Biochem Chapter 24

jijepesa's version from 2017-06-01 13:07

Chapter 24

Question Answer
Fatty acid synthase (FAS) differs from β-oxidation in all of the following ways EXCEPT:
a. occurs in cytosol.
b. uses NADPH for oxidoreductase reactions.
c. acyl carrier protein linked intermediates.
d. all of the enzymes are on one polypeptide.
e. all are true.
What type of linkage occurs between ACP and the intermediates in fatty acid biosynthesis?
a. an ester
b. a thioester
c. an amide
d. an ether
e. an acetal
There is no transporter for acetyl-CoA to exit the mitochondria, so the carbons must be converted to ______ for transport to the cytosol.
a. acetone
b. butyrate
c. citrate
d. pyruvate
e. malonate
The main source(s) of NADPH for fatty acid biosynthesis is (are):
a. TCA cycle.
b. oxidative phosphorylation.
c. malic enzyme and the pentose phosphate pathway.
d. the conversion of OAA to malate by malate dehydrogenase.
e. glycolysis.
The reaction catalyzed by ______________ is: Citrate + ATP +CoA → acetyl-CoA + _____ + ___________.
a. citrate synthase; malate; AMP + Pi
b. citrate synthase; OAA; AMP + PPi
c. ATP-citrate lyase; OAA; AMP + PPi
d. ATP-citrate lyase; OAA; ADP + Pi
e. citrate synthase; OAA; ADP + Pi

Reducing equivalents derived from glycolysis in the form of NADH can be transformed into ________ for fatty acid biosynthesis by the combined actions of __________ and _____________.
a. NADPH; malate dehydrogenase; malic enzyme
b. NADPH; malate dehydrogenase; malic enzyme
c. ATP; malate dehydrogenase; malic enzyme
d. NADH; glyceraldehyde-3-phosphate dehydrogenase; malate dehydrogenase
e. NADPH; glyceraldehyde-3-phosphate dehydrogenase; malate dehydrogenase
The committed step in fatty acid biosynthesis, formation of malonyl-CoA, is catalyzed by:
a. fatty acid synthase.
b. pyruvate carboxylase.
c. propionate carboxylase.
d. acetyl-CoA carboxylase.
e. ATP-citrate lyase.
All are characteristic of acetyl-CoA carboxylase EXCEPT:
a. allosteric inhibition by palmitoyl-CoA.
b. biotin carboxylase and transcarboxylase subunits.
c. biotin carboxyl carrier protein subunits.
d. citrate shifts the enzyme toward the active polymer.
e. all are correct.
The coenzymes of acetyl-CoA carboxylase are:
a. biotin and ATP.
b. pyridoxal phosphate and TPP.
c. NADH and FAD.
d. TPP and folic acid.
e. FAD and Q.
Which of the following statements regarding phosphorylation of acetyl-CoA carboxylase is correct?
a. phosphorylation causes activation only in the presence of palmitoyl-CoA
b. phosphorylation is a result of glucagon binding to its receptor
c. high [citrate] inhibits the phosphorylated form
d. phosphorylation causes separation of the polymeric form of the enzyme to inactive protomers
e. both b and d are true
Acetyl-CoA carboxylase in animals is regulated by all of the following EXCEPT:
a. allosterically stimulated by citrate.
b. phosphorylation by protein kinase A.
c. allosterically inhibited by palmitoyl-CoA.
d. allosterically stimulated by ATP.
e. all are correct.
Phosphorylation of regulatory sites on acetyl-CoA carboxylase ________ the affinity for citrate and _________ the affinity for fatty acyl-CoAs requiring _______ levels of fatty acyl-CoAs for inhibition.
a. increases; decreases; low
b. decreases; increases; high
c. decreases; increases; low
d. increases; decreases; high
e. none are correct
Acyl carrier protein has the same _______________ group as the "business end" of __________________.
a. thiamin; TPP
b. biotin; acetyl-CoA carboxylase
c. phosphoadenosine; cAMP
d. pyridoxal phosphate; vitamin B6
e. phosphopantetheine; CoA
The formation of acetoacetyl-ACP is catalyzed by:
a. β-ketoacyl-ACP synthase (KSase).
b. acetyl-CoA carboxylase.
c. acetyl transacylase.
d. β-hydroxyacyl dehydratase.
e. β-ketoacyl reductase.
In fatty acid synthase, the correct sequence of enzyme catalyzed reactions are:
A. β-ketoacyl-ACP synthase
B. β-ketoacyl reductase
C. β-hydroxyacyl dehydratase
D. enoyl reductase
E. acetyl transferase
a. A, B, C, D, E
b. C, B, D, E, A
c. B, A, C, D, E
d. A, C, B, E, D
e. D, E, A, B, C
All are characteristic of fatty acid elongation EXCEPT:
a. acetyl-CoA additions.
b. uses both NADH and NADPH.
c. requires ATP and biotin.
d. occurs in cytosol and endoplasmic reticulum.
e. uses CoA rather than ACP.
Stearoyl-CoA desaturase has all of the following characteristics EXCEPT:
a. NADH and O2 are required.
b. produces a trans double bond.
c. involves cytochrome b5 reductase.
d. involves cytochrome b5.
e. occurs in the endoplasmic reticulum.
In E. coli, β-hydroxydecanoyl-ACP is dehydrated by β-hydroxydecanoyl thioester dehydrase to form a double bond _____ to the thioester in the ______ configuration which is further elongated to form _______________.
a. α,β; cis; palmitoyl-ACP
b. β,γ; cis; palmitoleoyl-ACP
c. β,γ; trans; palmitoleoyl-ACP
d. α,β; trans; palmitoleoyl-ACP
e. β,γ; cis; palmitoyl-ACP
E. coli does NOT have any _____________ fatty acids, plants can introduce double bonds into fatty acids between Δ9 and the ________-end of the chain, while mammals can only introduce double bonds between Δ9 and the _________-end of the chain.
a. saturated; carboxyl; methyl
b. mono-unsaturated; carboxyl; methyl
c. polyunsaturated; carboxyl; methyl
d. polyunsaturated; methyl; carboxyl
e. saturated; methyl; carboxyl
All of the following are characteristics of arachidonic acid EXCEPT:
a. it contains five cis-double bonds.
b. it is a precursor of leukotrienes and most prostaglandins.
c. it is an omega-6 fatty acid.
d. it can be synthesized from linoleic acid in mammals.
e. all are correct.
Regulation of fatty acid synthesis in humans is affected by all of the following EXCEPT:
a. malonyl-CoA binding to carnitine acyltransferase inhibits available substrate for β-oxidation.
b. citrate stimulates acetyl-CoA carboxylase.
c. acyl-CoAs are inhibitors of acetyl-CoA carboxylase.
d. insulin receptor binding maintains acetyl-CoA carboxylase in the inactive form.
e. glucagon promotes phosphorylation and inactivation of acetyl-CoA carboxylase.
Which of the following is correctly paired with its effect upon fatty acid synthesis?
a. palmitoyl CoA: activates
b. glucagon: activates
c. insulin: inhibits
d. citrate: activates
e. NADPH: inhibits
A lipid that does NOT have a sphingosine backbone is:
a. ganglioside GM1.
b. sphingomyelin.
c. phosphatidylinositol.
d. ceramide.
e. cerebroside.
_____________ are all derived from 20-carbon fatty acids that are acylated to membrane phospholipids and released by the enzyme _______________.
a. Arachadonates; triacylglycerol lipase
b. Arachadonates; phospholipase A1
c. Eicosanoids; phospholipase A1
d. Eicosanoids; phospholipase A2
e. Arachadonates; phospholipase A2
All are characteristics of eicosanoids EXCEPT:
a. derived from arachidonic acid.
b. exert their effects at very low concentrations.
c. usually act very near their site of synthesis.
d. include prostaglandins, thromboxanes and leukotrienes.
e. all are true.


Question Answer
Insulin promotes the _________ of acetyl-CoA carboxylase and __________ of triacylglycerol lipase by ____________ the phosphodiesterases that converts cAMP to AMP.
a. activation; inactivation; stimulating
b. inactivation; activation; stimulating
c. inactivation; activation; inhibiting
d. activation; inactivation; inhibiting
e. none are true
Both glycerol and dihydroxyacetone phosphate can serve as precursors for phosphatidic acid. Which enzyme is NOT USED to catalyze reactions in the synthesis of phosphatidic acid from these two precursors?
a. glycerol kinase
b. triose phosphate isomerase
c. acyldihydroxyacetone-P reductase
d. glycerol-3-phosphate acyltransferase
e. 1-acylglycerol-3-phosphate acyltransferase
CDP-diacylglycerols are precursors for the synthesis of all EXCEPT:
a. phosphatidylethanolamine.
b. phosphatidyl glycerol.
c. cardiolipins.
d. phosphatidylinositol.
e. all are true.
In eukaryotes, phosphatidic acid is converted directly either to _______ or to ________ from which all other ____________ are derived.
a. triacylglycerols; monoacylglycerols; acylglycerols
b. acylglycerols; phospholipids; glycerophospholipids
c. monoacylglycerols; phospholipids; glycerophospholipidsa
d. diacylglycerols; CDP-diacylglycerols; glycerophospholipids
e. diacylglycerols; CDP-diacylglycerols; acylglycerols
Components for plasmalogen biosynthesis include all EXCEPT:
a. CDP-ethanolamine.
b. fatty acyl-CoA.
c. NADPH, NADH and O2.
d. long-chain alcohol.
e. glycerol.
Platelet-activating factor displays dramatic ability to _________ blood vessels and thus _________blood pressure, and to aggregate platelets.
a. dilate; reduce
b. dilate; reduce
c. constrict; increase
d. constrict; increase
e. constrict; increase
The carbons of sphinganine are derived from:
a. palmitate and glycerol.
b. arachidonate and glycine.
c. fatty alcohol and dihydroxyacetone phosphate (DHAP).
d. palmitate and serine.
e. none of the above.
Sphinganine is acylated in the ______-position.
a. 3-OH
b. 2-NH2
c. 1-OH
d. 3-NH2
e. all are true