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Biochemistry Exam 3 > Chapter 29: Lipid Synthesis: Storage Lipids, Phospholipids, and Cholesterol > Flashcards

Chapter 29: Lipid Synthesis: Storage Lipids, Phospholipids, and Cholesterol Flashcards

0
Q

What is the storage form of FAs?

A

Triacylglycerol

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1
Q

Lipids are made from _____ or from their breakdown products.

A

Fatty acids

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2
Q

Phospholipids and sphingolipids make up…

A

Membrane lipids

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3
Q

Membrane components and precursor to steroid hormones

A

Cholesterol

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4
Q

What is the precursor of storage lipids?

A

Phosphatidate

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5
Q

Phosphatidate (diacylglycerol 3-phosphate) is formed by the addition of _____ to _____.

A

Two fatty acids to glycerol 3-phosphate

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6
Q

Glycerol 3-phosphate –> _____ –> _____.

A

–> Lysophosphatidate –> Phosphatidate

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7
Q

What is bound to ER and synthesizes triacylglycerol from phosphatidate and acyl CoA in liver?

A

Triacylglycerol synthase

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8
Q

TAG is transported to _____ or _____

A

Muscle (fuel) or Adipose tissue (storage)

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9
Q

Phosphatidate –> DAG –>

A

TAG

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10
Q

Phosphatidate is the precursor to make…

A

Triacylglycerols (TAG)

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11
Q

Phospholipids are generated from _____ and _____ in the ER.

A

Phosphatidate and Alcohol

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12
Q

Phospholipid synthesis requires the activation of _____ to provide the needed energy

A

Either alcohol or phosphatidate

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13
Q

DAG is activated by forming _____.

A

CDP-diacylglycerol

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14
Q

In other cases, the alcohol is activated by _____ and subsequent _____ to form _____.

A

Activated by phosphorylation and subsequent reaction with CTP to form CDP-alcohol

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15
Q

The activated alcohol in phospholipid synthesis reacts with _____ to form the phospholipid.

A

Diacylglycerol

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16
Q

Sphingolipids are synthesized from _____.

A

Ceramide

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17
Q

Sphingolipids: Membrane lipids found in all eukaryotic cells, have a _____ instead of a glycerol bakcbone.

A

Sphingosine backbone

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18
Q

Sphingolipids are synthesized from _____ and _____.

A

Palmitoyl CoA and serine

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19
Q

What is the initial product of sphingolipid sythesis?

A

Ceramide

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20
Q

The _____ of ceramide is substituted to form other sphingolipids.

A

Terminal hydroxyl group

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21
Q

_____ is found in the extracellular fluid in lungs and prevent lung collapse after exhaling.

A

Dipalmitoyl phosphatidylcholine

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22
Q

Describe Respiratory Disease Syndrome

A

Failure to synthesize sufficient dipalmitoyl phosphatidylcholine, leading to collapse of the lung

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23
Q

Describe Tay-Sachs Disease.

A
  • Inability to degrade ganglioside (phospholipids) due to lack of beta-N-acetylhexosaminidase in lysosomes
  • Neurons become swollen with lipid-filled lysosomes, which leads to lack of psychomotor skills and blindness
  • Tay-Sachs disease results in death by age 3
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24
Q

What is a key regulatory enzyme in lipid metabolism?

A

Phosphatidic Acid Phosphatase

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25
Q

What catalyzes the conversion of phosphatidate to diacylglycerol?

A

Phosphatidic acid phosphatase (regulates lipid metabolism)

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26
Q

Different lipids are synthesized depending on whether the phosphatase is _____ or _____.

A

Active or Inactive

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27
Q

Loss of phosphatase activity in mice results in loss of _____ and the development of _____.

A

Loss of body fat Development of insulin resistance

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28
Q

Excess phosphatase activity results in _____.

A

Obesity

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29
Q

No cholesterol = ?

A

No membrane function

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30
Q

Cholesterol is synthesized from _____.

A

Acetyl Coenzyme A

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31
Q

_____ is the primary site of cholesterol synthesis.

A

Liver

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32
Q

All 27 carbons of cholesterol are derived from _____.

A

Acetyl CoA

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33
Q

Cholesterol is synthesized from acetyl CoA to _____ to _____.

A

Mevalonate to isopentenyl pyrophosphate

34
Q

6 molecules of isopentenyl pyrophosphate are condensed into _____.

A

Squalene

35
Q

Squalene is cyclized into…

A

Cholesterol

36
Q

What is the rate-limiting step of cholesterol synthesis?

A

Mevalonate formation

37
Q

_____ initiates the synthesis of cholesterol

A

Formation of mevalonate

38
Q

First step in the synthesis of cholesterol is the formation of mevalonate by…

A

HMG-CoA Reductase

39
Q

HMG-CoA Reductase catalyzes the _____ and is the major _____ for cholesterol synthesis.

A

Catalyzes the committed step and is the major control site

40
Q

HMG-CoA Reductase is an _____ in the _____.

A

Integral membrane protein in the ER

41
Q

In other words, mevalonate determines…

A

How much cholesterol is synthesized by the cell

42
Q

HMG-CoA reductase is controlled by four different mechanisms in response to cellular cholesterol levels:

A
  1. Regulation of transcription
  2. Covalent modification
  3. Regulation of translation
  4. Control of degradation
43
Q

HMG-CoA Reductase synthesis rate is controlled by…

A

SREBP

44
Q

HMG-CoA Reductase: When cholesterol levels increase,

A

Degradation of the reductase occurs

45
Q

HMG-CoA Reductase: Phosphorylation will

A

Inactivate the enzyme

46
Q

Cholesterol and triacylglycerols are NOT _____ and transported in the blood in form of _____ particles.

A

NOT water-soluble and transported in the form of lipoprotein particles

47
Q

Lipoprotein particles consist of a _____ component and various _____.

A

Protein component and various lipids

48
Q

The protein(s) serve to _____ the lipids and to _____ the particles to specific targets.

A

Serve to solubilize the lipids and to direct the particles to specific targets (specific tissues)

49
Q

Lipoprotein particles are classified according to _____.

A

Increasing density

50
Q

Proteins are _____ than lipids.

A

Denser

The higher density lipoproteins have MORE protein

51
Q

VLDL is what % lipid?

A

98%

52
Q

Cholesterol is carried by _____.

A

LDLs.

54
Q

High levels of HDL…

A

Decrease the risk for heart disease

55
Q

LDL _____ bloodstream; HDL _____ bloodstream.

A

LDL brings chol. to bloodstream; HDL removes chol. from bloodstream

56
Q

The major carrier of cholesterol in the blood

A

Low-density lipoprotein (LDL)

57
Q

Carries cholesterol released into the blood back to the liver - reverse cholesterol transport

A

High-density lipoprotein (HDL)

58
Q

Which type is known as the ‘bad’ cholesterol?

A

LDL - can cause heart attacks

59
Q

LDL plays a central role in…

A

Cholesterol Metabolism

60
Q

LDLs deliver cholesterol to peripheral tissues and cholesterol enters the cell by _____.

A

Receptor-mediated endocytosis

61
Q

What is the genetic disease that results from the absence of functional LDL receptor?

A

Familial hypercholesterolemia

  • High levels of cholesterol and LDL in plasma
  • Excess LDL contribute to development of heart attacks
62
Q

What is the goal to treat high blood cholesterol?

A
  • Goal is to increase # of LDL-R to more effectively remove cholesterol
63
Q

How do you treat high blood cholesterol? 2 Treatments

A
  1. Decrease new cholesterol synthesis by inhibition of HMG-CoA reductase by a class of drugs called statins.
  2. Block the uptake of dietary cholesterol
    • Blocked by ingesting a resin that binds to the bile salts
64
Q

HDL protects against…

A

Atherosclerosis

65
Q

HDL is considered the ‘good’ cholesterol because it can _____ by retrieving cholesterol from other tissues to the liver for excretion.

A

Prevent heart attacks

66
Q

What is the precursor to steroid hormones, vitamin D and bile salts?

A

Cholesterol

67
Q

Steroid hormones are crucial _____.

A

Signaling molecules

68
Q

All five major classes of steroid hormones are derived from _____.

A

Cholesterol

69
Q

Vitamin D is derived from cholesterol by _____.

A

Energy of sunlight

70
Q

Regulation of calcium and phosphate metabolism

A

Vitamin D

71
Q

Active form of vitamin D formed from cholesterol

A

Calcitriol

72
Q

Deficiency of vitamin D results in…

A
  • Rickets: inadequate calcification of cartilage and bone
73
Q

In adults, vitamin D deficiency results in…

A

Osteomalacia, a condition characterized by soft and weak bones

74
Q

T or F: HMG CoA reductase catalyzes the first committed step of cholesterol synthesis.

A

True

75
Q

T or F: HMG CoA reductase can be regulated by phosphorylation.

A

True

76
Q

T or F: The absence of sterols results in an increase in HMG CoA reductase degradation

A

False

77
Q

T or F: SREBP is involved in transcriptional regulation of the HMG CoA reductase gene

A

True

78
Q

T or F: Statins are competitive inhibitors of HMG CoA reductase.

A

True

79
Q

Lipids in the intestine are coated with _____ and digested by _____?

A
  • Coated with bile salts
  • Digested by pancreatic lipases
80
Q

Which is NOT a method for regulation of HMG CoA reductase?

  • Inactivation due to phosphorylation by AMP-dependent kinase
  • Alteration in rate of translation of reductase mRNA by dietary cholesterol
  • Regulation of rate of synthesis of reductase mRNA by SREBP
  • Proteolytic degradation of reductase controlled by cholesterol levels
  • Transportation of reductase to the mitochondria controlled by cholesterol levels
A

Transportation of reductase to the mitochondria controlled by cholesterol levels

81
Q

Cholesterol is used in formation of:

  • Bile salts
  • Testosterone and other steroid hormones
  • Cholesterol esters
  • Vitamin D
A

All are correct

82
Q

If levels of cholesterol are low:

  • Proteolysis of HMG CoA reductase is increased
  • HMG CoA reductase is phosphorylated by AMP-activated protein kinase
  • HMG CoA reductase is translocated to the nucleus
  • SREBP is cleaved by a protease, allowing the DNA binding domain to increase transcription of the HMG CoA reductase gene
  • HMG CoA reductase expression is not altered in any way
A

SREBP is cleaved by a protease, allowing the DNA binding domain to increase transcription of the HMG CoA reductase gene

83
Q

Lipoproteins:

  • Are used primarily to transport amino acids throughout the body
  • Contain hydrophobic cores with triacylglycerols and cholesterol esters
  • Have hydrophobic surfaces with charged carbohydrates
  • Contain only cholesterol as a lipid component
  • Function only in the liver
A

Contain hydrophobic cores with triacylglycerols and cholesterol esters

Biochemistry Exam 3 (10 decks)

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