Study with the several resources on Docsity
Earn points by helping other students or get them with a premium plan
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Community
Ask the community for help and clear up your study doubts
Discover the best universities in your country according to Docsity users
Free resources
Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors
Biochemistry Final Exam Practice 63 Questions with Verified Answers
Typology: Exams
1 / 16
The central dogma of molecular biology teaches us that: a. RNA replicates itself and DNA is translated into protein b. RNA is typically the genetic material c. RNA contains information, which is translated into amino acid sequences d. Proteins are not needed to replicate DNA or transcribe RNA e. RNA is made of the same monomers as DNA - CORRECT ANSWER c. RNA contains information, which is translated into amino acid sequences Cell membranes are... a. ...aqueous partitions to keep the outside out and the inside in b. ...entirely greasy bilayers that allow proteins to be localized to particular compartments c. ...composed of amphipathic molecules with hydrophilic surfaces facing outside and inside d. ...surfaces assembled by membranase e. ...polymers of alternating carbohydrate and lipid monomers - CORRECT ANSWER c. ...composed of amphipathic molecules with hydrophilic surfaces facing outside and inside Hydrogen bonds are a. Weak associations in which protons are donated from a polar group to a hydrophobic group b. Irreversible associations in which hydronium maximizes its entropy c. Found in fluid water but not in DNA base pairs d. Donated, for example, from the C-alpha carbon of an amino acid to the carbonyl oxygen of another amino acid e. Donated, for example, from the amide proton of an amino acid to the carbonyl oxygen of another amino acid - CORRECT ANSWER e. Donated, for example, from the amide proton of an amino acid to the carbonyl oxygen of another amino acid At pH 4 a. There are 4000 hydronium molecules per liter of solution
b. There are 1000 times more hydronium molecules per liter than at neutral pH c. There are 3 times more hydronium molecules per liter than at neutral pH d. There are 1000 times more hydroxide ions per liter than at neutral pH e. There are 4 times fewer hydroxide ions per liter than at neutral ph - CORRECT ANSWER b. There are 1000 times more hydronium molecules per liter than at neutral pH At neutral pH, tyrosine has a. A protonated amino group, a deprotonated alcohol group, and a deprotonated carboxylic acid group b. A deprotonated amino group, a deprotonated alcohol group, and a protonated carboxylic acid group c. A net charge of - d. A net charge of zero e. A net charge of +1 - CORRECT ANSWER d. A net charge of zero The missing amino acid in the series Gly, ___, Ser is a. Met, because all have sulfur b. Ala, because it is a size series c. Asn, because the amino acids are carboxamides d. Lys, because they are the positively charged amino acids e. Arg, because they are the carbohydrate group of amino acids - CORRECT ANSWER b. Ala, because it is a size series Alpha helices a. Are the gene-rich regions of DNA b. Are always double-stranded c. Have their side chains on the inside d. Are glycine and proline-rich e. Have 3.6 amino acid residues per turn - CORRECT ANSWER e. Have 3.6 amino acid residues per turn Beta sheets have all of the properties below EXCEPT a. The property of twisting rather than lying in a flat plane b. Strands that can run either parallel or anti-parallel c. Location of side chains on alternating sides of the strand
d. Regular patterns of backbone hydrogen bonding between residues in the same strand e. Excluding proline from most positions - CORRECT ANSWER d. Regular patterns of backbone hydrogen bonding between residues in the same strand The fact that ribonuclease can refold after it is denatured indicates that a. A protein sequence encodes its three dimensional structure b. All sequences can form stable three dimensional structure c. Free thiol reagents only disrupt incorrect disulfide bonds d. Disulfide bonds always form the correct linkages the first time e. There are multiple, active conformations of ribonuclease - CORRECT ANSWER a. A protein sequence encodes its three dimensional structure Lactate dehydrogenase (LDH), purified to homogeneity from a cellular extract, had its specific activity increased by 200-fold. This suggests that a. The yield of LDH was 0.5% b. LDH might have constituted 0.5% of total protein in the cellular extract c. It is a multi-domain enzyme, whose subunit constitution is complex d. NADH was not produced in a linear fashion in these enzyme assays e. This LDH only works in one direction - CORRECT ANSWER b. LDH might have constituted 0.5% of total protein in the cellular extract Gel filtration chromatography works by a. Converting all proteins to detergent complexes with SDS b. Using a gel to link sugar to the target protein c. Native size separation d. Increasing salt concentration to elute proteins off columns e. Electrophoresis - CORRECT ANSWER c. Native size separation Antibodies have a variable region to recognize antigens that is a. made up of part of the heavy chain and part of the light chain b. entirely derived from the heavy chain c. entirely derived from the light chain d. all helical e. impossible to direct to a human antigen - CORRECT ANSWER a. made up of part of the heavy chain and part of the light chain
Which of the following is a TRUE statement? a. Enzymes force reactions to proceed in only one direction b. Enzymes alter the equilibrium of the reaction c. Enzymes alter the standard free energy of the reaction d. Holoenzymes are functional without a cofactor e. None of the above is true - CORRECT ANSWER e. None of the above is true Which statement best describes the relationship between ΔG° and ΔG?′ a. They are both determined only by the temperature of the reaction b. They are described by changes in Keq c. They account for differences between the standard state and the physiological or actual concentrations of reactants and products d. They are dependent on the mechanism of the reaction e. They are equal to each other at pH 7 - CORRECT ANSWER c. They account for differences between the standard state and the physiological or actual concentrations of reactants and products Which statement about an enzyme-substrate interaction is FALSE? a. It is a reversible interaction b. Specificity is due to the three dimensional structure of the enzyme c. It promotes formation of the transition state d. The "Lock-and-key" model best describes enzyme-substrate interaction e. It occurs through multiple weak interactions - CORRECT ANSWER d. The "Lock- and-key" model best describes enzyme-substrate interaction Which of the following is CORRECT about the Michaelis constant (Km): a. It is unique for each enzyme and is dependent on enzyme concentration b. It varies for enzymes and substrates c. K. = k-1 / k d. It is a measure of the rate of catalysis for a particular substrate e. It is equal to the concentration of substrate at which all the enzyme active sites are occupied - CORRECT ANSWER b. It varies for enzymes and substrates In the Lineweaver-Burk (double-reciprocal) plot, the x-intercept is equal to: a. -1/Km b. 1/Km c. Km/Vmax
d. 1/Vmax e. -1/Vmax - CORRECT ANSWER a. -1/Km A critical feature of the Michaelis-Menten model of enzyme catalysis is: a. Increasing the probability of product formation b. Shifting the reaction equilibrium c. The formation of an intermediate ES complex d. Reactants have a lower energy than products e. None of the above is correct - CORRECT ANSWER c. The formation of an intermediate ES complex How is substrate specificity determined by chymotrypsin? a. By binding a hydrophobic amino acid into a deep pocket in the enzyme b. By the interaction of the catalytic amino acids with the substrate c. By binding of the N-terminus at the active site d. Through covalent binding of a histidine residue to the substrate e. By a conformational change upon the binding of substrate - CORRECT ANSWER a. By binding a hydrophobic amino acid into a deep pocket in the enzyme An enzyme has an optimal pH of 8 that is entirely due to two amino acid residues in the active site. What two amino acids are most likely responsible for this observation? a. Glycine and alanine b. Aspartate and histidine c. Glutamate and alanine d. Arginine and lysine e. None of the above are likely to be responsible - CORRECT ANSWER b. Aspartate and histidine An inhibitor changes the Km and Vmax values of an enzyme reaction to the same extent. What statement below best describes the results of a double-reciprocal plot when comparing the enzyme alone to the enzyme plus inhibitor? a. 1/Vmax values are identical b. The ratio of Km/Vmax is larger with inhibitor c. 1/Km values are identical d. The plot of 1/V0 vs 1/[S] for the two cases results in lines with identical slopes
e. This is an irreversible reaction - CORRECT ANSWER d. The plot of 1/V0 vs 1/[S] for the two cases results in lines with identical slopes Which of the following statements is CORRECT for hemoglobin and oxygen transport? a. The oxygen binds to the proximal histidine residue of the globin chain b. Bonding of carbon dioxide to hemoglobin molecules increases the binding of oxygen c. Hemoglobin binds more oxygen as the pH is lowered d. Hemoglobin binds more oxygen at higher BPG concentrations e. The binding of each O2 molecule to hemoglobin increases its affinity for the next O2 molecule - CORRECT ANSWER e. The binding of each O2 molecule to hemoglobin increases its affinity for the next O2 molecule Which of the following describes the Bohr effect? a. Lowering the pH and increasing the partial pressure of CO2 results in the release of O2 from oxyhemoglobin b. Increasing the pressure of CO2 results in the release of O2 from oxyhemoglobin c. Binding of 2,3-BPG and lowering the pH increases the T form of hemoglobin d. Increasing the pH and partial pressure of CO2 results in the release of O2 from deoxyhemoglobin e. None of the above are correct - CORRECT ANSWER a. Lowering the pH and increasing the partial pressure of CO2 results in the release of O2 from oxyhemoglobin Which of the following statements BEST describes the following equilibrium? CO
c. Blood groups illustrate the effects of glycosyltransferases d. Monosaccharides are either ketone or aldehyde molecules with alcohol groups e. Cellulose is a polysaccharide of fructose - CORRECT ANSWER e. Cellulose is a polysaccharide of fructose Which of the following statements is FALSE? a. Milk sugar is cleaved by lactase b. Glycogen is a polysaccharide that serves as a glucose storage in animal cells c. Mucins are glycoproteins that act as lubricants d. The N-linkage of glycoproteins is formed by attaching carbohydrates to the amine group of any amino acid e. The stability of a protein can be enhanced by glycosylation - CORRECT ANSWER d. The N-linkage of glycoproteins is formed by attaching carbohydrates to the amine group of any amino acid Choose the answer that BEST describes glycolipids. a. They serve as hormones b. They are derived from glycerol c. They contain phosphorylchlorine d. They are oriented in membranes with the sugar residue always on the extracellular side e. They are not amphipathic - CORRECT ANSWER d. They are oriented in membranes with the sugar residue always on the extracellular side Which of the following statements about mammalian triacylglycerols is TRUE? a. They are stored in the nucleus of mammalian cells b. They are a storage form of fatty acids c. They contain a glucose molecule d. They are energy rich, oxidized and hydrophobic e. They are formed by attaching fatty acids to a molecule of glycerol through other bonds - CORRECT ANSWER b. They are a storage form of fatty acids Membrane fluidity in animals depends on: a. Chain length of its lipids b. Extent of unsaturation of constituent fatty acids c. Cholesterol content d. Number of cis double bonds of constituent fatty acids
e. All of the above play a role in membrane fluidity - CORRECT ANSWER e. All of the above play a role in membrane fluidity Which of the following statements is FALSE? a. Integral membrane proteins are embedded in the membrane b. Integral membrane proteins can be released by changing the pH of the membrane's environment c. Peripheral membrane proteins are bound to membranes by electrostatic or hydrogen-bonds d. Peripheral membrane proteins may be bound to the surface of integral proteins e. Membrane proteins undergo lateral diffusion - CORRECT ANSWER b. Integral membrane proteins can be released by changing the pH of the membrane's environment Select the statement that is TRUE a. Glucose is transported into animal cells by a symporter b. Pumps require energy to move molecules with their concentration gradient c. Channels move molecules against their concentration gradient d. Active transport through a secondary transporter is driven directly by the hydrolysis of ATP e. All of the above are incorrect - CORRECT ANSWER a. Glucose is transported into animal cells by a symporter Which of the following BEST completes the following statement to make it TRUE? cGMP, inositol 1,4,5-triphosphate (IP3), diacylglycerol (DAG) are all a. primary messengers b. second messengers c. membrane receptors d. effectors e. found in the cell membrane - CORRECT ANSWER b. second messengers Pick the ending to the following statement that makes it TRUE. β-adrenergic receptor is a. a dimeric receptor that recruits protein kinases b. a dimeric receptor that is a protein kinase c. a seven-transmembrane-helix receptor
d. activated by binding of the growth hormone e. down regulated by phosphorylation - CORRECT ANSWER c. a seven- transmembrane-helix receptor Which of the following steps does NOT contribute to insulin-induced uptake of glucose? a. Phosphatidylinositide 3-kinase converts PIP2 to PIP3 (3,4,5) b. PIP3-activated kinase activates Akt c. Akt inhibits Ca2+ release activating GLUT4 transporter d. PIP3 activates PIP3-activated kinase e. Increased glucose transporter on cell surface - CORRECT ANSWER c. Akt inhibits Ca2+ release activating GLUT4 transporter Which of the following statements about digestion is TRUE? a. α-amylase is the first enzyme to start digesting starch b. The first step of protein digestion is trypsin hydrolyzing proteins in the stomach c. Lipases convert fatty acids to triacylglycerol d. Digested sugars form into micelles before transport through the blood stream e. Proteins eaten as food are commonly scavenged and reused by the body without digestion - CORRECT ANSWER a. α-amylase is the first enzyme to start digesting starch Pick the BEST ending for the following statement: Zymogens are a. synthesized in the liver b. inactivated by protease digestion c. active enzymes d. active only in low pH e. inactive proteases - CORRECT ANSWER e. inactive proteases Which of the following hypothetical drug treatments could cause weight gain by disrupting caloric homeostasis after eating? a. A drug that inhibits growth hormone receptor activation b. A drug that inhibits the release of zymogens from the pancreas c. Taking a dietary supplement that contains biotin, niacin (nicotinic acid), and riboflavin with each meal d. A drug that reduces the release of bile salts from the gallbladder
e. A drug that reduces the release of cholecystokinin (CCK) - CORRECT ANSWER e. A drug that reduces the release of cholecystokinin (CCK) Which of the following statements is TRUE? a. ATP must be constantly regenerated to keep the body supplied with energy b. ATP has the highest phosphoryl-transfer potential of phosphorylated compounds c. ATP hydrolysis is endergonic d. ATP contains one phosphoanhydride bond e. Glycerol 3-phosphate (G3P) can transfer its phosphoryl group to ADP from ATP
c. pyruvate and phosphoenolpyruvate d. enolase and 2-phosphoglycerate e. glyceraldehyde-3-phosphate and pyruvate - CORRECT ANSWER a. glyceraldehyde-3-phosphate and dihydroxyacetone phosphate Oxidation in glycolysis converts NAD+ to NADH. Which of the following is a FALSE statement about the mechanisms used by living organisms to regenerate NAD+ for glycolysis? a. Pyruvate is converted to ethanol b. Microorganisms regenerate NAD+ without oxygen c. Pyruvate is converted to lactate d. NAD+ is generated during gluconeogenesis for use in glycolysis e. Pyruvate is oxidized to CO2 and H2O - CORRECT ANSWER d. NAD+ is generated during gluconeogenesis for use in glycolysis Pick the BEST ending for the following statement: Glycolysis helps pancreatic beta cells regulate glucose through a. The increase of ATP concentration b. Closing of K+ channels c. Influx of Ca2+ d. Insulin secretion e. All of the above - CORRECT ANSWER e. All of the above A key step of gluconeogenesis is conversion of pyruvate to phosphoenolpyruvate. Which of the following statements about this conversion is true? a. Pantothenate is a required cofactor for pyruvate carboxylase b. Malate is an intermediate of this conversion c. The conversion requires hydrolysis of two ATP molecules d. Conversion of pyruvate to phosphoenolpyruvate occurs in the cytoplasm e. Conversion of pyruvate to phosphoenolpyruvate in gluconeogenesis is an unfavorable reaction (has a positive ∆G) - CORRECT ANSWER b. Malate is an intermediate of this conversion Which of the following reactions in glycolysis or gluconeogenesis is NOT regulated? a. Conversion of fructose-6-phosphate to fructose-1,6-phosphate by phosphofructose kinase
b. Conversion of glucose to glucose-6-phosphate by hexokinase c. Conversion of 3-phosphoglycerate to 1,3-biphosphoglycerate by phosphoglycerate kinase d. Conversion of pyruvate to oxaloacetate by pyruvate carboxylase e. Conversion of fructose 1,6-phosphate to fructose 6-phosphate by fructose 1,6- bisphosphatase - CORRECT ANSWER c. Conversion of 3-phosphoglycerate to 1,3- biphosphoglycerate by phosphoglycerate kinase Which of the following statements about the Cori cycle is TRUE? a. It is used to regenerate reducing potential for muscles b. It allows lactate generated in muscle to be used to generate glucose c. It generates amino acids to rebuild muscles damaged during exercise d. It is disrupted in type 2 diabetes e. It is the process by which Queen Elizabeth of Great Britain gets new dogs - CORRECT ANSWER b. It allows lactate generated in muscle to be used to generate glucose Cellular reverse transcriptase describes the enzymatic activity of which of the following enzymes? a. DNA polymerase b. Exonuclease c. Telomerase d. Primase e. Topoisomerase - CORRECT ANSWER c. Telomerase Which of the following activities is NOT shared by E. coli DNA polymerase I and DNA polymerase III? a. A proofreading activity b. A 5' to 3' polymerase activity c. A progressive and fast rate of DNA synthesis d. A 5' to 3' exonuclease activity e. A 3' to 5' exonuclease activity - CORRECT ANSWER d. A 5' to 3' exonuclease activity Which of the following statements BEST describes lagging strand synthesis in DNA replication? a. Is coordinated with leading strand synthesis
b. Involves DNA polymerization in the 5' to 3' direction c. Uses an RNA primer d. Requires DNA ligase e. All of the above are characteristics of lagging strand synthesis - CORRECT ANSWER e. All of the above are characteristics of lagging strand synthesis In growing cells, unrepaired spontaneous determination of cytosine is associated with: a. No change in DNA sequence because base pairing is unaltered b. A change in DNA sequence from a CG base pair to a TA base pair c. A change in DNA sequence from a CG base pair to an AT base pair d. A change in DNA sequence from a CG base pair to a GC base pair - CORRECT ANSWER b. A change in DNA sequence from a CG base pair to an TA base pair Base excision repair involves: a. Cleavage of both strands of the DNA b. Repair by DNA polymerase III c. The action of the ABC exinuclease d. Formation of an apurinic or apyrimidic site e. All of the above - CORRECT ANSWER d. Formation of an apurinic or apyrimidic site Which of the following statements about genetic mutations and DNA repair is TRUE? a. Errors in DNA replication can cause mutations b. Pyrimidine dimers are repaired using the mismatch repair pathway c. The Ames test identifies mutagens that cause double-strand DNA breaks d. All cellular repair pathways require a DNA polymerase e. Base excision repair can repair double-strand DNA breaks - CORRECT ANSWER a. Errors in DNA replication can cause mutations Which of the following mutations in the cis-elements of the lac operon will be associated with the HIGHEST level of transcription, when E. coli is grown in the presence of lactose but not glucose? a.Mutation of the Repressor binding site so Repressor binds tighter b. Mutation of the translation initiation codon to a stop codon c. Mutation of the translation initiation codon to a Leu codon
d. Mutation of the Catabolite activator protein (CAP) binding site so CAP does not bind e. Mutation of the -35 region to change the sequence to match consensus - CORRECT ANSWER e. Mutation of the -35 region to change the sequence to match consensus Which of the following statements about E. coli RNA polymerase is FALSE: a. Binds DNA using the σ subunit b. Binds DNA using the α subunit c. Initiates RNA synthesis without a primer d. Uses the coding strand as a template e. Synthesizes RNA in the 5' to 3' direction - CORRECT ANSWER d. Uses the coding strand as a template Which of the following statements about transcription in E. coli is TRUE? a. Transcriptional regulation is coordinated by organizing protein coding regions into operons b. Catabolite activator protein (CAP) links transcriptional regulation with glucose levels in the growth media (environment) c. RNA polymerase transcribes all RNAs d. Promoter recognition is rate limiting e. All of the above - CORRECT ANSWER e. All of the above Acetylation of the histone tail _____. a. inactivates transcription of the target gene b. enhances histone tail-DNA interactions c. enhances histone tail-general transcription factor interactions d. neutralizes the positive charge on histone e. does not affect the efficiency of RNA polymerase recruitment - CORRECT ANSWER d. neutralizes the positive charge on histone RNA Polymerase III: a. Transcribes mRNA b. Transcribes the 28S RNA c. Transcribes tRNAs d. Does not require a promoter for initiation of transcription e. All of the above - CORRECT ANSWER c. Transcribes tRNAs
Which of the following best describes Tata binding protein (TBP)? a. Binds the Initiator element in RNA polymerase II promoters b. It is required for transcription initiation of RNA polymerase II c. Is required for double-strand break repair d. It is part of the TFIIH complex e. Is responsible for transcriptional repression - CORRECT ANSWER b. It is required for transcription initiation of RNA polymerase II In eukaryotes, the following enzyme(s) play(s) a role in tRNA processing: a. RNase P b. CCA-adding enzyme c. Endonuclease d. Ligase e. All of the above - CORRECT ANSWER e. All of the above Which snRNP is required for branchpoint recognition? a. the U1 snRNP b. the U2 snRNP c. the U6 snRNP d. the 5.5S RNA e. None of the above - CORRECT ANSWER b. the U2 snRNP The carboxyl-terminal domain of the largest subunit of RNA polymerase II: a. Contains the RNA polymerase II active site b. Undergoes acetylation during initiation c. Coordinates transcription with RNA processing d. Contains a repeat of basic amino acids that helps RNA polymerase II recognize DNA e. Is NOT required for transcription of mRNA - CORRECT ANSWER c. Coordinates transcription with RNA processing Which of the following is NOT a characteristic of the genetic code? a. It is degenerate b. It is universal c. It has no punctuation between codons d. It is non-overlapping
e. It is read in triplets - CORRECT ANSWER b. It is universal Amino acyl - CORRECT ANSWER