UNE Biochemistry Midterm Exam 2025

How do most enzymes reduce the activation energy needed to move a reaction forward? - Correct Ans-Providing an active site most complementary the transition state An enzyme has a mutation within the substrate binding of the coenzyme needed for covalent catalysis. Which of the following is likely to result as a consequence of this mutation? - Correct Ans-The enzyme will not be able to form the transition state complex 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? - Correct Ans-The presence of quaternary structure in hemoglobin Cleavage of fructose 1,6-bisphosphate to dihydroxy and glyceraldehyde 3-phosphate is achieved by what class of enzymes? - Correct Ans-Lyase Domains are common structural elements that retain a particular function within the protein. Which of the following is an example of a protein domain? - Correct Ans-An arrangement of beta strands connected to alpha helices (BaBaB) Covalent catalysis is used by many enzymes to cleave peptide bonds. Which of the following amino acids would not facilitate this type of catalysis? - Correct Ans-Valine Which of the following proteins is likely to have quaternary structure? - Correct Ans-A multimeric protein that contains multiple peptide chains What of the following best describes a protein domain? - Correct Ans-A relatively large pattern a three-dimensional structure that is recognized across many proteins Movement of ammonia from an amino acid to an a-keto acid involved a family of enzymes best categorized as which of the following? - Correct Ans-Tranferases 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 a-helix structure to an aggregate of mostly B-sheets. This change in protein structure (leading to disease) is best attributed to changes in which of the following? - Correct Ans-Folding of the secondary structures Chymotropsin is a protease that cleaves peptide bonds. It is characterized as which of the following classes of enzymes? - Correct Ans-Hydrolases Which of the following best describes tertiary structure? - Correct Ans-Interactions between single amino acids adjacent to one another Hemoglobin has the ability to display cooperative binding while myoglobin does not display this binding pattern. Which of the following differences between the two proteins accounts for the difference in binding kinetics? - Correct Ans-The presence of quaternary structure in hemoglobin 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? - Correct Ans-Increase in 2,3 bisphosphoglycerate (BPG) 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? - Correct Ans-The enzyme will not be able to form the transition state complex An enzyme is participating in a general acid-base catalysis reaction with an optimal reaction pH of 6.0. If acid is added to the environment reducing the pH to 3, what is the likely impact to the rate of reaction? - Correct Ans-The rate of the reaction is likely to decrease as the pH is out of optimal catalytic range Which of the following best describes an enzyme inhibitor that increases the Km but does not change the Vmax? - Correct Ans-A competitive inhibitor 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? - Correct Ans-Increase DNA: histone association In the image below the blue line indicates enzyme kinetics with no inhibitor present. Based on this information which of the following is true? - Correct Ans-The green line shows enzyme kinetics with the addition of a noncompetitive inhibitor The following represents a series of reactions. As levels of B increase, this will decrease the conversion of S3 to B. Which of the following best describes this type of regulation in a biosynthetic pathway? - Correct Ans-Feedback inhibition Which of the following is an example of enzyme regulation through covalent modification? - Correct Ans-Phosphorylation of muscle glycogen phosphorylase Under low energy conditions, AMP will bind to phosphofructokinase 1 and glycogen phophorylase at a site unique to the active site. This enhances the activity of these enzymes. This is an example of which of the following types of enzyme regulation? - Correct Ans-Allosteric activation 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? - Correct Ans-Phosphorylation is a common covalent modification that can have various impacts on activity 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 cysteine removal from the cell. An effective therapy has been 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? - Correct Ans-Competitive inhibitors often look like the substrate and compete in the active site for binding Use the figure below to compare the activities of glucokinase and hexokinase. Based on this information, which of the following is a true statement? - Correct Ans-Glucokinase has a higher Km than hexokinase If a mutation is made within the active site of an enzyme resulting in a decrease in Km, which of the following will be true with