Question 1

Explain briefly why we require fats in our diets.

Accepted Answer

Dietary fats provide the linol

Question 2

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

Accepted Answer

There will not be any radioact

Question 3

Explain the triacylglycerol cycle and how drugs such as rosiglitazone (Avandia)promote this cycle and help lower fatty acid levels in the bloodstream.

Accepted Answer

The triacylgycerol cycle is the constant

Question 4

The enzyme system for adding double bonds to saturated fatty acids requires all of the following except:

Accepted Answer

A) a mixed-function oxidase. 
B) ATP. 
C) cytochrome b5. 
D) molecular oxygen (O2). 
E) NADPH. 
A) a mixed-function oxidase. 
B) ATP. 
C) cytochrome b5. 
D) molecular oxygen (O2). 
E) NADPH.

Question 5

Lipoprotein particles in human blood do not contain:

Accepted Answer

A) an apolipoprotein B isoform. 
B) cholesterol. 
C) cholesteryl esters. 
D) lecithin. 
E) triglycerides. 
A) an apolipoprotein B isoform. 
B) cholesterol. 
C) cholesteryl esters. 
D) lecithin. 
E) triglycerides.

Question 6

Shown below is a molecule of squalene,which is composed of 6 isoprene units.Draw lines to indicate the junctions between the six isoprene units.

Accepted Answer

The answer of Shown below is a molecule of squalene,which...

Question 7

Fatty acid synthesis and fatty acid breakdown occur by similar pathways.Describe,very briefly,four ways in which the synthetic and breakdown pathways differ.

Accepted Answer

Fatty acid synthesis (in any order)
(1)e

Question 8

Which of these can be synthesized by plants but not by humans?

Accepted Answer

A) Linoleate [18:2($\Delta$9,12)] 
B) Palmitate (16:0) 
C) Phosphatidylcholine 
D) Pyruvate 
E) Stearate (18:0) 
A) Linoleate [18:2($\Delta$9,12)] 
B) Palmitate (16:0) 
C) Phosphatidylcholine 
D) Pyruvate 
E) Stearate (18:0)

Question 9

In E.coli the synthesis of phosphatidylethanolamine directly involves:

Accepted Answer

A) acyl carrier protein. 
B) biotin. 
C) CDP-choline. 
D) phosphatidylglycerol. 
E) serine. 
A) acyl carrier protein. 
B) biotin. 
C) CDP-choline. 
D) phosphatidylglycerol. 
E) serine.

Question 10

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 11

Which of the following is derived from a sterol?

Accepted Answer

A) Bile salts 
B) Gangliosides 
C) Geraniol 
D) Phosphatidylglycerol 
E) Prostaglandins 
A) Bile salts 
B) Gangliosides 
C) Geraniol 
D) Phosphatidylglycerol 
E) Prostaglandins

Question 12

Describe the process by which cholesterol esters in the bloodstream enter cells.

Accepted Answer

The process is receptor-mediated endocyt

Question 13

Which of the following does not contribute to lowering the risk of atherosclerosis?

Accepted Answer

A) Statin drugs 
B) HDL 
C) Reverse cholesterol transport 
D) ApoA-I 
E) Foam cells 
A) Statin drugs 
B) HDL 
C) Reverse cholesterol transport 
D) ApoA-I 
E) Foam cells

Question 14

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 the 10-carbon gerany

Question 15

What are plasma lipoproteins? What is their general role in mammalian metabolism?

Accepted Answer

Plasma lipoproteins are protein-lipid ag

Question 16

Describe briefly the four stages in the pathway from acetyl-CoA to lanosterol.

Accepted Answer

(1) synthesis of mevalonate from acetate

Question 17

Sketch the pathway from arachidonate to thromboxanes and explain how aspirin blocks the synthesis of thromboxanes.

Accepted Answer

(See Fig. 21-15.) As

Question 18

Which of the following is not required in the synthesis of fatty acids?

Accepted Answer

A) Acetyl-CoA 
B) Biotin 
C) HCO3- (CO2) 
D) Malonyl-CoA 
E) NADH 
A) Acetyl-CoA 
B) Biotin 
C) HCO3- (CO2) 
D) Malonyl-CoA 
E) NADH

Question 19

The biosynthesis of triacylglycerols from acetate occurs mainly in:

Accepted Answer

A) animals but not in plants. 
B) humans after ingestion of excess carbohydrate. 
C) humans with low carbohydrate intake. 
D) plants but not in animals. 
E) None of the above 
A) animals but not in plants. 
B) humans after ingestion of excess carbohydrate. 
C) humans with low carbohydrate intake. 
D) plants but not in animals. 
E) None of the above

Question 20

Which of these statements about the regulation of cholesterol synthesis is not true?

Accepted Answer

A) Cholesterol acquired in the diet has essentially no effect on the synthesis of cholesterol in the liver. 
B) Failure to regulate cholesterol synthesis predisposes humans to atherosclerosis. 
C) High intracellular cholesterol stimulates formation of cholesteryl esters. 
D) Insulin stimulates HMG-CoA reductase. 
E) Some metabolite or derivative of cholesterol inhibits HMG-CoA reductase. 
A) Cholesterol acquired in the diet has essentially no effect on the synthesis of cholesterol in the liver. 
B) Failure to regulate cholesterol synthesis predisposes humans to atherosclerosis. 
C) High intracellular cholesterol stimulates formation of cholesteryl esters. 
D) Insulin stimulates HMG-CoA reductase. 
E) Some metabolite or derivative of cholesterol inhibits HMG-CoA reductase.

Exam 21: Lipid Biosynthesis

Explain briefly why we require fats in our diets.

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

Explain the triacylglycerol cycle and how drugs such as rosiglitazone (Avandia)promote this cycle and help lower fatty acid levels in the bloodstream.

The enzyme system for adding double bonds to saturated fatty acids requires all of the following except:

Lipoprotein particles in human blood do not contain:

Shown below is a molecule of squalene,which is composed of 6 isoprene units.Draw lines to indicate the junctions between the six isoprene units.

Fatty acid synthesis and fatty acid breakdown occur by similar pathways.Describe,very briefly,four ways in which the synthetic and breakdown pathways differ.

Which of these can be synthesized by plants but not by humans?

In E.coli the synthesis of phosphatidylethanolamine directly involves:

A 30-carbon precursor of the steroid nucleus is:

Which of the following is derived from a sterol?

Describe the process by which cholesterol esters in the bloodstream enter cells.

Which of the following does not contribute to lowering the risk of atherosclerosis?

What are plasma lipoproteins? What is their general role in mammalian metabolism?

Describe briefly the four stages in the pathway from acetyl-CoA to lanosterol.

Sketch the pathway from arachidonate to thromboxanes and explain how aspirin blocks the synthesis of thromboxanes.

Which of the following is not required in the synthesis of fatty acids?

The biosynthesis of triacylglycerols from acetate occurs mainly in:

Which of these statements about the regulation of cholesterol synthesis is not true?

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

Recombinant Dna Technology

Lipids

Biological Membranes and Transport

Biosignaling

Principles of Bioenergetics

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

Integration and Hormonal Regulation of Mammalian Metabolism

Genes and Chromosomes

Dna Metabolism

Rna Metabolism

Protein Metabolism

Regulation of Gene Expression

Filters

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