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Biochemistry Exam III material > Lipid Metabolism I > Flashcards

Lipid Metabolism I Flashcards

1
Q

Fatty acids are stored as

A

Triacylglycerols (TAGS) in adipose Tissue

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2
Q

Triacylgycerols (TAG) are highly concentrated stores of metabolic energy because they are

A

reduced and anhydrous

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3
Q

TAGs are uncharged _____ of fatty acids with glycerol

A

esters

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4
Q

TAGs are the building blocks for

A

phospholipids and glycolipids

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5
Q

TAGs present in diet must be

A

broken down to fatty acids for absorption

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6
Q

_____ fuel long migration flights of birds, such as the American golden plover

A

Triacyglycerols

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7
Q

Intestinal enzymes called ______, secreted by the _____, degrade triaglycerols to free fatty acids and monoacylglycerol

A

Lipases, pancreas

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8
Q

____ and _____ present in tongue and stomach, respectively, digest short and medium chain Fatty acids in TAGs (

A

Lingual, gastric lipase

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9
Q

The breakdown of lipids depends on

A

length of fatty acids in the TAG

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10
Q

Because lipids are not water soluble what must be done before lipase can digest the fatty acid

A

-Bile salts emulsify the lipids in the small intestine
- This allows the ester bonds of each lipid to orient toward the bile salt and be more open to lipase digestion
(note that colipase must bind the lipase to the particle to permit lipid degradation)

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11
Q

What is emulsification

A

suspension into small particles in the aqueous environment

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12
Q

Biles salts are ______ (have hydrophobic and hydrophilic components)

A

amphipathic

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13
Q

Contraction of _____ to release bile salts and other pancreatic enzymes is stimulated by the gut hormone cholecystokinin

A

gallbladder

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14
Q

Contraction of gallbladder to release bile salts and other pancreatic enzymes is stimulated by the gut hormone

A

Cholecystokinin

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15
Q

Bile salts are synthesized from _____ in the ____-

A

cholesterol in the liver

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16
Q

Emulsification of lipids greatly

A

increases the surface area of fats

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17
Q

_____ is released in response to acidic material

A

secretin

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18
Q

What is steatorrhea

A

production of bile salts is inadequate due to liver disease, large amount of fats (as much as 30g a day) are excreted in feces

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19
Q

The release of secretin stimulates the release of

A

bicarbonate which increases the pH to 6, optimal for intestinal enzymes

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20
Q

What is the optimal pH for intestinal enzymes

A

6

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21
Q

Pancreatic lipase digests all lengths of FA. forms ____ and _____

A

Free fatty acids and 2-monoacylglycerol (2-MAG)

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22
Q

The pancreas produces ____ which removes FA form cholesterol esters

A

esterase

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23
Q

Esterase removes FA from

A

cholesterol esters

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24
Q

Pancreas produces _____ which removes FA from phospholipids

A

phospholipase A2

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25
Q

Phospholipase A2 removes FA form

A

phospholipids

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26
Q

The use of fatty acids as fuel requires how many staging processes and what are they

A

3
First must be mobilized- TAGs are degraded to fatty acids and glycerol, which are released form the adipose tissue and transported to the energy-requiring tissues
second must be activated an transported into mitochondria for degradation
third- the fatty acids are broken down in a step-by-step fashion into acetyl CoA, which is then processed in the TCA

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27
Q

Short and medium chain FA (C4-C12) are absorbed into

A

intestinal epithelial cells

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28
Q

Short and medium chain FA (C4-C12) that are absorbed into intestinal epithelial cells enter straight into _____ and are transported into the ____ bound to serum ____

A

Portal blood, Liver, Albumin

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29
Q

Long chain FAs (13C-21C) and 2-MAGs are packed into _____ and emulsified by

A

micelles, bile salts before being absorbed into the walls of the small intestine

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30
Q

Lipids such as cholesterol, lyso PLs and fat soluble vitamins follow routes similar to

A

long chain FAs and 2-MAGs

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31
Q

Lipids are absorbed across ____, bile salts are left in the ____

A

microvilli, gut

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32
Q

once FA and MAGs are inside the intestinal cells they are condensed to form _____ (in smooth ER)

A

TAG

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33
Q

Once reassembled into TAG in the smooth ER of the intestinal cells lipids are packaged into

A

Chylomicrons

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34
Q

Chylomicrons are

A

lipoprotein transport particles: that contain Proteins (Apoprotein B48) and TAGs, fat-soluble vitamins, phospholipids, and cholesterol.

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35
Q

What is the main protein component of chylomicrons

A

Apoliprotein B-48

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36
Q

Protein constituents of lipoprotein particles are called

A

apolipoproteins

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37
Q

Chylomicrons are released into the

A

lymph system and then into the blood

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38
Q

in the resynthesis of TAGs in intestinal cells the first step is

A

The activation of Fatty acids

FA + ATP ——> FA-AMP + (CoASH) —–> FACoA + AMP

  • in order to make TAG you must activate 2FAs
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39
Q

once the fatty acids are activated in the intestinal cells you can now undergo TAG synthesis and Nascent Chylomicron production. What are the steps?

A

2-Monoacylglycerol + FACoA ——> Diacylglycerol + FACoA ——> TAG + Apoprotein B48 + other lipids —–> Nascent chylomicrons

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40
Q

dietary FA are delivered to tissues in the form of

A

TAGs (they arrive at the tissues in the form of chylomicrons. They bind to membrane bound lipase and are degraded into free FAs and 2-MAG to enter cell)

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41
Q

Nascent chylomicrons are secreted by intestinal epithelial cells by

A

exocytosis

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42
Q

Nascent chylomicrons are secreted into the

A

lymphatic system

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43
Q

Nascent chylomicrons enter blood from lymphatic system via

A

thoracic duct

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44
Q

Nascent chylomicrons accept proteins from ____ within lymph and blood, which converts them into mature chylomicrons

A

HDL (high-density lipoprotein)

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45
Q

Nascent chylomicrons accept proteins from HDL (high-density lipoprotein) within lymph and blood, which converts them into

A

Mature chylomicrons

46
Q

ApoE and ApoCII are what

A

very important lipoproteins

47
Q

ApoE

A

is a very important lipoprotein that is recognized by receptors on surface of liver cells allowing for endocytosis (This allows for the remnants of chylomicrons to be taken up by liver and lysosomal enzymes within the hepatocyte digest the remnants, releasing the products into the cytosol)

48
Q

ApoCII

A

Very important Lipoprotein that activates lipoprotein lipase present on capillary endothelial cells in muscle and adipose tissue which digests chylomicrons (this allows for the FA and 2-MAG to enter the cell)

49
Q

Lipoprotein lipase is activated by

50
Q

Chylomicrons can not go through

A

the plasma membrane

51
Q

Lipoproteinlipae is located on

A

the surface of the cells (tissues)

52
Q

TAGs in the chylomicrons are hydrolyzed by

A

lipoprotein on the surface of the cell(which is activated by ApoCII)

53
Q

TAG are synthesized in adipocytes and stored in

A

lipid droplets

54
Q

Utilization of FA as fuel requires how many steps and what are they

A

3,
mobilization
activation
degradation

55
Q

Explain the 3 steps required for utilization of FA as fuel

A
  1. ) mobilization: TAGs in adipose tissue are broken down to FA and glycerol, released and transported to energy requiring tissue
  2. ) activation- the fatty acids must be active and transported into the mitochondria
  3. ) degradation- stepwise breakdown of FA into acetyl CoA which is then processed in TCA cycle
56
Q

Glucagon and epinephrine act on what adipocyte receptor for mobilization of fatty acids

A

7TM receptor

57
Q

The 7TM receptor on adipocytes activates

A

adenylate cyclase

58
Q

Adenylate cyclase

A

enzyme that catalyzes the conversion of ATP not cAMP

59
Q

in mobilization of fatty acids from adipocytes increased levels of cAMP stimulates

A

activation of protein Kinase A

60
Q

What is protein Kinase A role in mobilization of fatty acids from adipocytes

A

phosphorylates 2 key enzymes:

 - Perilipin 
 - Hormone sensitive (HS) lipase
61
Q

What is the role of perilipin activation in mobilization of fatty acids from adipocytes

A

The phosphorylation of perilipin has 2 major effects:

  1. ) restructures fat droplet so that TAGs are more accessible to mobilization
  2. ) Triggers release of a coactivator for adipose TAG lipase (ATGL)
62
Q

once the coactivator binds to ATGL. ATGL

A

initiates the mobilization of TAGs by releasing a FA from TAG, forming diacylglycerol

63
Q

diacylglycerol is covered into a FA and MAG by

A

Hormone-sensitive (HS) lipase

64
Q

what is the role of MAG lipase

A

it produces FA and glycerol from MAG

65
Q

MAG is converted to FA and glycerol by

A

MAG lipase

66
Q

Chanarin-Dorfman syndrome

A

-coactivator for ATGL is missing or defective
- thus fats accumulate throughout the body
other symptoms include: dry skin (icythyosis), enlarged liver, muscle weakness, and mild cognitive disability

67
Q

Epinephrine and glucagon induce

68
Q

Fatty acids are not soluble in aqueous solutions. Thus in order to reach the tissues, the released fatty acids bind to

A

the blood protein albumin

69
Q

Glycerol kinase is only found in

70
Q

What enzyme catalyzes the reaction of glycerol to L-Glycerol 3-phosphate

A

Glycerol kinase (only found in the liver)

71
Q

Glycerol and glycolytic intermediates are readily

A

interconvertible

72
Q

in fatty acid oxidation the activation of the fatty acid occurs in the

A

cytoplasm (ER or outer mitochondrial membrane)

73
Q

fatty acid oxidation occurs in the

A

mitochondrial matrix

74
Q

The activation of a fatty acid is the

A

formation of a thioester linkage to a coenzyme A. using an ATP, coenzyme A, and the enzyme Acyl CoA syntheses (fatty acid thiokinase)

75
Q

The activation of fatty acids occurs in how many steps. Explain

A
  1. first- the fatty acid reacts with ATP to form an acyl adenylate (in this mixed anhydride, the carboxyl group of a fatty acid is bonded to the phosphoric group of AMP)
    second- sulfhydryl group of Coenzyme A attacks the acyl adenylate, which is tightly bound to the enzyme, to form acyl CoA and AMP
76
Q

What makes fatty acid activation in fatty acid oxidation irreversible

A

The pyrophosphate is rapidly hydrolyzed by pyrophosphatase ( The hydrolysis of inorganic pyrophosphate makes biosynthetic reactions irreversible)

77
Q

What traps Fatty acids in the cell and makes it metabolically active

A

fatty acid activation

78
Q

Long chain fatty acids are conjugated to _____ to be carried from the outer mitochondrial membrane into the mitochondrial matrix

79
Q

What catalyzes the reaction of ( Acyl CoA + carnitine —–> Acyl carnitine + HS-CoA)

A

Carnitine acyltransferase I (carnitine palmitoyl transferase I)

80
Q

What catalyzes the reaction of (Acyl Carnitine + CoA ——> carnitine + Acyl CoA)

A

Carnitine acyltransferase II (carnitine palmitoyl transferase II)

81
Q

What special properties does Carnitine have that make it thermodynamically feasible to carry fatty acids into the mitochondrial matrix

A

Zwitterionic nature (has both a positive and negative charge)

82
Q

What shuttles acyl carnitine across the inner mitochondrial membrane

A

translocase

83
Q

Carnitine acyltransferase I is located in

A

the outer mitochondrial membrane

84
Q

Translocase returns carnitine back to the cytoplasmic mitochondrial side in exchange for

A

an incoming acyl carnitine

85
Q

a saturated acyl CoA is degraded by a recurring sequence of ____ reactions. What are they?

A 
4
Oxidation- by FAD
hydration
oxidation by NAD+ 
Thiolysis by Coenzyme A
86
Q

The fatty acid chain is shortened by how many carbons as a result of the 4 degrading reactions

87
Q

what is generated in each round of fatty acid oxidation

A

Acetyl CoA, NADH, FADH2

88
Q

Fatty acid oxidation takes place at the

A

Beta carbon atom (thus the name Beta oxidation pathway)

89
Q

the first reaction in each round of fatty acid degradation is the _____ of acyl CoA by an _________

A

oxidation, Acyl CoA dehydrogenase

90
Q

Products of reaction 1 fatty acid degradation

A

Trans-enoyl CoA

FADH2= 1.5 ATP

91
Q

what is the enzyme in the reaction 2 of fatty acid degradation

A

Enoyl CoA hydratase

92
Q

what is the enzyme in reaction 3 of fatty acid degradation

A

Hydroxy Acyl CoA Dehydrogenase

93
Q

NADH2= how much ATP

A

2.5ATP in electron transport chain

94
Q

What is the enzyme in the 4th reaction of fatty acid degradation

A

Thiolysis/ketothiolase (with a second molecule of Acetyl CoA)

95
Q

The complete oxidation of palmitate yield ____ molecules of ATP

A

106 (note that the gross is 108 but the equivalent of 2 molecules of ATP are consumed in the activation of palmitate)

96
Q

The degradation of palmitoyl CoA (C16-acyl CoA) requires how many reaction cycles

A

7 cycles. In the seventh cycle, the C4-ketoacyl CoA is thiolyzed to two molecules of Acetyl CoA

97
Q

Unsaturated and odd chain FA degradation requires

A

2 additional enzymes

  • Isomerase
  • Reductase
98
Q

_____ and ____ are required for the oxidation of unsaturated fatty acids

A

Isomerase and reductase

99
Q

odd-chain fatty acid yield ______ and ____ in the final thiolysis step

A

Propionyl CoA and Acetyl CoA

100
Q

propionyl CoA is converted into ___ before entering the TCA cycle and the conversion requires

A

Succinyl CoA (conversion requires vitamin B12 (a.k.a. Cobalamin)

101
Q

If OAA is low (due to low carbs) acetyl CoA is

A

not utilized

102
Q

Acetyl CoA combines with OAA to form

103
Q

Acetyl CoA must combine with ____ to enter the TCA cycle

104
Q

in fasting or diabetes, OAA is consumed to form ____by the _____ pathways

A

glucose, gluconeogenic pathway

105
Q

When OAA is low then Acetyl CoA is diverted to the formation of

A

ketone bodies (acetoacetate and D-3-Hydroxybutyrate)

106
Q

Acetoacetate is formed form acetyl CoA in how many steps

107
Q

D-3 hydroxybutyrate is formed by the

A

reduction of acetoacetate in the mitochondrial matrix

108
Q

Because it is a Beta-ketoacid, acetoacetate also undergoes a slow, spontaneous decarboxylation to

A

acetone (this is why the odor of acetone may be detected in the breath of a person who has a high level of acetoacetate in the blood)

109
Q

The major site of production of ketone bodies (acetoacetate and 3-hydroxybutyrate) is in the

110
Q

in prolonged starvation, ____% of the fuel needs of the brain are met by ketone bodies

111
Q

Equation for utilization of Acetoacetate

A

Acetoacetate + Succinyl CoA + CoA transferase —-> Acetoacetyl CoA + CoA + thiolase ——> 2 Acetyl CoA

112
Q

What is DKA

A

The lack or deficiency in insulin leads to glucose not being brought into cells. This means that while free fatty acids are still released there is none or low levels of OAA so Acetyl CoA can’t enter the TCA cycle and is converted to ketone bodies. Ketone bodies are acid and cause pH to drop

Biochemistry Exam III material (13 decks)

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