Origins 1: MCQ 2 Flashcards
The oxidation of glucose under aerobic conditions is more efficient, in terms of ATP production, than under anaerobic conditions. Approximately how much faster would the rate of glucose utilization have to proceed in the absence of oxygen in order to produce an equivalent amount of ATP as that made under aerobic conditions.
About 15 times faster
The gluconeogenic pathway from pyruvate to glucose REQUIRES:
ATP and CO2
Cytosolic NADH
Both mitochondrial and cytosolic reactions
During active gluconeogenesis from pyruvate, CO2 is required for which reaction?
Pyruvate carboxylase
Which of the following statements is most likely to be FALSE?
A. Insulin can facilitate glucose uptake in muscle
B. GlucagoncanincreasethecytosolicconcentrationofcAMPinliver
C. Elevated levels of mitochondrial Ca2+ in muscle can inhibit the TCA cycle activity
D. A high NADH/NAD+ ratio in liver mitochondria can inhibit the TCA cycle activity
E. Strenuous muscle exercise with limited oxygen can elevate intracellular levels of lactate
C. Elevated levels of mitochondrial Ca2+ in muscle can inhibit the TCA cycle activity
Which statement about the pentose phosphate pathway is FALSE?
A. It can produce substrates for nucleotide synthesis from carbohydrates
B. It provides a means to produce NADPH for reductive biosynthesis
C. Glucose-6-phosphate is converted to ribose-5-phosphate
D. It provides a means to re-oxidize the cytosolic pool of NADH during active glycolysis
E. The pathway is active in the cytosol of liver
D. It provides a means to re-oxidize the cytosolic pool of NADH during active glycolysis
Which statement about cytochrome-c or its role in the electron transport chain is TRUE?
A. It is a small water-soluble protein attached to the outer surface of the inner mitochondrial
membrane.
B. It is the substrate for cytochrome-coxidase
C. It can accept electrons from Complex III
D.Its redox center contains a flavin mononucleotide
E. A, B, and C are correct
A, B, and C are correct
Which statement best describes the action of insulin in muscle?
It activates phosphoprotein phosphatase-1
Consider a preparation of respiring mitochondria that are provided an ample supply of succinate, ADP, and Pi. Oxygen is being consumed at a constant steady rate. Which statement best describes the results that will be observed upon addition of compound “X”, a known inhibitor of complex III?
ATP synthesis and oxygen consumption will cease
Which of the following reasons best explains why leucine and lycine are not substrates for gluconeogenesis in liver?
They are catabolized to acetyl-CoA
Caffeine inhibits cAMP phosphodiesterase. How does this affect the metabolic response to epinephrine?
It would prolong the effects of epinephrine through sustained activity of cAMP-dependent protein
kinases
A sample of liver glycogen is incubated with radio-labeled inorganic phosphate (32Pi), ATP, glycogen phosphorylase, and debranching enzyme. What are the products of this reaction? (Note: G1P = glucose-1-phosphate).
Approximately 10:1, 32P-labeled G1P: free glucose
In liver, all of the following may occur in response to increased levels of intracellular cAMP
1) Activation of phosphorylase kinase
2) Activation of glycogen phosphorylase
3) Activation of fluctose-2,6-bisphosphatase
4) Inhibition of phosphoprotein phosphatase-1
Which is the BEST reason why the glycerol phosphate shuttle will not operate, or will operate at a very slow rate, under anaerobic conditions?
Oxygen is required for the oxidation of the FADH2 cofactor for the mitochondrial glycerol
phosphate dehydrogenase enzyme
This is the substrate for complex IV in the electron transport chain
Cytochrome C
This is an inhibitor of Complex I (NADH dehydrogenase)
Rotenone
This is a small protein that is loosely attached to the outer surface of the inner mitochondrial membrane
and acts to accept electrons from Complex III during the electron transport process
Cytochrome C
This compound can transport protons across the inner mitochondrial membrane without passing through
the proton channel of ATP synthase
2,3-dinitrophenol
This small molecule is trapped within the inner mitochondrial membrane, but it is mobile and can
transport electrons to Complex III from Complexes I and II
Ubiquinone
The pentose phosphate pathway involves:
The oxidation of glucose-6-phosphate to ribose-5-phosphate with the production of 2 NADPH
Which statement describes the toxic mechanism of cyanide?
It is an inhibitor of cytochrome coxidase (ComplexIV)
Which statement about glycogen or its biosynthesis is FALSE?
A. It is stored as granuoles in the cytosol of muscle and liver cells
B. It has a highly branched structure and a molecular weight in the millions
C. It contains both α-1,4 and α-1,6 glycosidic-linked glucose monomers
D. A self glycosylating protein known as glucogenin provides a primer of glucose monomers to initiate
glycogen synthesis
E. It is synthesized in the mitochondria and then exported into the cytosol for storage
E. It is synthesized in the mitochondria and then exported into the cytosol for storage
Which “chemical strategy” is a common feature in the first two reaction steps for the biosynthesis of glucose from pyruvate (starting with the pyruvate carboxylase reaction), and the biosynthesis of fatty acids from acetyl-CoA (starting with the acetyl-CoA carboxylase reaction)?
Consumption of ATP, and carboxylation followed by decarboxylation
Consider an isolated system of mitochondria that are oxidizing pyruvate at a steady state with consumption of oxygen and production of ATP and CO2. What will happen if 2,4-dinitrophenol (an uncoupler) is added to the preparation? A. Oxygen consumption will increase B. ATP production will decrease C. Consumption of pyruvate will increase D. CO2 production will increase E. All of the above
E. All of the above
What are the NET products when 1 mole of acetyl-CoA is oxidized via the TCA cycle?
1 GTP + 1 FADH2 + 3 NADH + 2 CO2
