Exam 2

Question 1

G6P is produced by __________

Answer 1

the phosphorylation of free glucose, by glycogen degradation, and by gluconeogenesis (GNG)

Question 2

G6P is a precursor for __________ and the ___________

Answer 2

glycogen synthesis and the pentose p pathway

Question 3

The liver can hydrolyze G6P to __________

Answer 3

glucose

Question 4

Glucose is metabolized by glycolysis to ________ which can be further broken down to __________ for oxidation by the citric acid cycle

Answer 4

pyruvate which is further broken down to acetyl coA

Question 5

What are the precursors for Gluconeogenesis?

Answer 5

Lactate and pyruvate

Question 6

How are the processes of glycogen synthesis and degradation, and glycolysis and gluconeogenesis related?

Answer 6

reciprocally regulated

Question 7

What are the key concepts for Glycogen breakdown?

Answer 7

• 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

Question 8

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.

Answer 8

E) All enzymes of the citric acid cycle are located in the mitochondrial matrix.

Question 9

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].

Answer 9

D) Glucagon stimulates the glyoxylate cycle in the muscle to ensure adequate supply of
energy.

Question 10

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.

Answer 10

C - Glucose

Question 11

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.

Answer 11

B) The electrons of NADH flows through Complex II, CoQ, Complex III, cytochrome c,
Complex IV to reach O2.

Question 12

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

Answer 12

C) Oxidation of succinate by O as the terminal electron acceptor

Question 13

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.

Answer 13

E) In the presence of malonate, one would expect malate to accumulate.

Question 14

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.

Answer 14

E) two carboxyl groups derived from oxaloacetate.

Question 15

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+

Answer 15

C) CoA-SH

Question 16

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+.

Answer 16

C) Ca2+ activates pyruvate DH kinase and inhibits pyruvate DH phosphatase to downregulate
the activity of pyruvate DH.

Question 17

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

Answer 17

D) 1, 3, 4

Question 18

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

Answer 18

E - 6

Question 19

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.

Answer 19

D) water.

Question 20

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.

Answer 20

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).

Question 21

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.

Answer 21

C) halts mitochondrial ATP formation, but allows continued O2 consumption.

Question 22

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.

Answer 22

C) Oxidative phosphorylation can occur in sonicated plasma membrane vesicles of heart
cells.

Question 23

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.

Answer 23

C) Limited exposure to CN- is lethal for organisms due to comparatively few molecules of
cytochrome c.

Question 24

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

Answer 24

A) heteroplasmy

Question 25

One method used by newborn mammals to generate heat is referred to as nonshivering
thermogenesis. This method utilizes a protein channel called ________ which is present in
high levels inside the mitochondria of _____tissue.
A) thermogenin; muscle D) UCP-1; white adipose
B) UCP-1; muscle E) cytochrome oxidase; brown adipose
C) thermogenin; brown adipose

Answer 25

C) thermogenin; brown adipose

Question 26

Phosphate (Pi) is transported into the mitochondria from the cytosol by a phosphate carrier
which is driven by the
A) hydrolysis of ATP.
B) simultaneous transport of H+ into the mitochondrion.
C) simultaneous transport of ADP into the mitochondrion.
D) simultaneous transport of H+ out of the mitochondrion.
E) simultaneous transport of ATP out of the mitochondrion.

Answer 26

B) simultaneous transport of H+ into the mitochondrion.

Question 27

If acetyl-CoA is labeled with 14C at its methyl group, how many rounds of the citric acid
cycle are required for 14CO2 to be released?
A) 1 B) 2 C) 3 D) 4 E) no 14CO2 release ever

Answer 27

c - 3

Question 28

Citrate synthase and the NAD+-specific isocitrate DH are two key regulatory enzymes of
the citric acid cycle. These enzymes are inhibited by:
A) acetyl-CoA and fructose 6-phosphate. D) AMP and/or NAD+.
B) AMP and/or NADH. E) ATP and/or NAD+.
C) ATP and/or NADH.

Answer 28

C) ATP and/or NADH.

Question 29

If electron transfer in tightly coupled mitochondria is blocked (with antimycin A) between
cytochrome b and cytochrome c1, then:
A) all ATP synthesis will stop.
B) ATP synthesis will continue, but the P/O ratio will drop to one.
C) electron transfer from NADH will cease, but O2 uptake will continue.
D) electron transfer from succinate to O2 will continue unabated.
E) ATP is made, and the P/O ratio will rise.

Answer 29

A) all ATP synthesis will stop.

Question 30

A new compound isolated from mitochondria is claimed to represent a previously
unrecognized carrier in the electron transfer chain. It is given the name coenzyme Z.
Which line of evidence do you feel is the least conclusive in assigning this compound a
position in the electron transfer chain?
A) Alternate oxidation and reduction of the mitochondrion-bound coenzyme Z can be
readily demonstrated.
B) When added to a mitochondrial suspension, coenzyme Z is taken up very rapidly and
specifically by the mitochondria.
C) The rate of oxidation and reduction of mitochondrion-bound coenzyme is of the same
order of magnitude as the overall rate of electron transfer in mitochondria as measured
by oxygen consumption.
D) The reduction potential of Z is between that of two compounds known to participate in
the electron transport chain
E) Removal of coenzyme Z from the mitochondria results in a decreased rate of oxygen
consumption.

Answer 30

B) When added to a mitochondrial suspension, coenzyme Z is taken up very rapidly and
specifically by the mitochondria.

Question 31

Among the following energy cost (-) or yield (+), in ATP equivalents, for metabolic
processes, which one is incorrect?
A) glycogen (3 residues) to 6 pyruvate: +9 ATP
B) 3 glucose to 6 pyruvate (glycolysis): +6 ATP
C) 6 pyruvate to 3 glucose (gluconeogenesis): -12 ATP
D) 2 Asp to glucose (gluconeogenesis): -4 ATP
E) Glucose to CO2 and H2O (glycolysis through citric acid cycle and ox phos, glycerol-3-P
shuttle): +30 ATP

Answer 31

C) 6 pyruvate to 3 glucose (gluconeogenesis): -12 ATP

Question 32

The O2-consumption curve of a dilute, well buffered suspension of mitochondria containing
an excess of ADP and Pi takes the form A below. Which of the curve (B or C) represents
the experiment of adding amytal at t = 1 and then adding succinate at t = 2?
A) curve B B) curve C C) curve A

Answer 32

B) curve C

Question 33

The difference in pH between the internal and external surfaces of the inner mitochondrial
membrane is 0.75 pH units in actively respiring mitochondria. If the membrane potential is
0.15 V (inside negative), what is the free energy change on transporting 1 mol of protons
across the membrane from outside to inside at 25°C? (in kJ/mol)
A) +13.8 B) -13.8 C) +18.7 D) -18.7 E) -10.2

Answer 33

D) -18.7

Question 34

Why is it possible for electrons to flow from a redox center with a more positive X°’ to one
with a more negative X°’ within an electron-transfer complex? (Choose the incorrect
statement.)
A) The X may differ from X°’, depending on the redox center’s microenvironment.
B) The X may differ from X°’, depending on the concentrations of the e donors and
acceptors.
C) Such flow of electrons (more positive to more negativeX°’) is spontaneous according
to thermodynamics.

Answer 34

C) Such flow of electrons (more positive to more negativeX°’) is spontaneous according
to thermodynamics.

Question 35

The oxidation of a particular hydroxy substrate to a keto product by mitochondria has a P/O
ratio of less than 2. The initial oxidation step is very likely directly coupled to the:
A) oxidation of a flavoprotein. D) reduction of a pyridine nucleotide.
B) oxidation of a pyridine nucleotide. E) reduction of cytochrome a3.
C) reduction of a flavoprotein.

Answer 35

C) reduction of a flavoprotein.

Question 36

Many diabetics do not respond to insulin because of a deficiency of insulin receptor. What
happens to their blood glucose and muscle glycogen metabolism after a good meal?
(Choose the incorrect statement.)
A) Circulating [glucose] is high immediately after a meal.
B) Glucose transport into muscle cells (myocytes) won’t increase in the presence of high
blood glucose (no increase in GLUT4).
C) The GM subunit of PP-1 in the glycogen particles won’t be phosphorylated to activate
PP-1c (the catalytic subunit of PP-1).
D) Glycogen synthesis won’t be activated for lack of dephosphorylation of glycogen
synthase and for lack of glucose inside the muscle cells.
E) None of the above.

Answer 36

E) None of the above.

Question 37

What is (are) the metabolic fate(s) of pyruvate in a mammalian cell?
A) converted to lactate in homolactic fermentation.
B) converted to alanine by an aminotransferase
C) converted to acetyl-CoA by oxidative decarboxylation.
D) carboxylated to become oxaloacetate
E) All of the above

Answer 37

E) All of the above

Question 38

What happens to an individual with fructose-1,6-bisphosphatase deficiency?
A) The blood glucose level will be normal with regular dietary nutrients.
B) The blood glucose level will be low after a 24-hour fast because gluconeogenesis is
impaired.
C) The blood level of pyruvate will be elevated.
D) All of the above are true.
E) None of the above is true.

Answer 38

D) All of the above are true.

Question 39

Which of the enzymes is not required to convert mitochondrial succinyl-CoA to cytosolic
oxaloacetate used for gluconeogenesis?
A) Succinyl-CoA synthetase D) -KG DH
B) malate transporter E) fumarase
C) succinate DH

Answer 39

D) -KG DH

Question 40

Although animals cannot synthesize glucose from acetyl-CoA, if a rat is fed 14C-acetate,
some of the 14C label appears in glycogen extracted from its muscles.
A) True B) False

Answer 40

A - true

Question 41

Choose the incorrect statement.

A) Glycogen phosphorylase kinase is activated by phosphorylation and by Ca2+.
B) The alpha, beta, delta subunits of phosphorylase kinase have regulatory functions.
C) One of the subunits of phosphorylase kinase is a calmodulin.
D) The catalytic subunit of phosphorylase kinase in regulated by covalent modification
(phosphorylation/dephosphorylation).
E) An autoinhibitory segment binds to and blocks the phosphorylase kinase’s active site.

Answer 41

D) The catalytic subunit of phosphorylase kinase in regulated by covalent modification
(phosphorylation/dephosphorylation).

Question 42

Choose the incorrect statement.

A) There are two types of receptors for epinephrine on liver cells: the -adrenergic
receptor and the -adrenergic receptor.
B) Epinephrine promotes the release of glucagon from the pancreas, and glucagon binding
to its receptor on liver cells activated PKA through the cAMP pathway.
C) The second messenger from activating the -adrenergic receptor is cAMP.
D) Muscle cells do not respond to glucagon because of a lack of glucagon receptors.
E) When the [glucose] is high in muscle cells, phosphorylase a converts to its T state,
thereby leading to its dephosphorylation.

Answer 42

C) The second messenger from activating the -adrenergic receptor is cAMP.

Question 43

The first common metabolite among degradation of carbohydrate, amino acids, and fatty
acids is_________.
A) glucose-6-P B) acetyl-CoA C) GAP D) pyruvate E) fructose-6-P

Answer 43

B) acetyl-CoA

Question 44

39. Which of the following metabolites is prochiral?
    A) oxaloacetate B) succinate C) citrate D) fumarate E) isocitrate

Answer 44

C) citrate

Question 45

How many of the following terms is (are) not correct description of the structure and
mechanism for ATP synthesis by the F1Fo-ATP synthase? 1. C-ring, 2. binding change
mechanism, 3. Complex V, 4. High energy intermediate, 5. Pseudo-3-fold axis, 6. Rotor,
7. inner mitochondrial membrane, 8. peripheral membrane protein, 9. Open conformation
(O or E), 10.  subunit as a molecular camshaft.
A) 0 B) 1 C) 2 D) 3 E) 4

Answer 45

B) 1