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UNE biochemistry midterm review
Terms in this set (100)
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?
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?
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.
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?
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?
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?
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)
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?
α-helices and β-sheets are primarily stabilized by which of the following interactions?
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?
Which of the following correctly pairs the amino acid with the TCA cycle intermediate it can be transaminated to?
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?
TCA cycle intermediates are always being removed for various reasons but the cycle does not run out of intermediates and stop. This is because the TCA cycle can replenish intermediates through which of the following?
Using anaplerotic reactions
Pyruvate dehydrogenase complex is highly regulated. The enzyme will be most active when which of the following compounds is high?
A 2-day-old newborn male is diagnosed with congenital lactic acidosis because of a defective electron transport protein. This deficiency leads to a decrease in the rate at which NADH and FADH2 can be oxidized to produce ATP using oxidative phosphorylation and results in an increase in cytosolic AMP. Under these conditions which glycolytic enzyme would be stimulated?
Which of the following outlines the order of prosthetic groups as they are used for catalysis within the pyruvate dehydrogenase complex (PDC)?
Thiamine diphosphate → lipoamide → FAD
A deficiency in thiamine can reduce the activity of the pyruvate dehydrogenase complex. Under these conditions, you would expect to have a higher than normal blood concentration of which of the following metabolites?
Glycolysis provides intermediates that can be used to make other necessary substrates. One example of this is the direct conversion of pyruvate to which of the following amino acids?
What sequence of enzymes allows for the synthesis of glycogen from glucose-6-phosphate?
phosphoglucomutase, UDP-glucose pyrophosphorylase, glycogen synthase, amylo-(1,4α1,6)-transglycosylase
When insulin levels are high, which of the following is true?
Glycogen synthase is dephosphorylated and active
Which of the following enzymes is used by the gluconeogenic pathway but not the glycolytic pathway?
Phosphoenolpyruvate carboxykinase (PEPCK)
The skeletal muscle primarily provides substrate for gluconeogenesis through which of the following processes?
An individual is recently diagnosed with Type 2 diabetes. In this individual, hyperglycemia may in part be due to inactivity of which of the following glucose transporters on skeletal muscle?
If unregulated, which of the following pairs of enzymes would represent a futile cycle?
Fructose 1,6-bisphosphatase and phosphofructokinase-1
Which of the following events occurs during the formation of phosphoenolpyruvate from pyruvate during gluconeogenesis?
CO2 is required
Which of the following pathways provides the primary oxidizable fuel for skeletal muscle in the fasted state?
Lipolysis from adipose tissue
Which of the following pathways is not stimulated by high levels of insulin?
Amino acid catabolism
Which of the following statements is consistent with the actions of epinephrine?
Epinephrine enhances glucose output from the liver under stressful situations
Which of the following is a characteristic of all receptors?
They are specific to a chemical messenger
Shortly after a meal, there will be increased activity in which of the following pathways as a result of increased insulin?
A novel signaling cascade is discovered that you suspect activates a G-αs subunit. Which of the following downstream events would be consistent with this discovery?
Activation of adenylyl cyclase
Which of the following is an insulin insensitive GLUT transporter found primarily on the liver?
In the event that PI-3 kinase is not activated downstream of insulin, which of the following proteins would not be able to dock to the membrane?
Protein Kinase B
An 18-month-old is newly diagnosed with hereditary fructose intolerance (deficiency in Aldolase B). His mother reports he is particularly upset when he gets up in the morning or if he has not eaten in a while. Laboratory testing showed low blood glucose levels at the time of presentation. This presentation is likely due to an accumulation of fructose 1 -phosphate and inhibition of which of the following pathways?
Gluconeogenesis and glycogenolysis
A patient presents to the emergency department with lactic acidosis. A deficiency in thiamine (TPP) is suspected and this will be consistent with a decrease in the activity of following enzymes?
In the non-oxidative portion of the pentose phosphate pathway, 2-carbon fragments of keto-sugars can be transferred to other sugars to generate a larger sugar molecule. This reaction is catalyzed by which of the following enzymes?
A 2-week-old infant is brought to the emergency room due to extreme lack of energy, diarrhea, vomiting, jaundice, and an enlarged liver. The physician prescribed a switch from breast milk to infant formula containing sucrose as the sole carbohydrate. The baby's symptoms resolve within a few days. Which of the following was the most likely diagnosis?
Intolerance to dietary galactose
A 9-month-old girl is suffering from vomiting, lethargy, and poor feeding behavior. Her mother reports that the symptoms began shortly after the baby was given some cereal and mashed bananas by her grandparents. The baby's symptoms seemed to resolve after breastfeeding was resumed. Which of the following is the most likely diagnosis?
Intolerance to dietary fructose
A patient is newly diagnosed with a deficiency in fructokinase. Which of the following will not be a metabolic consequence of this deficiency?
Galactose 1-phosphate is initially converted to glucose 1-phosphate and requires which of the following compounds?
Which of the following metabolic shifts would reduce the activity of the glycolytic pathway?
A young women goes to work without eating breakfast and skips lunch. Which of the following pathways is providing substrates being used to generate ATP in the liver?
Free fatty acids
A deficiency in which of the following cofactors would result in decreased activity of the pyruvate dehydrogenase complex?
Propionate, a product of odd-chain fatty acid oxidation, will enter the TCA cycle as:
Alanine, transaminated to generate pyruvate, will replenish the TCA cycle through:
pyruvate carboxylase reaction
Citrate, can be shuttled out of the TCA cycle, and used in the process of:
fatty acid synthesis
What is not a substrate for gluconeogenesis?
During an overnight fast, which of the following is the major source of blood glucose?
In the pentose phosphate pathway, which intermediates can be regenerated back into glycolitic intermediates?
fructose-6-phosphate and glyceraldehyde 3-phosphate
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
Which of the following is the best description of primary protein structure?
a newly synthesized strand of amino acids
Prosthetic groups are complex nonprotein molecules that particitpate in catalysis by providing functional groups that form a covalent intermediate between the enzyme and substrate. Which of the following is an example of a coenzyme or cofactor that participates in a covalent catalysis reaction?
Which of the following best describes tertiary structure?
Interactions between alpha-helices and beta sheets to form a domain
As electrons flow through complexes in the inner mitochondrial membrane, protons are pumped from the matrix to the intermembrane space. Which of the following statements is most reflective of the pH in the intermembrane space?
the pH is higher in the matrix when compared to the intermembrane space
Heat can be generated in the brown adipose tissue of hibernating mammals. which of the following is the most likely mechanism by which this occurs?.
Expression of a protein that uncouples the ETC
Which of the following is a true statement with regards to the malate-aspartate shuttle systems?
Generates 2.5 molecules of ATP in mitochondria per each NADH from glycolysis
Which of the following enzymes is involved in the non-oxidative portion of the pentose pathway?
The major regulatory step of the pentose phosphate pathway is catalyzed by which enzyme?
glucose 6-phosphate dehydrogenase
A deficiency in glucose 6-phosphate dehydrogenase reduces levels of NADPH in the RBC. This leads to an increase in which of the following compounds with the cell?
RBC lack mitochondria; therefore glucose is primarily oxidized to ribose and which of the following compounds?
High levels of activity of the non-oxidative portion of the pentose phosphate pathway will directly produce intermediates of which of the following pathways?
Gylcogen degradation in the liver can be enhanced by elevated glucagon and the activation of a G-alpha-s receptor. The initial step in this cascade involves which of the following second messengers or active enzymes?
Which of the following best describes the role of the Cori cycle?
The process using lactate from skeletal muscle and red blood cells to generate glucose
Glycogenolysis and glycogen synthesis are regulated in such a way that neither process is active at the same time. During the fasted state, (ratio of insulin to glucagon is low). which of the following best characterizes the regulation of these pathways?
Both glycogen phosphorylase and glycogen synthase are phosphorylated
The process of gluconeogenesis primarily takes place in which of the following tissues?
When cortisol binds to its receptor, which of the following events occur to stimulate gluconeogenesis?
Enhanced transcription of regulatory enzymes
Which of the following would occur in the liver when glucose levels are high? (think insulin is elevated)
Generation of glucose 1-phosphate to be used for glycogen synthesis
A 1-month old boy is brought to the ER in a coma after sleeping through the night and failing to awaken in the morning. He is given IV glucose and awakens. Serum levels of pyruvate, lactate, and alanine are elevated, whereas oxaloacetate and aspartate levels are reduced. Which of the following is the most likely diagnosis in this patient?
Pyruvate carboxylase deficiency
Alanine can be shuttled from the skeletal muscle to the liver where it is deaminated to generate pyruvate. When glucagon is high, pyruvate is primarily used as a substrate for which of the following pathways?
Which of the following reactions is commonly used to replenish intermediates of the TCA cycle?
glutamate to alpha-ketoglutarate
A newborn is determined to have hyperinsulinemia. Which of the following is likely to occur as a result of this deficiency?
Increased activity of pyruvate kinase
In order for glucose to be retained within the cell, which of the following modifications must occur?
A farmer finds a cow dead in his field and notices an unusual plant nearby. Autopsy results show an elevated level of citrate present in the cow's mitochondria. This data collectively suggest inhibition of which of the following enzymes?
Which of the following best describes the net effect of the 8 steps of the TCA cycle?
this process completely oxidizes an acetyl group to carbon dioxide
After a meal, fructose 2,6-biphosphate levels are elevated. This compound will allosterically activate which of the following glycolytic enzymes?
Insulin stimulates fatty acid synthesis in the liver. These fatty acids are transported to the adipose tissue as which of the following?
Which of the following hormones is best described as anabolic?
What is the primary oxidized fuel for skeletal muscle in the fasted state?
Free fatty acids
A patient is found to have a rare disease in which the secretory function of the alpha cells of the pancreas is impaired. As a consequece, glucagon cannot be secreted. Direct stimulation of which of the following pathways in liver will be impaired?
Following insulin binding its receptor and autophosphorylation of the beta chain, what is the initial step in this cascade of events?
Recruitment of the insulin receptor substrate (IRS)
Recommended textbook explanations
Fundamentals of Biochemistry
Charlotte W. Pratt, Donald Voet, Judith G. Voet
Campbell Biology (AP Edition)
Cain, Campbell, Minorsky, Reece, Urry, Wasserman
Modern Biology: Student Edition
Janet L. Hopson, Postlethwait
Biocalculus: Calculus for the Life Sciences
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