chromatography of amino acids in which a cation exchange resin was used is expected to contain mainly: | Negatively charged amino acids |
| The functional differences, as well as differences in three-dimensional structures, between two different enzymes from e. coli result directly from their different: | amino acid sequences. |
| During chromatography of proteins on a hydrophobic column: | Ammonium sulfate will increase the partitioning of proteins into the stationary phase. |
| To cleave a polypeptide next to a lysine residue, one can use which of the following enzymes- | trypsin |
| 4 proteins, each containing 1 polypeptide, are separated by SDS-PAGE: human cytochrome c (MW 13k), human serum albumin (MW 67k), bovine myoglobin (MW 16,890), and human apolipoprotein B (MW 513k). Which one would show up as the band at bottom of the gel? | cytochrome c |
| Which of the following interactions is NOT a basis for an affinity chromatography procedure? | Negative charge- positive charge |
| Which of the following is correct with respect to the amino acid composition of proteins? | Proteins with different functions usually differ significantly in their amino acid composition. |
| The formation of a peptide bond between two amino acids is an example of a(n) ______________ reaction. | condensation |
| Resonance | the state attributed to certain molecules of having a structure that cannot adequately be represented by a single structural formula but is a composite of two or more structures of higher energy. |
| In the cis configuration, the two alpha carbons | are oriented on the same side of the peptide bond. |
| In the trans configuration, the two alpha carbons | ) are oriented on opposite sides of the peptide bond. |
| Phi (Φ) | is the angle of rotation for the bond between the alpha carbon and the nitrogen atom. |
| Psi (Ψ) | is the angle of rotation for the bond between the alpha carbon and the carbonyl carbon. |
| X-ray crystallography is used to determine | the Phi and Psi. |
| Protein Conformation: | The 3-dimensional shape of the protein |
| Native Conformation: | Functional conformation of the protein found under normal biological conditions. |
| Primary Structure | - amino acid sequence of the polypeptide chain |
| Secondary Structure | - specific geometric shape caused by intramolecular and intermolecular hydrogen bonding of amide groups, mainly form alpha helixes and beta pleated sheaths |
| Motif | - segments of tertiary protein structure or amino acid sequence that are found in many proteins - A super-secondary structure- simple arrangements of secondary structures that frequently occur in protein structure |
| Domain | - element of protein structure, self-stabilizing and fold independently - Retain their structure even when separated from the rest of the protein |
| Tertiary Structure | - three-dimensional structure of a single protein molecule - A protein made up of several motif proteins. |
| Quaternary Structure | - formation of several protein molecules or polypeptide chains |
| Hydrophobic interactions contribute most to tertiary structure due to | an increase in entropy and greater free energy difference, resulting in significant stabilization. |
| Beta-pleated sheets consist of | beta strands that are connected by at least two or three hydrogen bonds. This forms a pleated sheet. |
| Regulatory Proteins | Regulate metabolic functions. Ex: Hormone-receptors, intra-cellular, signal transducers, protein kinases, transcription factors |
| Defensive Proteins | Protective function. Ex: Immunoglobulins, fibrinogen, thrombin |
| Structural Proteins | Support function, Collagen, elastin, keratin |
| Contractile Proteins | Can contract and change shap. Ex: Elements of cytoskeleton and muscle: myosin, actin |
| Storage Proteins | Ovalbumin, ferritin, casein |
| Enzymes | Catalytic activity. Ex: Catalase, synthase, dehydrogenase |
| Hemoglobin | is a multi-polypeptide protein that carries oxygen and CO2 in the circulatory system |
| Myoglobin | has a single polypeptide that is located primarily in muscle tissues; it “picks up” oxygen where hemoglobin has “dropped” it and carries it deeper into the tissues. |
| The structure beta-pleated sheets is maintained by- | Hydrogen bonding between the amide hydrogen in one side and the carbonyl oxygen on the other |
| Glycine is typically the only amino acid to be found in the "white" areas of a Ramachandran plot. This is because- | Glycine has a very small side-chain |
| The illustration below shows a peptide linkage between two residues. The individual atoms are numbered 1-10. Based on your knowledge of the properties of the peptide bond, which atoms are situated in the same geometric plane? | 3-8 |
| Which of the following pentapeptides is expected to be the LEAST dissolved in water? a. NH2-ser-tyr-gly-ser-gln-asp-COOH b. NH2-tyr-thr-gly-phe-gln-asp-COOH c. NH2-ser-ala-gly-phe-glu-asp-COOH d. NH2-gly-leu-phe-val-ser-gly-COOH | D |
| Which of the following is true? - Each peptide bond has double-bond chter due to reson. and cant rotate - 3 bonds separate sequential alpha carbons in polypeptide - The N--Cα bond in a polypeptide can rotate - The C—N bond in a bond cannot rotate | All of the above |
| The selective removal of chaotropic and reducing agents in Anfinsen's experiments was made by using which of the following techniques? | Dialysis |
| A motif in proteins is | a supersecondary structure that may be found in several different proteins |
| Which of the following is TRUE about proteins? | The folding process of proteins is hierarchical, with secondary structures forming before tertiary structures |
| The single most important contribution to the conformation of a protein in solution is the: | entropy increase from folding of the hydrophobic residues towards the inside of the protein. |
| Which of the following is correct with respect to the amino acid composition of proteins? | Proteins with different functions usually differ significantly in their amino acid composition. |
| Which of the following describes the overall three-dimensional folding of a polypeptide? | tertiary structure |
| How many residues are included in one turn of an alpha-helix structure? | 3.6 |
| The experimental procedure used to determine the precise arrangement of atoms within a large protein includes: | a. X-ray diffraction b. crystallogrpahy c. 3-D modelling tools d. working with Ramachandran plots |
| The C—N bond of a peptide is somewhat _______ than the C—N bond in a simple amine | Shorter |
| Urea is a molecule that | causes denaturation for proteins in solution |
| A domain in proteins is- | a distinct part of a protein that has its own independent structure and function |
| The peptide alanylglutamylglycylalanylleucine has: | four peptide bonds |
| In the diagram below, the plane drawn behind the peptide bond indicates the: | absence of rotation around the C - N bond because of its partial double-bond character. |
| We can be certain that a protein becomes a random coil when- | it is treated with a chaotropic and a reducing agent |
| The formation of a peptide bond between two amino acids is an example of a(n) ______________ reaction. | condensation |
| The Phi Φ and Psi ψ angles of one alpha carbon located in the center of an alpha helix in myoglobin are -60o and -45o, respectively. Which of the following statements is CORRECT? | b. The alpha carbon described above is expected to have very similar or identical Phi and Psi as its neighboring alpha carbons |
| Proline residues | . Are typically not found in alpha helices due to their conformational inflexibility |
| DTT is a chemical that- | releases a hydrogen atom that is taken up by other molecules |
| Which of the following groups correctly shows intrachain hydrogen bonding ||| in an alpha helix? | -C=O ||| H-N- |
| Which of the following refers to particularly stable arrangements of amino acid residues in a protein that give rise to recurring patterns? | secondary structure |
| The following compound is- (O=CNH2NH2) | a chaotropic agent |
| The major reason that antiparallel beta-stranded protein structures are more stable than parallel beta-stranded structures is that: | parallel ones have weaker hydrogen bonds between adjacent strands. |
| The functional differences, as well as differences in three-dimensional structures, between two different enzymes from e. coli result directly from their different: | amino acid sequences |
| A Ramachandran plot graphically displays- | The two angles of rotation around any number of alpha-carbon atoms in a protein |
| A protein's native 3D structure represents- | The lowest energy state of all possible conformations |
| BPG binds in the central cavity of | deoxyhemoglobin . Binds only to T- state. |
| BPG will affect the overall oxygen binding capacity in the tissues by | keeping more hemoglobin is in the T state. |
| Fetal Hb contains a gamma subunits that are replaced by | beta subunits after birth. |
| What determines the rates of chemical reactions? | Frequency of Collisions: Concentration of reactants , Temperature (increased rate of molecular diffusion) Energy of collisions. |
| Activation energy is the amount of energy that must be overcome in order for | a chemical reaction to take place. |
| The Transition State is | the high energy barrier for the reaction to proceed. It is always there, whether the reaction is Exergonic or Endergonic. |
| Lock and Key- | complementarity exists before interaction. (Enzyme pocket fits substrate). Reactants more stable. |
| Induced fit- | enzyme and substrate have weak initial attraction and change shape after binding for tighter grip (think of a hand shake). |
| Exo-peptidases: | Cleave the Peptide bonds non-specifically, in a progressive way, from polypeptide ends |
| Endo-peptidases: | cleave peptide bonds at specific locations along the polypeptide (in the middle) |
| A prosthetic group of a protein is a non-protein structure that is: | permanently associated with the protein |
| The interactions of ligands with proteins: | are usually short-lived |
| The following illustration shows: | That in the presence of E7, the binding configuration of CO to heme changes |
| We are protected to some extent against low level CO poisoning because: | The binding configuration of CO to heme iron favors oxygen binding |
| In the binding of oxygen to myoglobin, the relationship between the concentration of oxygen and the fraction of binding sites occupied can best be described as: | hyperbolic |
| When the dissociation constant (Kd) of any ligand is smaller by comparison, it means- | the ligand binds with higher affinity |
| In myoglobin's binding curve, the dissociation constant (Kd) is- | [Mb][O2]/[MbO2] |
| Which expression is the fraction of oxygen-bound myoglobin in solution (theta, or Y)? | pO2/pO2 + p50 |
| Which of the following properties is SHARED by both myoglobin and Hemoglobin? | They will both bind more O2 where it is more abundant, release O2 where it is more scarce |
| Myoglobin and Hemoglobin share the following properties EXCEPT: | They are both located in the blood’s red cells |
| The binding of one or more O2 ligands to a molecule of hemoglobin will induce: | an increased affinity for O2 in the remaining subunits (which have not yet bound O2). |
| When moving towards the lungs, hemoglobin shifts to the ____________ conformation, in which the Kd for oxygen binding is _________. | R; lowered |
| The Hills coefficient- | is larger when cooperativity is larger |
| The hypothesis that hemoglobin shifts between a low and a high affinity form implies that the protein- | Exists in two distinct conformations |
| The experimental proof for distinct T and R hemoglobin came from- | X-ray diffraction studies |
| Le Chatelier principle predicts that: | Oxygen will dissociate from hemoglobin where blood oxygen is low |
| When red blood cells migrate away from the lungs, initial oxygen dissociation from hemoglobin is stimulated by __________ and further on, dissociation is enhanced by _________: | Lower [oxygen]; T/R transition |
| When O2 binds to heme in hemoglobin, the _____ is drawn into the plane of the porphyrin, causing a conformational change that is transmitted to adjacent subunits, ________ the affinity for additional O2 binding. | Fe+2 atom; increasing |
| The initial trigger for conformational change in hemoglobin, leading to the T/R transition, involves | Shift in the porphyrins plane upon oxygen binding, from concave to planar |
| In the concerted model for cooperativity, the hemoglobins subunits- | change T to R or vice versa, all at once |
| Which of the following is NOT correct concerning 2,3-bisphosphoglycerate (BPG)? | It increases the affinity of hemoglobin for oxygen |
| BPG binding to hemoglobin requires that: | The protein will be in the T state |
| The physiological increase in the blood level of BPG is an adaptation to higher elevation because | - Hemoglobin has a reduced capacity to carry O2 in the capillaries - Hemoglobin's ability to bind O2 near the lungs remains virtually unchanged |
| Which of the following is the major form of hemoglobin produced in red blood cells during normal adult life? | alpha2/beta2 |
| In a fetus, Hemoglobin has gamma chains instead of beta chains. One difference is less positive charges in the central cavity of Hemoglobin. This increases the affinity of Hemoglobin to oxygen because: | BPG binds less tightly |
| In sickle-cell anemia, the gene coding for the beta-chain of hemoglobin shows- | A missense mutation leading to a substitution of Glu to Val |
| The graph below illustrates that (O2 Saturation Curve for hemoglobin): | As the curve shifts to the right, the affinity of hemoglobin to oxygen decreases |
| The following illustration demonstrates (Helix F) : | - That Heme exists in two possible configurations - That oxygen binding locks heme in one specific configuration - That the configuration of Helix F is affected by the configuration of the heme group |
| The following graph shows that (pO2 kPa) : | - BPG always decreases the binding of oxygen to hemoglobin - BPG always increases delivery of O2 to the tissues |
| Which of the answers is INCORRECT regarding the following molecule: a. binds better in adult hemoglobin than in fetal hemoglobin b. It binds both myoglobin and hemoglobin c. It has a role in modulating the binding of oxygen d. RBC's have it | It binds both myoglobin and hemoglobin |
| This question relates to the general mechanism described in the illustration: in the mechanism of trypsin, which amino acid plays the role of "B"? | Histidine 57 |
| The illustration below shows a mechanism that applies to the serine protease reaction. In the first part of the catalysis in trypsin or chymotrypsin (acylation phase), which species replaces the role of the water molecule? | Serine 195 |
| The graph below describes the energy profile of the reaction A → B. Which arrow(s) represent the activation energy? | 1 |
| In the mechanism of tyrosyl tRNA synthetase, the transition state is characterized by- | - The presence of both substrates at active site - The covalent bonding of 2 substrates to one another - 5 oxygen atoms covalently bound to a phosphorous atom - significant increase in the # of hydrogen bonds between the enzyme and the substrates. |
| The concept of "induced fit" refers to the fact that: | Initial substrate binding induces a conformational change in both the enzyme and substrate such that the two have increased non-covalent interaction. |
| In the following illustration the atom marked as "B" is: | general base |
| The "specificity pocket" in trypsin is designed to- | ensure that the peptide bond next to arginine or lysine will be cleaved |
| The activation energy of an enzyme-catalyzed reaction is the same for the forward and the reverse direction only when: | The (delta) G standard of the reaction is zero |
| Transition state stabilization in the mechanism of tyrosyl-tRNA synthetase is achieved by: | additional hydrogen bonding with the enzyme |
| In the following reaction that involves the active site of chymotrypsin, the molecule labeled "X" is: | A covalent inhibitor |
| In the mechanism of trypsin, the tetrahedral intermediate- | - is stabilized by non-covalent interactions in the oxyanion hol - contains the attacking nucleophile - is described as a transition state in the reaction - is characterized by a tetrahedral configuration of the peptide bond carbon. |
| The following illustration shows the active site of tRNA synthetase, enzyme part only, in two situations representative of the course of catalysis (I and II). Which of the following statements is/are TRUE regarding the configuration of state II? | State II could not exist without the substrate(s) present in the active site |
| In the following illustration the atom marked as "Y" is a | attacking nucleophile |
| Substrate and enzymes can interact with great specificity by engaging in which of the following non-covalent interactions? | Hydrogen bonds, Hydrophobic interactions, Ionic interactions |
| In the catalysis of a reaction, an enzyme: | increases the rate and decreases the activation energy of the reaction. |
| The transition state in any reaction mechanisms is: | State of highest potential energy |
| The serine-protease mechanism is an example of: | - general base catalysis - orientation and positioning of reactive groups in the active site - stabilization of the transition state - covalent catalysis |
| The following illustration shows which part of the chymotrypsin mechanism? | transition state |
| A transition state analog: | Has similar molecular shape to the substrate's transition state |
| The molecule illustrated below is: | Substrate/s in the transition state of tyrosyl tRNA synthetase |
| The specific site on the enzyme where __________ binds and catalysis occurs is called the _____________ site: | substrate; active |
| Enzymes are distinguished in their catalytic action from inorganic catalysts because enzymes: | have a strong specificity towards their substrates |
| The illustration below shows a step in the mechanism of one enzyme. Arrows point to specific functional groups. Which of the groups covalently react with each other in the following step of the mechanism? | Groups 3 and 4 |
| Which of the following is FALSE of the enzyme-substrate binding energy? | This is energy that is given off when the enzyme and substrate bind |
| The mechanism of "induced fit" is superior to the mechanism of "lock and key" because- | most of the binding energy is given off when the substrate reaches its transition state. |
| The illustration below shows two mechanisms for enzyme-substrate interaction. Which of the following statements is CORRECT? | Enzymes with the mechanism at the top are expected to have slower reaction rates in comparison to the ones at the bottom |
| Which of the following sequences of events in enzymes working by the induced-fit model? (*denotes the transition state) | E + S → ES → E*S* → EP → E + P |
| Which of the following factors can influence the rate of chemical reactions? | - frequency of collision - energy of collision - correct positioning of reactive groups - transition state stabilization |
| Activation energy is: | energy that must be added to get a reaction started, which is recovered as the reaction proceeds. |
| In enzyme-catalyzed reactions, the rate constant depends on which of the following factors: | Activation energy |
| The rate (velocity) of a reaction is- | The difference in product concentration divided by time |
| The reaction A + B → C + D is an example of- | Second-order reaction |
| For a reaction A + B ↔ C + D, the forward rate constant is K1 and the reverse rate constant is K-1. The rate (velocity) of the forward reaction is: | (K1)[A][B] |
| The rate constant of the reaction: | - Is a thermodynamic constant - Will be different for an enzyme-catalyzed versus |
| It is necessary to measure initial velocity (Vo) when seeking quantitative evaluation of enzyme catalysis because- | - As the reaction keeps going, the enzyme can become denatured - As the reaction keeps going, the substrate may be used up - As the rxn keeps going, the substrate may act as an inhibitor - As the rxn keeps going, the reaction may reach equilibrium |
| The Chart below shows the result of an enzyme experiment, where the concentration of product was measured at given time points. Which of the following choices BEST describes the reaction? | The reaction was going at initial velocity (Vo) at the 4 minute point |
| In the experiment described below, which of the following is TRUE? | Since we do not know what was the substrate concentration used, we cannot tell whether the enzyme was at Vmax |
| In the experiment shown, the 10 and 12 minute points represent | - The reaction might have reached equilibrium - The enzyme might have become denatured |
| When the Vmax and the Km of an enzyme are not known, it is essential to determine the enzyme's initial velocity (Vo) at different [S]. To determine the initial velocity, one would have to: | Measure the change of [P] vs time in the initial, linear phase of the experiment |
| Which of the following statements about a plot of Vo vs. [S] for an enzyme that follows Michaelis-Menten kinetics is FALSE? | As [S] increases, the initial velocity of reaction, Vo, always increases. |
| For the reaction A → B, ΔG = -60 kJ/mol. The reaction is started with 10 mmol of A. no B is initially present. After 24 hours, analysis reveals the presence of 0.2 mmol of B, 9.8 mmol of A. Which is the most likely explanation? | The activation energy for the reaction is very large; equilibrium has not been reached by 24 hours. |
| Michaelis and Menten assumed that the overall reaction for an enzyme-catalyzed reaction could be written as: E+S = ES>P - Using this reaction, the rate of breakdown of the enzyme-substrate complex can be described by the expression: | (K-1)[ES] + (K2)[ES] |
| When a reaction achieves a steady state: | The [ES] remains constant over time |
| The pre-steady state of a reaction is when: | The enzyme is first mixed with its substrate |
| The steady state assumption, as applied to enzyme kinetics, implies: | the ES complex is formed and broken down at equivalent rates. |
| An enzyme-catalyzed reaction becomes a zero-order reaction when- | [S] >>>> Km |
| We know that an enzyme works at initial velocity (Vo) equal to the Vmax when- | [S] >>> Km |
| An enzyme-catalyzed rxn was carried out with the sub. concentr. initially 1k times > the Km for that substrate.If, in a separate experiment, 2 as much sub. had been combined, how long would it take for the same amount of product to be formed? | 9 minutes |
| An enzyme-catalyzed reaction was carried out with the substrate concentration initially 1,000 times greater than the Km for that substrate.What is the velocity the enzymes in the two solutions were working at? | Vmax |
| The following data were obtained in a study of an enzyme known to follow Michaelis-Menten kinetics. The Km for this enzyme is approximately: | 5 mmole |
| The Lineweaver-Burk plot is used to: | solve, graphically, for the rate of an enzymatic reaction at infinite substrate concentration. |
| The number of substrate molecules converted to product in a given unit of time by a single enzyme molecule at saturation is referred to as the: | turnover number. |
| A small molecule that decreases the activity of an enzyme by binding to a site other than the catalytic site is termed a(n): | allosteric inhibitor. |
| In competitive inhibition, an inhibitor: | binds reversibly at the active site. |
| Vmax for an enzyme-catalyzed reaction: | is unchanged in the presence of a competitive inhibitor. |
| Below is a plot of Vo vs. [S] for a specific allosteric enzyme under different conditions. Which of the following best describes the graph? | Curve 3 represents the effect of a negative modulator added to #2 |
| To calculate the turnover number of an enzyme you need to know the: | - initial velocity of the catalyzed reaction at [S] >> Km. - enzyme concentration. |
| Which of the following is TRUE? When conducting an enzymatic reaction in vitro and checking for product formation at regular time intervals, the rate decreases after some time (the reaction curve levels off). This is because- | None of the above |
| Using the Lineaweaver plot, the lines of the competitively-inhibited and the non-inhibited reaction: | Intersect on the Y-axis |
| An inhibitor that binds the enzyme outside the active site, and has the same affinity to the free enzyme and the ES enzyme, will have the following effect on the reaction: | The Vmax is reduced but not the Km |
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awahay