Question 1

During fatty acid synthesis, malonyl-CoA becomes covalently attached to acyl-carrier protein via:

Accepted Answer

A)  ester-bond formation to a serine. 
B)  thioester-bond formation to a cysteine. 
C)  amide-bond formation to a lysine. 
D)  ether-bond formation to a serine. 
E)  thioester-bond formation to a prosthetic group. 
A)  ester-bond formation to a serine. 
B)  thioester-bond formation to a cysteine. 
C)  amide-bond formation to a lysine. 
D)  ether-bond formation to a serine. 
E)  thioester-bond formation to a prosthetic group.

Question 2

In comparing fatty acid biosynthesis with $\beta$oxidation of fatty acids, which statement is INCORRECT?

Accepted Answer

A)  A thioester derivative of crotonic acid (trans-2-butenoic acid) is an intermediate in the synthetic path, but not in the degradative path. 
B)  A thioester derivative of D-$\beta$-hydroxybutyrate is an intermediate in the synthetic path, not in the degradative path. 
C)  Fatty acid biosynthesis uses NADPH exclusively, whereas $\beta$ oxidation uses NAD+ exclusively. 
D)  Fatty acid degradation is catalyzed by cytosolic enzymes; fatty acid synthesis by mitochondrial enzymes. 
E)  The condensation of two moles of acetyl-CoA in the presence of a crude extract is more rapid in bicarbonate buffer than in phosphate buffer at the same pH; the cleavage of acetoacetyl-CoA proceeds equally well in either buffer. 
A)  A thioester derivative of crotonic acid (trans-2-butenoic acid) is an intermediate in the synthetic path, but not in the degradative path. 
B)  A thioester derivative of D-$\beta$-hydroxybutyrate is an intermediate in the synthetic path, not in the degradative path. 
C)  Fatty acid biosynthesis uses NADPH exclusively, whereas $\beta$ oxidation uses NAD+ exclusively. 
D)  Fatty acid degradation is catalyzed by cytosolic enzymes; fatty acid synthesis by mitochondrial enzymes. 
E)  The condensation of two moles of acetyl-CoA in the presence of a crude extract is more rapid in bicarbonate buffer than in phosphate buffer at the same pH; the cleavage of acetoacetyl-CoA proceeds equally well in either buffer.

Question 3

Which enzyme activity is NOT part of FAS II?

Accepted Answer

A)  a dehydratase 
B)  a thioesterase 
C)  a carboxylase 
D)  a transferase 
E)  a reductase 
A)  a dehydratase 
B)  a thioesterase 
C)  a carboxylase 
D)  a transferase 
E)  a reductase

Question 4

Which statement is FALSE regarding the formation of phosphatidylserine involving CTP activated intermediates in E. coli?

Accepted Answer

A)  The nucleophile is the OH at C3 of diacylglyceol. 
B)  CMP acts as a leaving group. 
C)  This is a nucleophilic substitution reaction. 
D)  A product of the reaction is a phosphodiester. 
E)  Loss of a phosphoanhydride makes this reaction energetically favorable. 
A)  The nucleophile is the OH at C3 of diacylglyceol. 
B)  CMP acts as a leaving group. 
C)  This is a nucleophilic substitution reaction. 
D)  A product of the reaction is a phosphodiester. 
E)  Loss of a phosphoanhydride makes this reaction energetically favorable.

Question 5

Synthesis of sphingosine from palmitoyl-CoA and serine requires which enzymatic class?

Accepted Answer

A)  transferases 
B)  oxidoreductases 
C)  hydrolases 
D)  ligases 
E)  All of these enzymatic classes are required. 
A)  transferases 
B)  oxidoreductases 
C)  hydrolases 
D)  ligases 
E)  All of these enzymatic classes are required.

Question 6

Which list ranks the compounds in order from the fewest to the greatest number of carbon atoms?

Accepted Answer

A)  acetate, cholesterol, mevalonate, squalene 
B)  acetate, mevalonate, squalene, cholesterol 
C)  mevalonate, cholesterol, squalene, acetate 
D)  acetate, squalene, mevalonate, cholesterol 
E)  acetate, mevalonate, cholesterol, squalene 
A)  acetate, cholesterol, mevalonate, squalene 
B)  acetate, mevalonate, squalene, cholesterol 
C)  mevalonate, cholesterol, squalene, acetate 
D)  acetate, squalene, mevalonate, cholesterol 
E)  acetate, mevalonate, cholesterol, squalene

Question 7

Which statement about cholesterol synthesis is TRUE?

Accepted Answer

A)  Cholesterol is the only known natural product whose biosynthesis involves isoprene units. 
B)  Only half of the carbon atoms of cholesterol are derived from acetate. 
C)  Squalene synthesis from farnesyl pyrophosphate results in the release of two moles of PPi for each mole of squalene formed. 
D)  The activated intermediates in the pathway are CDP-derivatives. 
E)  The condensation of two five-carbon units to yield geranyl pyrophosphate occurs in a "head-to-head" fashion. 
A)  Cholesterol is the only known natural product whose biosynthesis involves isoprene units. 
B)  Only half of the carbon atoms of cholesterol are derived from acetate. 
C)  Squalene synthesis from farnesyl pyrophosphate results in the release of two moles of PPi for each mole of squalene formed. 
D)  The activated intermediates in the pathway are CDP-derivatives. 
E)  The condensation of two five-carbon units to yield geranyl pyrophosphate occurs in a "head-to-head" fashion.

Question 8

The reaction sequence that leads to fatty acid synthesis includes (1) condensation, (2) first reduction reaction, (3) dehydration, and (4) second reduction. Show the first reduction reaction, with any required cofactors.

Accepted Answer

The first reduction reaction in the fatt

Question 9

All glycerol-containing phospholipids are synthesized from:

Accepted Answer

A)  cardiolipin 
B)  ceramide. 
C)  gangliosides. 
D)  mevalonate. 
E)  phosphatidic acid. 
A)  cardiolipin 
B)  ceramide. 
C)  gangliosides. 
D)  mevalonate. 
E)  phosphatidic acid.

Question 10

How does the energy cost of each round of fatty acid synthesis compare to each round of energy output from$\beta$ oxidation?

Accepted Answer

Fatty acid synthesis and fatty acid oxid

Question 11

If you perform fatty acid biosynthesis with CO2 labeled with 14C, where does the label end up in a fatty acid?

Accepted Answer

The label ends up in the carboxyl group

Question 12

Show the pathway from acetyl-CoA to mevalonate, indicating the roles of any cofactors.

Accepted Answer

The pathway from acetyl-CoA to mevalonat

Question 13

What statement is FALSE regarding the regulation of HMG-CoA reductase?

Accepted Answer

A)  HMG-CoA reductase is inhibited by phosphorylation. 
B)  Elevated levels of ATP will inhibit HMG-CoA reductase. 
C)  Elevated blood glucose will increase the activity of HMG-CoA reductase. 
D)  Statins act as competitive inhibitors for this enzyme. 
E)  Low cellular concentrations of cholesterol will increase expression of this enzyme and the LDL receptor. 
A)  HMG-CoA reductase is inhibited by phosphorylation. 
B)  Elevated levels of ATP will inhibit HMG-CoA reductase. 
C)  Elevated blood glucose will increase the activity of HMG-CoA reductase. 
D)  Statins act as competitive inhibitors for this enzyme. 
E)  Low cellular concentrations of cholesterol will increase expression of this enzyme and the LDL receptor.

Question 14

Reverse cholesterol transport is primarily associated with which lipoprotein?

Accepted Answer

A)  chylomicrons 
B)  VLDL 
C)  IDL 
D)  LDL 
E)  HDL 
A)  chylomicrons 
B)  VLDL 
C)  IDL 
D)  LDL 
E)  HDL

Question 15

When a 10-carbon unit and a 5-carbon unit condense to a 15-carbon intermediate in the pathway to cholesterol, the mechanism of condensation is basically different from that of the condensation of two 15-carbon units to the 30-carbon compound squalene. Describe the two condensations in enough chemical detail to illustrate the difference between them. (You should show relevant structures.)

Accepted Answer

The condensation of a 10-carbon unit and

Question 16

Describe two basic strategies for activating precursors in the biosynthesis of phospholipids.

Accepted Answer

The two basic strategies for activating

Question 17

Which statement is FALSE concerning bile salts?

Accepted Answer

A)  They are more amphipathic than cholesterol. 
B)  They are secreted in response to fat ingestion. 
C)  They are synthesized in the gall bladder. 
D)  They are sterol derivatives. 
E)  They typically carry a negative charge. 
A)  They are more amphipathic than cholesterol. 
B)  They are secreted in response to fat ingestion. 
C)  They are synthesized in the gall bladder. 
D)  They are sterol derivatives. 
E)  They typically carry a negative charge.

Question 18

A 30-carbon precursor of the steroid nucleus is:

Accepted Answer

A)  farnesyl pyrophosphate. 
B)  geranyl pyrophosphate. 
C)  isopentenyl pyrophosphate. 
D)  lysolecithin. 
E)  squalene. 
A)  farnesyl pyrophosphate. 
B)  geranyl pyrophosphate. 
C)  isopentenyl pyrophosphate. 
D)  lysolecithin. 
E)  squalene.

Question 19

Reduction of the gluconeogenesis intermediates dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (GAP) can generate glycerol-3-phosphate (G3P) as a product. Why does it make sense to use DHAP instead of GAP in G3P formation?

Accepted Answer

The formation of glycerol-3-phosphate (G

Question 20

Show the pathway from mevalonate to dimethylallyl pyrophosphate, indicating where any cofactors participate.

Accepted Answer

The pathway from mevalonate to dimethyla

Exam 21: Lipid Biosynthesis

During fatty acid synthesis, malonyl-CoA becomes covalently attached to acyl-carrier protein via:

In comparing fatty acid biosynthesis with β\betaβ oxidation of fatty acids, which statement is INCORRECT?

Which enzyme activity is NOT part of FAS II?

Which statement is FALSE regarding the formation of phosphatidylserine involving CTP activated intermediates in E. coli?

Synthesis of sphingosine from palmitoyl-CoA and serine requires which enzymatic class?

Which list ranks the compounds in order from the fewest to the greatest number of carbon atoms?

Which statement about cholesterol synthesis is TRUE?

The reaction sequence that leads to fatty acid synthesis includes (1) condensation, (2) first reduction reaction, (3) dehydration, and (4) second reduction. Show the first reduction reaction, with any required cofactors.

All glycerol-containing phospholipids are synthesized from:

How does the energy cost of each round of fatty acid synthesis compare to each round of energy output from β\betaβ oxidation?

If you perform fatty acid biosynthesis with CO2 labeled with 14C, where does the label end up in a fatty acid?

Show the pathway from acetyl-CoA to mevalonate, indicating the roles of any cofactors.

What statement is FALSE regarding the regulation of HMG-CoA reductase?

Reverse cholesterol transport is primarily associated with which lipoprotein?

Describe two basic strategies for activating precursors in the biosynthesis of phospholipids.

Which statement is FALSE concerning bile salts?

A 30-carbon precursor of the steroid nucleus is:

Reduction of the gluconeogenesis intermediates dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (GAP) can generate glycerol-3-phosphate (G3P) as a product. Why does it make sense to use DHAP instead of GAP in G3P formation?

Show the pathway from mevalonate to dimethylallyl pyrophosphate, indicating where any cofactors participate.

The Foundations of Biochemistry

Water

Amino Acids, Peptides, and Proteins

The Three-Dimensional Structure of Proteins

Protein Function

Enzymes

Carbohydrates and Glycobiology

Nucleotides and Nucleic Acids

DNA-Based Information Technologies

Lipids

Biological Membranes and Transport

Biosignaling

Bioenergetics and Biochemical Reaction Types

Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway

Principles of Metabolic Regulation

The Citric Acid Cycle

Fatty Acid Catabolism

Amino Acid Oxidation and the Production of Urea

Oxidative Phosphorylation and Photophosphorylation

Carbohydrate Biosynthesis in Plants and Bacteria

Biosynthesis of Amino Acids, Nucleotides, and Related Molecules

Hormonal Regulation and Integration of Mammalian Metabolism

Genes and Chromosomes

DNA Metabolism

RNA Metabolism

Protein Metabolism

Regulation of Gene Expression

Filters

In comparing fatty acid biosynthesis with $\beta$ oxidation of fatty acids, which statement is INCORRECT?

How does the energy cost of each round of fatty acid synthesis compare to each round of energy output from $\beta$ oxidation?

If you perform fatty acid biosynthesis with CO₂ labeled with ¹⁴C, where does the label end up in a fatty acid?