UNIT 1 - Quizzes and Exam, UNE medical biochemistry Unit 1 Test Correctly Answered To Score A+

UNIT 1 - Quizzes and Exam, UNE medical biochemistry Unit 1 Test Correctly Answered To Score A+ Which of the following amino acid would not be commonly found in the middle of a an α-helical domain? Proline. It is considered a 'helix breaker' and would not be found in an alpha helix; all other residues are nonpolar hydrophobic and could reside in a transmemebrane domain. Changes in the physiological variables listed below can alter the affinity of hemoglobin for oxygen. Which of the following will lower the affinity of hemoglobin for oxygen? a) decrease in protons b) increase in 2,3 bisphosphoglycerate (BPG) c) increase in pH d) decrease in CO2 Increase in 2,3 bisphosphoglycerate (BPG) A 22-year old female presents to the emergency department with acute abdominal pain. She indicates the pain came on rapidly in her mid-abdominal region. She has vomited several times over the last 4 hours. A diagnosis of acute pancreatitis is made and she is rushed to surgery. Elevation of which of the following serum enzymes would be consistent with this diagnosis? Amylase Which of the following is the best description of primary protein structure? A newly synthesized strand of amino acids Cleavage of fructose 1, 6-bisphosphate to dihydroxyacetone and glyceraldehyde 3-phosphate is achieved by what class of enzymes? Lyase Which of the following amino acid would not be commonly found in the middle of a an α-helical domain? Proline Domains are common structural elements that retain a particular function within the protein. Which of the following is an example of a protein domain? a) a prosthetic group such as heme b) irregular coils and loops c) an arrangement of β-strands connected by α- helixes d) a single α- helix An arrangement of β-strands connected by α-helixes α helices and β sheets are primarily stabilized by which of the following interactions? hydrogen bonding Hydrogen bonding is the primary stabilizing force in both secondary structures. In alpha helices the hydrogen bond is between the carbonyl oxygen group from one peptide bond and that amide hydrogen from a different peptide bond approximately amide 4 resides down in the helix. In beta sheets, the hydrogen bonding is between the carbonyl oxygen and the amide hydrogen from different peptide strands. Compare and contrast beta sheets and alpha helical formations. (Figure 7.3 vs. 7.5) Phosphorylation of an amino acid changes the charge on the residue to: Negative The addition of a phospho group will add a large negative moiety to the amino acid and change the functionality of the protein. Which of the following amino acid would not be commonly found in the middle of a an α-helical domain? Proline A 55-year old man is brought to the emergency room with a chief complaint of chest pain and tingling in his left arm. Elevation of which of the following enzymes in circulation would be most indicative of a myocardial infarction? Troponin A 22-year-old female is diagnosed with acute pancreatitis. Elevation of which of the following serum enzymes would be consistent with this diagnosis? a) lactate dehydrogenase b) amylase c) troponin d) creatine kinase amylase Hemoglobin binds oxygen with a greater affinity in the: R-State --- Hemoglobin binds oxygen with a greater affinity in the R state. As oxygen binds each subunit, the affinity for oxygen increases; this is termed cooperative binding. A 19-year-old boy is diagnosed with Creutzfeldt-Jakob Disease which is caused by the introduction of an amyloid fold in the disease-causing protein. The introduction of this fold causes the protein to transition from a primarily α-helical structure to an aggregate of mostly β-sheets. This change in protein structure (leading to disease) is best attributed to changes in which of the following? Folding of the secondary structures α-helices and β-sheets are primarily stabilized by which of the following interactions Hydrogen bonding Movement of ammonia from an amino acid to an alpha-keto acid involves a family of enzymes best categorized as: a) transferases b) ligases c) lyases d) isomerases transferases Which of the following proteins is likely to have quaternary structure? a) a protein that contains both α-helix and β-sheet secondary structures b) a multimeric protein that contains multiple peptide chains c) a small protein consisting of a single amino acid chain d) a large transmemberane protein with seven alpha helical domains a multimeric protein that contains multiple peptide chains A decrease in blood pH from 7.0 to 6.0 would be accompanied by which of the following changes in ion concentration? A 10-fold increase in hydrogen ion concentration- Explanation: The pH is the negative log of the hydrogen ion concentration, [H+]. At a pH of 7.0 [H+] is 10-7; and at pH 6.0[H+] is 10-6. The [H+] has changed by a factor of 10-6/10-7 which is 10. A decrease in 1 pH units is a 10 fold increase in [H+] Cleavage of fructose 1, 6-bisphosphate to dihydroxyacetone and glyceraldehyde 3-phosphate is achieved by what class of enzymes? Lyase A 55-year old man is brought to the emergency room with a chief complaint of chest pain and tingling in his left arm. Elevation of which of the following enzymes in circulation would be most indicative of a myocardial infarction? Troponin Which of the following is the best description of primary protein structure? A newly synthesized strand of amino acids Discriminate between primary, secondary, tertiary, and quaternary protein structure (Overview Figure 7.1) Hemoglobin bound to heme is termed a holoprotein. The heme or porphyrin ring is required for oxygen binding and it is defined as which of the following? Prosthetic group An enzyme has a mutation within the substrate binding site that reduces the binding of the coenzyme needed for covalent catalysis. Which of the following is likely to result as a consequence of this mutation? The enzyme will not be able to form the transition state complex Cleavage of fructose 1, 6 bisphosphate to dihydroxyacetone and glyceraldehyde 3-phosphate is achieved by what class of enzymes? a) ligase b) lyase c) transferase d) hydrolase Lyase Hemoglobin bound to heme is termed a holoprotein. The heme or porphyrin ring is required for oxygen binding and it is termed a: prosthetic group Hemoglobin or myoglobin bound to the heme prosthetic group is termed a holoprotein. Without the heme the protein is termed an apoprotein. Describe the structural difference between hemoglobin and myoglobin and compare O2 binding properties of hemoglobin and myoglobin (Figure 7.10 and 7.11) Which of the following is the best description of primary protein structure? A newly synthesized strand of amino acids Allosteric activators of hemoglobin will increase enzyme activity through which of the following mechanisms? Binding the enzyme, and keeping it in the "R" conformation Which of the following best describes the structure of heme? a) a planar porphyrin ring that binds iron b) a nicotinamide structure that is readily oxidized c) an n-linked glycosylation d) a negatively charged phosphate group a planar porphyrin ring that binds iron Prosthetic groups are complex nonprotein molecules that participate in catalysis by providing functional groups that form a covalent intermediate between the enzyme and the substrate. Which of the following is an example of a coenzyme or cofactor that participates in a covalent catalysis reaction? a) ATP b) OH- c) NADH d) pyridoxal phosphate pyridoxal phsophate Domains are common structural elements that retain a particular function within the protein. Which of the following is an example of a protein domain? An arrangement of β-strands connected by α-helices (βαβαβ) An enzyme has a mutation within the substrate binding site that reduces the binding of the coenzyme needed for covalent catalysis. Which of the following is likely to result as a consequence of this mutation? The enzyme will not be able to form the transition state complex Aspartate is classified as a: charged amino acid Aspartate (asp,D) is negatively charged and therefore acidic. List and name the 20 amino acids that commonly occur in proteins and classify them according to polarity, size, and charge At physiological pH (pH 7.4) carboxylic acids (COOH containing acids) are: approximately 100% dissociated The pKa of most carboxylic acids is between 2 and 5, therefore at pH 7.4 these acids are nearly fully dissociated. Define and explain pH, pKa, and the dissociation constant Ka A new enzyme is discovered that increases in activity when it is phosphorylated on an exposed tyrosine residue. Phosphorylation of this amino acid is classified as which of the following? Covalent modification Which of the following best describes tertiary structure? a) interactions between differing subunits of a protein b) interactions between α-helixes and β-pleated sheets to form a domain c) interactions between amino acids 4 residues away from each other d) interactions between single amino acids adjacent to one another interactions between α-helixes and β-pleated sheets to form a domain An α-helical arrangement of amino acids is considered to be part of what level of protein structure? a) Primary structure of the protein b) Secondary structure of the protein c) Tertiary structure of the protein d) Quaternary structure of the protein b The activity of an enzyme is increased when the enzyme is phosphorylated on an exposed tyrosine residue. Phosphorylation of this amino acid is classified as which of the following? Covalent modification Hemoglobin has the ability to display cooperative binding while myoglobin does not display this binding kinetic pattern. Which of the following differences between the two proteins accounts for this difference in binding kinetics? a) Differences in primary structure b) The presence of quaternary structure in hemoglobin c) The lack of tertiary structure in myoglobin d) Differences in secondary structure between the two proteins b In the image below the blue line indicates enzyme kinetics with no inhibitor present. Based on this information which of the following is true? The green line shows enzyme kinetics with the addition of a noncompetitive inhibitor Hemoglobin bound to heme is termed a holoprotein. The heme is required for oxygen binding and is defined as which of the following? a) apoprotein b) holoprotein c) heteroprotein d) prosthetic group prosthetic group The association of DNA and histones can be modified by histone acetylation. A decrease in histone acetylation will have which of the following impacts on the association of DNA and histones? Increase DNA: histone association Children with cystinosis have growth delay and renal issues to to accumulation of cysteine in cellular lysosomes. The defect involves a specific lysosomal membrane receptor that facilitates cysteine removal from the cell. An effective therapy involves administration of a drug with a similar structure to cysteine. This therapy reflects the general principle that competitive inhibitors typically resemble the structure of which of the following? a) substrates or ligands that bind the active site b) enzyme or receptor protein c) enzyme reaction products d) the cofactor substrates or ligands that bind the active site A 22-year old female presents to the emergency department with acute abdominal pain. She indicates the pain came on rapidly in her mid-abdominal region. Laboratory tests illustrate elevated levels of amylase. This result would indicate a dysfunction in which of the following organs? a) Pancreas b) Heart c) Liver d) Muscle a An enzyme inhibitor that increases the Km but does not change the Vmax is classified as: a competitive inhibitor Explanation: A noncompetitive inhibitor will characteristically increase the Vmax but have no effect on the Km as it does not interfere with substrate binding. Covalent modifications such as phosphorylation will change enzyme activity but in a manner such that enzyme is either active or inactive rather than impacting kinetics. An allosteric inhibitor is similar to a noncomepetitive inhibitor such that its presence makes it more difficult for the substrate to bind; in this case it is difficult for the subunits to be converted to the most active confirmation and the presence of the inhibitor usually increases Km and decreases Vmax. Children with cystinosis have growth delay and both renal and ocular issues due to accumulation of cysteine in cellular lysosomes. The defect involves a specific lysosomal membrane receptor that facilitates cystine removal from the cell. An effective therapy has been administration of a drug with a similar structure to cystine. This therapy reflects the general principle that competitive inhibitors typically resemble the structure of which of the following? Substrates or ligands that bind the active site Use the figure below to compare the activities of glucokinase and hexokinase. Based on this information, which of the following is a true statement? Glucokinase has a higher Km than hexokinase. A new enzyme is discovered that increases in activity when it is phosphorylated on an exposed tyrosine. Phosphorylation of this amino acid is classified as which of the following?