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Which amino acid is non-polar?
A) aspartate
B) arginine
C) threonine
D) lysine
E) valine |
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In the following peptide (angiotensin I), which amino acid is the carboxyl terminus?
Asn-Arg-Val-Tyr-Val-His-Pro-Phe-His-Leu |
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| Why is the peptide bond planar? |
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| B) It has partial double bond character, due to resonance. |
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| An acid with a pK of 5.0 is in a solution with a pH of 7.0. What is the ratio of the deprotonated to protonated form of the acid, [A-]/[HA]? |
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| 10. What is the net charge on glycine at pH 12? |
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| The structure of collagen is mostly: |
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| D) a stable arrangement of several secondary structure elements |
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You have a sample of a large protein (molecular weight = 100,000 kD). The protein is contaminated with several other proteins (molecular weights = 25,000 - 50,000 kD). Which of the methods below would separate the large protein from the small proteins?
A) Add 8 M urea and mercaptoethanol
B) SDS polyacrylamide gel electrophoresis
C) dialysis D) heat to 75oC E) none of these |
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| B) SDS polyacrylamide gel electrophoresis |
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Which of the following is a non-covalent interaction that stabilizes proteins in their biologically active folded state?
A) peptide bonds B) hydrogen bonds
C) acyl enzyme D) disulfide bonds
E) none of these |
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| Quaternary structure refers to: |
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| B) the spatial arrangements of subunits and the nature of their interactions |
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17. Which can form an ion pair with glutamate?
A) arginine B) valine C) cysteine D) serine
E) none of these |
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Which is most likely to occur in the interior of a protein folded into its native structure?
A) arginine B) valine C) cysteine D) serine
E) none of these |
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Which can form disulfide bonds?
A) arginine B) valine C) cysteine D) serine
E) none of these |
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If amino acid sequence determines 3D structure, how can divergent amino acid sequences produce structurally and functionally similar proteins? Identify the incorrect statement:
A) Conservative substitutions make sequences diverge without altering 3D structure and function
B) Only a few key parts of the structure are essential for function
C) Only a few key parts of the sequence are essential for determining the 3D structure
D) Unfolded proteins are as active as folded proteins
E) all statements are correct |
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| D) Unfolded proteins are as active as folded proteins |
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| Most unfolded proteins spontaneously refold to the biologically active state because: |
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| A) the free energy of the folded state is lower than the free energy of the unfolded state |
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| A non-polypeptide unit such as heme, bound to a protein, is called: |
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| Comparing hemoglobin and myoglobin, which properties are similar? |
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| The free energy of activation is: |
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| A) the energy difference between the substrate and the transition state. |
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| The value of KM is equal to the: |
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| B) substrate concentration when the reaction rate is half its maximal value. |
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| When substrate concentration is many times greater than KM, the reaction velocity is nearly equal to: |
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Which of the following is NOT a property of a typical enzyme active site?
A) a small part of the total enzyme structure.
B) a cleft or crevice.
C) formed from amino acids at widely separated regions of the sequence.
D) a mirror image of the inactive site, which is on the opposite side of the enzyme.
E) none of these |
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| D) a mirror image of the inactive site, which is on the opposite side of the enzyme. |
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| C) the amount of product per unit time produced by an enzyme with all active sites have substrate bound |
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| An enzyme has a maximum velocity of 10-5 M/sec at a total enzyme concentration of 10-8 M. What is the turnover number for this enzyme? |
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| An uncompetitive inhibitor: |
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| D) binds to the enzyme-substrate complex |
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| Which amino acids in chymotrypsin are found in the active site and are participants in substrate cleavage? |
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Which of the following is NOT a mechanism by which enzymes increase reaction rates?
A) causing the temperature of the substrate to increase
B) covalent intermediate
C) using substrate-binding energy
D) general acid-base catalysis
E) none of these |
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| A) causing the temperature of the substrate to increase |
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Which of the following contributes to the catalytic mechanism of chymotrypsin?
A) A zinc ion polarizes a water molecule
B) The oxyanion hole distorts the peptide carbonyl out of plane and stabilizes the tetrahedral intermediate
C) A magnesium ion polarizes a water molecule and positions it to attack the substrate
D) The enzyme undergoes a conformational change from the R state to the T state
E) none of these |
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| B) The oxyanion hole distorts the peptide carbonyl out of plane and stabilizes the tetrahedral intermediate |
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| What is the function of the catalytic triad of chymotrypsin? |
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| A) Converts the active site Ser into a powerful nucleophile |
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| In which regulatory mechanism is the final product of a pathway an inhibitor of the activity of the first step? |
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| When a molecule of O2 binds to one heme in deoxyhemoglobin |
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| D) it causes conformational changes which affect the other hemes |
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| Many allosteric enzymes have two types of subunits, termed: |
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| C) catalytic and regulatory |
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| The catalytic rate of an allosteric enzyme in the R form is _________ than the catalytic rate in the T form. |
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| The effects of substrate binding to one subunit of an allosteric enzyme on substrate binding to another subunit are referred to as _______ effects. |
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| When an enzyme catalyzes a reaction involving more than one substrate, a common reaction type is known as: |
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| Penicillin inhibits bacterial cell wall synthesis by: |
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| D) covalent modification of active site serine in glycopeptide transpeptidase |
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On the graph below, curve B represents the rate vs. substrate graph for ATCase in the absence of regulatory molecules. Which curve best represents the kinetics in the presence of the feedback inhibitor CTP?
C |
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| How is specificity determined by chymotrypsin? |
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| B) binding of a large, non-polar substrate side chain into a deep pocket on the enzyme |
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In the following peptide (angiotensin I), which amino acid is the amino terminus?
Asn-Arg-Val-Tyr-Val-His-Pro-Phe-His-Leu |
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Definition
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| An acid with a pK of 7.0 is in a solution with a pH of 5.0. What is the ratio of the deprotonated to protonated form of the acid, [A-]/[HA]? |
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| What is the net charge on glycine at pH 2? |
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Which of the following is a non-covalent interaction that stabilizes proteins in their biologically active folded state?
A) peptide bonds B) acyl enzyme
C) van der Waals interactions
D) disulfide bonds E) none of these |
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| C) van der Waals interactions |
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Which can form an ion pair with aspartate?
A) serine B) histidine C) leucine
D) cysteine E) none of these |
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Which is most likely to occur in the interior of a protein folded into its native structure?
A) serine B) histidine C) leucine
D) cysteine E) none of these |
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Which can form disulfide bonds?
A) serine B) histidine C) leucine
D) cysteine E) none of these |
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| Structural similarities between DNA and RNA include: |
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| D) linked by phosphodiester bonds in sugar-phosphate backbone |
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| Similarities between replication by DNA polymerase and transcription by RNA polymerase: |
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| Which is the least abundant RNA molecule? |
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| Which of the following is found in tRNA? |
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| B) a sequence complementary to mRNA codons |
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| Which of the following is true of the genetic code? |
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| What DNA sequence is complementary to 5'GAGCATGTTGGCCT 3'? |
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| Which is a protein-RNA complex? |
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| Mirror image molecules are called: |
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| An aldehyde and alcohol can react to form a: |
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Identify a non-reducing end of the polysaccharide below:
(B) |
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What is the relationship between these two molecules?
(enantiomers) |
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| Which amino acids are commonly linked to sugars in glycoproteins? |
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| B) serine, threonine, and asparagine |
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| Which of the following is a property of membranes? |
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| Which of the following is NOT a function of membranes: |
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Which of the following fatty acids has the most double bonds?
A) 18:0 B) 16:2
C) 16:1 D) 20:1
E) All of the above have the same number of double bonds |
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Which has the highest temperature of transition from ordered to fluid state?
A) 18:0 B) 16:2 C) 16:1 D) 20:1 E) All of the above have the same transition temperature |
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| Storage form of fatty acids: |
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| Unique functional properties of a particular membrane usually are properties of: |
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| C) specific membrane proteins |
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| A common structure found in membrane spanning proteins is: |
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| A) α helices of nonpolar amino acids that pass through the membrane |
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Which lipid is phosphatidyl choline?
(B) |
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ID integral membrane proteins:
C) a, b, and c |
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| An example of an active transport protein: |
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Secondary transport involves two substances: |
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Definition
A) one carried down its concentration gradient and a second carried against its
concentration gradient |
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| The selectivity filter of the K+ channel |
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| C) coordinates K+ but not Na+ |
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| Which of the following is a common second messenger? |
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| Identify the correct sequence of events in the activation of protein kinase A by signal transduction via epinephrine: |
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A) 1. epinephrine binds to β-adrenergic receptor; 2. G-protein exchanges GDP for GTP;
3. adenylate cyclase is activated; 4. cAMP binds to protein kinase A |
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| What is one mechanism for terminating signal transduction after it has been activated? |
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| B) G-protein hydrolyzes GTP to GDP |
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| After a receptor tyrosine kinase binds to a hormone on the extracellular side of the membrane, what is typically the next event in the signal transduction pathway? |
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| A) receptor dimerization and cross-phosphorylation |
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After a ligand binds to one type of 7TM receptor, the result is to activate
phospholipase C. What step does phospholipase C catalyze? |
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| C) phosphatidylinositol 4,5-bis-phosphate splits into IP3 and diacylglycerol |
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| How does cAMP activate protein kinase A? |
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| B) binds to regulatory subunit |
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| In the first stage of metabolism |
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| C) no useful energy is extracted |
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Which is an electron carrier?
A) biotin B) coenzyme A C) NADH D) ATP
E) none of these |
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Which can transfer phosphate to ADP to form ATP?
B)Creatine phosphate |
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| Fats have a higher chemical energy content than carbohydrates because fats are more: |
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| Why does ATP have a particularly large ΔGo for hydrolysis? |
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| A)charge repulsion destabilizes the γ-phosphate |
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How does coupling of reactions permit thermodynamically unfavorable reactions to
go spontaneously? |
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| B) The sum of the free energy changes of coupled reactions determines the overall spontaneity, so one highly favorable step can overcome some unfavorable steps |
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