UNE BIOCHEMISTRY MIDTERM REVIEW QUESTIONS WITH 100% CORRECT ANSWERS

Under low energy conditions, AMP will bind to phosphofructokinase I and glycogen phosphorylase at site unique to the active site. This enhances the activity of these enzymes. This is an example of which of the follow types of enzyme regulation? Allosteric activation An example of enzyme activation by cleavage is best illustrated by which of the following? Activation of chymotrypsinogen to chymotrypsin 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? Substrates or ligands that bind the active site 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 A 28-year-old male is recently diagnosed with HIV. As part of his treatment he is prescribed Nevirapine which interferes with retroviral reverse transcriptase enzyme. Using the graph below, which of the following best describes the impact of this drug on its target? It reduces the catalytic activity of the enzyme Which of the following is an example of enzyme regulation through covalent modification? Phosphorylation of muscle glycogen phosphorylase 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 residue. Phosphorylation of this amino acid is classified as which of the following? Covalent modification 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? The rate of the reaction is likely to decrease as the pH is out of optimal catalytic range 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 respect to the enzyme kinetics? The enzyme will require a lower substrate concentration to reach ½Vmax In the malate aspartate shuttle, glutamate is converted to _________ in the mitochondria while aspartate is converted to ___________ in the cytosol. α-ketoglutarate; oxaloacetate ATP is a high energy molecule that is often hydrolyzed during reactions. The energy within ATP is stored primarily in which of the following components of the molecule? In the high energy phosphate bonds Which of the following would be consistent with an exergonic reaction? ΔG0 would be negative The malate-aspartate shuttle is used to move reducing equivalents of cytosolic NADH into the mitochondria where it can be oxidized. Which of the following compounds is used to move the reducing equivalents from cytosolic NADH into the mitochondria? Malate Succinate is a substrate for which complex in the electron transport chain? Complex II (Succinate-Q reductase) Which of the following components of the electron transport chain passes electrons to O2 and causing it to be reduced to H2O? Cytochrome c oxidase Which of the following components of the electron transport chain is not bound to the mitochondrial membrane? CoQ ATP is used to carry energy within the cell. The majority of energy in ATP is stored within which of the following bonds indicated on the image below? 1 The glycerophosphate shuttle is the major shuttle of most tissues. Which of the following best describes the transfer of electrons by this shuttle? Electrons are directly transferred from glycerol 3-phosphate to an FAD containing glycerol phosphate dehydrogenase The fully reduced quinol form of CoQ contains which of the following combinations of electrons and protons? Two electrons and two protons Covalent catalysis is used by many enzymes to cleave peptide bonds. Which of the following amino acids would not facilitate this type of catalysis? (Think of the structure of the R-group of these amino acids) Valine How do most enzymes reduce the activation energy needed to move a reaction forward? Providing an active site most complementary the transition state 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? The presence of quaternary structure in hemoglobin 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 Chymotrypsin is a protease that cleaves peptide bonds. It is characterized as which of the following classes of enzymes? Hydrolases α-helices and β-sheets are primarily stabilized by which of the following interactions? Hydrogen bonding 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? Increase in 2,3 bisphosphoglycerate (BPG) 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 Movement of ammonia from an amino acid to an α-keto acid involves a family of enzymes best categorized as which of the following? Transferases Which of the following correctly pairs the amino acid with the TCA cycle intermediate it can be transaminated to? Glutamate: α-ketoglutarate A 10-year-old girl is swimming in a local competition. The intense exercise will increase intracellular calcium levels which in turn will increase flux through the TCA cycle by stimulating the activity of all of the following enzymes EXCEPT? Succinate thiokinase