Exam 2 Flashcards
(46 cards)
G6P is produced by __________
the phosphorylation of free glucose, by glycogen degradation, and by gluconeogenesis (GNG)
G6P is a precursor for __________ and the ___________
glycogen synthesis and the pentose p pathway
The liver can hydrolyze G6P to __________
glucose
Glucose is metabolized by glycolysis to ________ which can be further broken down to __________ for oxidation by the citric acid cycle
pyruvate which is further broken down to acetyl coA
What are the precursors for Gluconeogenesis?
Lactate and pyruvate
How are the processes of glycogen synthesis and degradation, and glycolysis and gluconeogenesis related?
reciprocally regulated
What are the key concepts for Glycogen breakdown?
- Glycogen, the storage form of glucose, is a branched polymer - Glucose mobilization in the liver involves a series of conversions from glycogen to glucose-1-p to glucose-6-p and finally to glucose
Which of the following statements is incorrect?
A) Aerobically, oxidative decarboxylation of pyruvate forms a thioester that enters the
citric acid cycle.
B) High [acetyl-CoA] inhibits pyruvate DH and activates pyruvate carboxylase.
C) High [succinyl-CoA] inhibits both citrate synthase and -ketoglutarate (-KG) DH.
D) Reduction of pyruvate to lactate regenerates a cofactor essential for glycolysis.
E) All enzymes of the citric acid cycle are located in the mitochondrial matrix.
E) All enzymes of the citric acid cycle are located in the mitochondrial matrix.
Choose the incorrect statement regarding glucagon and epinephrine.
A) The cascade mechanism of epinephrine action is an example of signal transduction,
resulting in the release of glycogen breakdown in both the myocytes (skeletal muscle)
and the liver.
B) The skeletal muscle isozyme of pyruvate kinase is not inactivated in the presence of
elevated levels of [cAMP] so that glycolysis is stimulated (in the muscle) to produce
energy in the presence of the fight-or-flight hormone, epinephrine.
C) Glucagon stimulates gluconeogenesis and glycogen breakdown in the liver to maintain
glucose homeostasis in the blood.
D) Glucagon stimulates the glyoxylate cycle in the muscle to ensure adequate supply of
energy.
E) Both glucagon and epinephrine work through their specific membrane receptors and
trigger the signaling pathway(s) through a rise in [cAMP].
D) Glucagon stimulates the glyoxylate cycle in the muscle to ensure adequate supply of
energy.
Glycogen phosphorylase is a sensor of _________, which binds the enzyme allosterically to
promote its dephosphorylation.
A) AMP. B) Ca++. C) glucose. D) glucagon. E) GDP.
C - Glucose
Choose the incorrect statement.
A) The wavelength of the a peak is used to differentiate the various cytochromes in
mitochondrial membranes.
B) The electrons of NADH flows through Complex II, CoQ, Complex III, cytochrome c,
Complex IV to reach O2.
C) In bactriorhodopsin, a proton can be translocated by “hopping” along a chain of
hydrogen-bonded groups in a transmembrane channel, referred to as a proton wire.
D) Electron transfers over distances longer than ~14 Å always involve chains of redox
centers as in Complex I.
E) FMN and CoQ provide an electron conduit between the two-electron donor NADH and
the one-electron acceptors, the cytochromes.
B) The electrons of NADH flows through Complex II, CoQ, Complex III, cytochrome c,
Complex IV to reach O2.
Which of the following prokaryotes can produce the highest level of energy (G°’) for ATP
synthesis by oxidation of a reduced substrate (under standard conditions)?
A) Oxidation of NADH by nitrate as the terminal electron acceptor
B) Oxidation of acetate by sulfur (S) as the terminal electron acceptor
C) Oxidation of succinate by O as the terminal electron acceptor
D) Oxidation of ethanol by nitrate as the terminal electron acceptor
C) Oxidation of succinate by O as the terminal electron acceptor
Choose the incorrect statement.
A) In aerobic organisms, the citric acid cycle is an amphibolic pathway.
B) Succinyl-CoA is a precursor for heme biosynthesis.
C) Anaerobes lack alpha-ketoglutarate DH and therefore cannot carry out the complete citric
acid cycle.
D- alpha-KG is a precursor in a variety of biosynthetic pathways in both aerobic organisms and
anaerobes.
E) In the presence of malonate, one would expect malate to accumulate.
E) In the presence of malonate, one would expect malate to accumulate.
The two moles of CO2 produced in the first turn of the citric acid cycle have their origin in
the:
A) carboxyl and methylene carbons of oxaloacetate.
B) carboxyl group of acetate and a carboxyl group of oxaloacetate.
C) carboxyl group of acetate and the keto group of oxaloacetate.
D) two carbon atoms of acetate.
E) two carboxyl groups derived from oxaloacetate.
E) two carboxyl groups derived from oxaloacetate.
Which one of the following coenzymes (cofactors) of the pyruvate dehydrogenase complex
does not catalyze a redox reaction?
A) TPP B) Lipoamide C) CoA-SH D) FAD E) NAD+
C) CoA-SH
Choose the incorrect statement.
A) Insulin activates pyruvate DH phosphatase resulting in the stimulation of pyruvate DH
activity.
B) Citrate synthase is regulated by substrate availability, product inhibition, and
competitive feedback inhibition by intermediates further along the citric acid cycle.
C) Ca2+ activates pyruvate DH kinase and inhibits pyruvate DH phosphatase to downregulate
the activity of pyruvate DH.
D) alpha-KG DH is activated by Ca2+ and inhibited by succinyl-CoA.
E) Among organisms that don’t have all the genes for the citric acid cycle, the four
reactions leading from succinate to oxaloacetate function in reverse as electron
acceptors, resulting in the production of NAD+.
C) Ca2+ activates pyruvate DH kinase and inhibits pyruvate DH phosphatase to downregulate
the activity of pyruvate DH.
Gluconeogenesis must use “bypass reactions” to circumvent three reactions in the glycolytic
pathway that are highly exergonic and essentially irreversible. Reactions carried out by
which three of the enzymes listed must be bypassed in the gluconeogenic pathway?
1) Hexokinase 2) Phosphoglycerate kinase 3) Phosphofructokinase-1
4) Pyruvate kinase 5) Aldolase
A) 1, 2, 3 B) 1, 2, 4 C) 1, 4, 5 D) 1, 3, 4 E) 1, 2, 3, 4
D) 1, 3, 4
How many ATPs are produced by substrate level phosphorylation reactions when all the
carbons of one glucose molecule become CO2 by glycolysis and TCA cycle?
A) 2 B) 3 C) 4 D) 5 E) 6
E - 6
Almost all of the oxygen (O2) one consumes in breathing is converted to:
A) acetyl-CoA. D) water.
B) carbon dioxide (CO2). E) none of the above
C) carbon monoxide and then to carbon dioxide.
D) water.
Choose the incorrect statement about regulation of PP-1 in the hepatocytes.
A) Liver phosphoprotein phosphatase-1 (PP-1) is bound to glycogen through the
intermediacy through a glycogen binding subunit named GL.
B) The GL subunit of PP-1 is phosphorylated by an insulin-stimulated protein kinase,
resulting in the activation of the catalytic subunit of PP-1 (PP-1c).
C) Dephosphorylation (> 90%) of glycogen phosphorylase a relieves the inhibition of
hepatic PP-1.
D) Glycogen phosphorylase a in its R conformation effectively sequesters PP-1, which
can dephosphorylate P-Ser14 when phosphorylase a changes its conformation to the
T-state.
E) two of the above.
B) The GL subunit of PP-1 is phosphorylated by an insulin-stimulated protein kinase,
resulting in the activation of the catalytic subunit of PP-1 (PP-1c).
Uncoupling of mitochondrial oxidative phosphorylation:
A) allows continued mitochondrial ATP formation, but halts O2 consumption.
B) halts all mitochondrial metabolism.
C) halts mitochondrial ATP formation, but allows continued O2 consumption.
D) slows down the citric acid cycle.
E) slows the conversion of glucose to pyruvate by glycolysis.
C) halts mitochondrial ATP formation, but allows continued O2 consumption.
Which of the following statements about the chemiosmotic theory is false?
A) Electron transfer in mitochondria is accompanied by an asymmetric release of protons
on one side of the inner mitochondrial membrane.
B) Energy of e transfer in mitochondria is conserved as a electrochemical gradient of [H+]
(pmf = deltapH + delta ?).
C) Oxidative phosphorylation can occur in sonicated plasma membrane vesicles of heart
cells.
D) The sub-mitochondrial particles can synthesize ATP from ADP and Pi in the
suspension buffer of appropriate pH in the presence of succinate.
E) Electron transport occurs with the sub-mitochondrial particles and succinate even when
the F1 portion is gently removed from the ATP synthase.
C) Oxidative phosphorylation can occur in sonicated plasma membrane vesicles of heart
cells.
Choose the incorrect statement regarding cytochrome oxidase and ox phos.
A) A tyrosine residue at the active site of cytochrome c oxidase contributes an electron to
reduce O2 when two molecules of H2O are produced. (Note: There are other e donors.)
B) Cytochrome oxidase contains 2 hemes and 3 Cu ions in 2 binuclear centers.
C) Limited exposure to CN- is lethal for organisms due to comparatively few molecules of
cytochrome c.
D) Cytochrome oxidase receives electrons one at a time from cytochrome c.
E) When isolated mitochondria equilibrated at pH 9 are quickly transferred to a buffer of
pH 7 containing ADP and Pi, ATP synthesis occurs.
C) Limited exposure to CN- is lethal for organisms due to comparatively few molecules of
cytochrome c.
Individuals with a disease caused by a specific defect in the mitochondrial genome may
have symptoms ranging from mild to severe. This can be explained by _____ of
mitochondria (or mitochondrial DNA).
A) heteroplasmy B) homoplasmy C) exciton D) mitophagy E) apoptosis
A) heteroplasmy
