Deck 12: Lipid Metabolism

Question 1

How many acetyl-CoA's are required to synthesize one molecule of isopentenyl pyrophosphate?

A) 1
B) 2
C) 3
D) 4
E) 5

Answer 1

C

Question 2

___________ is used to transport fatty acids into the mitochondria.

A) Carrone
B) Phytate
C) Creatine
D) Carnitine
E) Acyl carrier protein

Answer 2

D

Question 3

The $\beta$ -oxidation of fatty acids requires_________.

A) Coenzyme A
B) FAD
C) NAD⁺
D) Both A and C are correct
E) All of the above are correct

Answer 3

All of the above are correct

Question 4

_________, a product of the oxidation of odd-chain fatty acids, is converted to succinyl-CoA.

A) Malonyl-CoA
B) Propionyl-CoA
C) Acetyl-CoA
D) Oxaloacetate
E) Acyl carnitine

Question 5

_______ derive a substantial amount of energy from the oxidation of odd-chain fatty acids.

A) Plants
B) Fungi
C) Ruminants
D) Humans
E) Microorganisms

Question 6

The carbon atoms of cholesterol are derived from _______.

A) Oxaloacetate
B) Succinyl CoA
C) Erythrose
D) Acetyl CoA
E) More than one response is correct

Question 7

The following reaction requires the presence of _________.

A) Carnitine
B) CoASH
C) NAD⁺
D) FAD
E) Water

Question 8

In animals the function of peroxisomal $\beta$ -oxidation appears to be

A) Energy generation
B) Gluconeogenesis
C) Synthesis of very long fatty acids
D) Degradation of branch chain fatty acids
E) Shortening of very long chain fatty acids

Question 9

The acetyl-CoA derived from glyoxysomal $\beta$ -oxidation is converted to carbohydrate via

A) The glyoxylate cycle
B) The citric acid cycle
C) Gluconeogenesis
D) Both A and B are correct
E) Both A and C are correct

Question 10

Refsum's disease results from a buildup of ________in nerve tissue.

A) Epoxides
B) Ketone bodies
C) Odd chain fatty acids
D) Phytanic acids
E) Carnitine

Question 11

Which of the following is not one of the ketone bodies?

A) Acetoacetate
B) $\beta$ -Hydroxybutyrate
C) $\beta$ -Methylglutarate
D) Acetone
E) None of the above is correct

Question 12

Most eicosanoids are derived from ________acid.

A) Stearic
B) Monohydroperoxyeicosatetraenoic
C) Linolenic
D) Arachidonic
E) Arachidic

Question 13

Glycerol from the hydrolysis of triacylglycerols is transported by the blood to the ____

A) Intestine
B) Stomach
C) Liver
D) Pancreas
E) A and B

Question 14

The intermediates in fatty acid synthesis are linked through a ________linkage to ACP.

A) Thioester
B) Amide
C) Ester
D) Acetal
E) Ether

Question 15

Saturated fatty acids containing up to 16 carbon atoms are assembled in ________.

A) Mitochondria
B) Rough endoplasmic reticulum
C) Smooth endoplasmic reticulum
D) Peroxisomes
E) Cytoplasm

Question 16

Fatty acid synthesis begins with the carboxylation of acetyl CoA to form
________.

A) Propionyl-CoA
B) Acetoacetyl-CoA
C) Malonyl-CoA
D) Butyryl-CoA
E) None of the above is correct

Question 17

All of the following are enzymatic activities found in fatty acid synthase except

A) $\beta$ -Ketoacyl-ACP reductase
B) Malonyl/acetyl transferase
C) Thioesterase
D) Lipoxygenase
E) $\beta$ -Hydroxyacyl-ACP dehydratase

Question 18

Desaturation of fatty acids involves all of the following except

A) Oxygen
B) NADH
C) Cytochrome b₅
D) Cytochrome b₅ reductase
E) None of the above is correct

Question 19

Which of the following types of fatty acid oxidation produces a dicarboxylic acid?

A) Alpha
B) Beta
C) Delta
D) Omega
E) A and D

Question 20

The conversion of acetyl-CoA to malonyl-CoA is inhibited by ________.

A) Glucagon
B) Epinephrine
C) Palmitoyl-CoA
D) All of the above are correct
E) None of the above is correct

Question 21

The conversion of acyl-CoA to acylcarnitine is inhibited by __________.

A) Malonyl-CoA
B) Citrate
C) Acetyl-CoA
D) Insulin
E) Both A and B are correct

Question 22

In conjugation reactions

A) An insoluble molecule is converted to a precipitate
B) A soluble molecule is excreted
C) An insoluble molecule is made soluble by conversion to a derivative with a water soluble functional group
D) Both A and B are correct
E) None of the above is correct.

Question 23

Depending on an animal's metabolic needs, fatty acids may be converted to triacylglycerols, energy, or __________.

A) Converted to glycerol
B) Stored as terpenes
C) Used in membrane synthesis
D) Both B and C are correct
E) Stored as fatty acids

Question 24

Membrane remodeling

A) Requires phospholipases
B) Requires acyl transferases
C) Occurs only when cells are under stress
D) Both A and B are correct
E) All of the above are correct

Question 25

The conversion of phosphatidylethanolamine to phosphatidylcholine requires ______

A) SAH
B) SAM
C) Acyl carrier protein
D) Serine
E) Base exchange enzyme

Question 26

The sulfatides are synthesized when ________ reacts with
3-phosphoadenosine-5'-phosphosulfate.

A) Phosphatidylceramide
B) Phosphatidylcholine
C) Galactocerebroside
D) Sphingomyelin
E) UDP-glucose

Question 27

__________ is the rate-limiting enzyme in cholesterol synthesis.

A) HMG-CoA reductase phosphatase
B) HMG-CoA reductase kinase
C) Mevalonate kinase
D) Phosphomevalonate kinase
E) None of the above is correct

Question 28

The conversion of squalene to cholesterol requires ________.

A) Oxygen
B) Isopentenyl pyrophosphate
C) NADPH
D) Both A and B are correct
E) Both A and C are correct

Question 29

Cholesterol is a precursor of _________.

A) Aldosterone
B) Cortisol
C) Testosterone
D) Estrogen
E) All of the above are correct

Question 30

Most bile acids are conjugated with ________.

A) Glycine
B) Glucuronate
C) Taurine
D) Both A and B are correct
E) Both A and C are correct

Question 31

Which of the following tissues cannot use fatty acids as a fuel?

A) Brain
B) Muscle
C) Heart
D) Liver
E) All tissues use fatty acids

Question 32

Lipolysis is used to

A) Degrade triacylglycerols
B) Prepare triacylglycerols for excretion
C) Remove lipid from membrane
D) Cleave fatty acids into two carbon units
E) Convert fatty acids to glucose

Question 33

Oxidation of the carbon farthest from the carbonyl group of a fatty acid is called

A) $\alpha$ oxidation
B) $\beta$ -oxidation
C) $\omega$ -oxidation
D) The reaction does not occur
E) Either A or B are correct depending on the point of reference

Question 34

In the process of thiolytic cleavage the following occurs:

A) A cis double bond is produced
B) A trans double bond is produced
C) An acetyl CoA molecule is released when the bond between C $\alpha$ and C $\beta$ of an acyl-CoA is broken
D) A fatty acid reacts with CoA to produce an acetyl-CoA
E) Hydrogen sulfide is used to cleave the carbon-carbon double bond

Question 35

How many FADH₂ molecules would be produced in the oxidation of palmitic acid?

A) 1
B) 3
C) 5
D) 7
E) 9

Question 36

The rate limiting step in fatty acid synthesis is

A) Acetyl-CoA carboxylation
B) Reduction of a cis double bond
C) Conversion of the trans double bond to a cis double bond
D) Reduction of the ketoester to the hydroxyl ester
E) Desaturation of the fatty acid to form trans double bonds

Question 37

Which of the following lipids have signaling functions?

A) Triacylglycerols
B) Steroids
C) Bile salts
D) Prostaglandins
E) $\alpha$ -tocopherol

Question 38

What form of oxidation is characteristic of branched chain fatty acids

A) $\alpha$ -oxidation
B) $\beta$ -oxidation
C) $\gamma$ -oxidation
D) $\delta$ -oxidation
E) $\omega$ -oxidation

Question 39

The metabolism of fatty acids is regulated in the short term by allosteric modulators, covalent modification and _________.

A) Fluctuating nutrient availability
B) Energy demands
C) Changes in gene expression
D) Hormones
E) A, B, and C are all correct

Question 40

The most important mechanism for degrading and eliminating cholesterol is the synthesis of

A) Fatty acids
B) Bile acids
C) Squalene
D) Taurine
E) Isoprene

Question 41

The absorption of triglycerides and other lipid nutrients and their distribution to body tissues is referred to as the

A) Endogenous pathway
B) Exogenous pathway
C) Apolipoprotein pathway
D) Chylomicron distribution pathway
E) Triacylglycerol absorption pathway

Question 42

The pathway in which lipoproteins are transported from the liver to cells is referred to

A) Endogenous pathway
B) Exogenous pathway
C) Apolipoprotein pathway
D) Chylomicron distribution pathway
E) Triacylglycerol absorption pathway

Question 43

Which of the following is not a function of lipids

A) Energy storage
B) Components of biological membranes
C) Insulation
D) Source of acetyl-CoA
E) All of the above are functions of lipids

Question 44

The triacylglycerol cycle is

A) A mechanism for releasing amino acids to the liver
B) A mechanism that regulates the level of fatty acids that are
Available for energy generation.
C) A mechanism that hydrolyses triacylglycerol
D) Converts fatty acids to triacylglycerol
E) B, C, and D

Question 45

The principal means of producing glycerol in the body

A) The triacylglycerol cycle
B) Glyceroneogenesis
C) Gluconeogenesis
D) Lipolysis
E) Liponeogenesis

Question 46

The recycling rate of triacylglycerols to fatty acids is inhibited by

A) Epinephrine
B) Norepinephrine
C) Insulin
D) Lipase
E) A and B

Question 47

What is an enterocyte? What is its function?

Question 48

Define ketogenesis.

Question 49

Define ketosis.

Question 50

What are the differences between $\beta$ -oxidation in mitochondria and peroxisomes?

Question 51

List three differences between fatty acid synthesis and $\beta$ -oxidation

Question 52

Explain how hormones act to modify the metabolism of fatty acids in both the short and long term. Give examples.

Question 53

Define the term thiolytic cleavage. In what biochemical process does it occur?

Question 54

How do cells adjust the fluidity of their membranes?

Question 55

Describe the difference between LDLs and IDLs.

Question 56

$\beta$ -Oxidation of naturally occurring monounsaturated fatty acids requires an additional enzyme. What is this enzyme and how does it accomplish its task?

Question 57

What is the function of a glucocorticoid?

Question 58

What is the function of a Phase I reaction?

Question 59

How would you describe the three phases of biotransformation?

Question 60

What is the function of ACP?

Question 61

What is the function of conjugation reactions in the biotransformation process?

Question 62

Under severe starvation conditions people develop "acetone breath". Explain.

Question 63

Describe the role of insulin in lipid metabolism.

Question 64

Describe the possible effects of low levels of carnitine on a person's metabolism.

Question 65

When the production of acetyl-CoA exceeds the body's capacity to oxidize it, acetoacetate, $\beta$ -hyroxybutyrate and acetone accumulate. When generated in large amounts, these substances can exceed the blood's buffering capacity. As the blood pH falls, the ability of red blood cells to carry oxygen is affected. Subsequently, the brain can be starved of oxygen and a fatal coma can result. Explain how severe dieting can produce this condition.

Question 66

There is an unusually high concentration of phosphatidylcholine on the lumenal side of the ER. What structural feature of phosphatidylcholine is responsible? Explain how this structural feature produces this effect.

Question 67

During periods of stress or fasting, fatty acids are released by adipocytes. Explain.

Question 68

Pharmaceuticals in a class called statins inhibit the enzyme HMG-CoA reductase. What is the primary effect of this drug on patients?

Question 69

Describe the role of the three proteins that facilitate the movement of phospholipid across a membrane.

Question 70

Provide an explanation for the fact that most fatty acids are 16 to 18 carbons long.

Question 71

How are lipid molecules such as estrogen and $\beta$ -carotene related to each other?What biosynthesis reaction do these specific molecules have in common?

Question 72

Provide an explanation for the intracellular separation of fatty acid metabolic processes

Question 73

Butyric acid, a simple four-carbon fatty acid, is oxidized by $\beta$ -oxidation. Calculate the number of FADH₂ and NADH molecules that are produced in this reaction. How many acetyl-CoA molecules are produced?

Question 74

The adaptation of desert animals to their environment requires water conservation mechanisms. A number of these organisms conserve water so successfully that they never actually drink it. They depend instead on water generated during metabolism. Determine how much water can be obtained by the oxidation of one mole of palmitic acid.

Question 75

Compare the energy content of a stearic acid molecule with that of glucose.