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Biochem Loyola > Triacylglycerides Lecture > Flashcards

Triacylglycerides Lecture Flashcards

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1
Q

What is the key control enzyme in fatty acid biosynthesis?

A

Acetyl-CoA carboxylase

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2
Q

Is HMG-CoA reductase activated in the fed or fasted state?

A

Fed

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3
Q

What reaction is facilitated by HMG-CoA reductase?

A

Acetyl-CoA to cholesterol

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4
Q

What hormone mobilizes fatty acyl-CoA through carnitine palmitoyltransferase I to turn into acetyl Co-A

A

Epinephrine

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5
Q

Where can HMG-CoA synthase be found in the cell?

A

Only in the mitochondria

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6
Q

What reaction does HMG-CoA synthase facilitate?

A

Acetyl CoA to Ketone Bodies

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7
Q

What reaction does 7-alpha-hydroxylase facilitate?

A

Cholesterol to bile acids

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8
Q

What reaction does ACAT catalyze?

A

Cholesterol to cholesterol ester

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9
Q

Where can Succinyl-CoA transferase not be found?

A

Liver

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10
Q

What reaction does succinyl-CoA transferase facilitate?

A

Ketone bodies to acetyl-CoA

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11
Q

What reaction does Acetyl-CoA carboxylase facilitate?

A

Acetyl-CoA to fatty acyl CoA

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12
Q

What does fatty acyl-CoA convert to in the fed state?

A

triacylglycerols

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13
Q

What is the effect of insulin on acetyl-CoA carboxylase

A

Promotes conversion of acetyl CoA to fatty acyl-CoA

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14
Q

In the fed state, acetyl-CoA will be converted to cholesterol - true or false?

A

True

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15
Q

In the fasting state, acetyl-CoA will be converted to cholesterol - true or false?

A

False, it will be converted to ketone bodies

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16
Q

How do you get TAGs in the bloodstream through the liver?

A

Glucose and other fuels –> Acetyl CoA –> FA –> TAG –> VLDL

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17
Q

How do you get dietary TAGs into the bloodstream?

A

Dietary TAGs in the small intestine will enter chylomicrons which will enter the bloodstream

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18
Q

What enters the muscles during the fed state?

A

Fatty acids, which are oxidized for energy

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19
Q

What enters the adipose tissue during the fed state?

A

Fatty acids, which are then converted to TAGs

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20
Q

How are fatty acids transported during the fed state?

A

As part of TAGs on lipoproteins

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21
Q

How are fatty acids transported during the fasted state?

A

Bound to albumin

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22
Q

What pathway does glycerol go through during the fasted state?

A

gluconeogenesis

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23
Q

What is the fate of ketone bodies during the fasted state?

A

They will enter the CNS and muscle to be oxidized for energy

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24
Q

What is the fate of fatty acids in the liver during the fasted state?

A

FA –> AcCoA –> ketone bodies –ketone bodies in blood stream–> ketone bodies in muscle, other tissues, CNS –> ketone bodies oxidized for energy

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25
What is the reaction to go from acetyl CoA to palmitate?
AcCoA + 7 malonyl-CoA + 14 NADPH + 14H+ --> Palmitate + 7 CO2 + 14 NADP + 8 CoA + 6H20
26
What is the rate limiting enzyme of DeNovo biosynthesis of fatty acids?
Acetyl-CoA Carboxylase
27
What reaction does acetyl-CoA carboxylase facilitate in DeNovo FA biosynthesis
1+7 Acetyl-CoA + 7CO2 --> 7 Malonyl-CoA
28
What enzyme facilitates the decarboxylation and reduction steps of de novo fatty acid synthesis
Fatty acid synthase
29
What are the 5 necessary components of fatty acid biosynthesis
1. Acetyl groups 2. AcCoA carboxylase 3. Biotin 4. Fatty acid synthase complex 5. NADPH
30
What transports acetyl groups for fatty acid biosynthesis from mitochondria to the cytoplasm?
Citrate
31
What is the purpose of biotin in the synthesis of FAs
carrier molecule of activated CO2
32
All carbons are derived (ultimately) from _________
Acetyl CoA
33
Where do most acetyl CoAs come from?
Carbohydrate metabolism
34
What are the 3 functions of citrate in regards to FA metabolism?
1. stimulates FA biosynthesis 2. transports acetyl groups from mitochondria 3. allosterically activates Acetyl CoA carboxylase
35
Citrate is the carrier of ________ from the mitochondria to the cytoplasm
Acetyl groups
36
How does Acetyl CoA catalyze the formation of malonyl CoA
It adds CO2
37
What are the effects of citrate on acetyl CoA carboxylase
activation
38
What are the effects of insulin on acetyl-CoA carboxylase?
activation
39
What are the effects of biotin on acetyl-CoA carboxylase?
activation; serves as a cofactor carrying activated CO2
40
What are the effects of palmitoyl CoA on acetyl-CoA carboxylase
inhibition
41
What are the effects of glucagon on acetyl-CoA carboxylase?
inhibition
42
What are the effects of glucagon on acetyl-CoA carboxylase?
inhibition
43
Acetyl-CoA carboxylase catalyzes a reversible reaction - True or false?
False, the reaction is irreversible.
44
What are the products and reactants in the reaction catalyzed by Acetyl-CoA carboxylase?
Reactants: Acetyl CoA, HCO3-, ATP Products: Malonyl CoA, H20, ADP, Pi
45
what enzyme produces malonyl CoA?
The reaction catalyzed by acetyl-CoA carboxylase
46
What is the only physiological inhibitor of the rate limiting enzyme in fatty acid oxidation?
malonyl CoA
47
Malonyl CoA is the key regulator of _________ and _________
FA oxidation; ketone body formation
48
What is a short term allosteric activator of acetyl-coA carboxylase?
Citrate
49
What is a short term allosteric inhibitor of acetyl-CoA carboxylase?
palmitoyl-CoA (long chain fatty acyl CoA, C16-C18) and AMP (via AMPK)
50
What is a short-term hormonal activator of acetyl-CoA carboxylase?
insulin (dephosphorylation)
51
What is a short-term hormonal inhibitor of acetyl-CoA carboxylase?
Glucagon, epinephrine (promote covalent modification/phosphorylation)
52
What are the long term regulations that increase Acetyl-CoA carboxylase synthesis?
High carbohydrate diet, insulin, thyroid hormone, fat free diet
53
What are the long-term regulations that decrease Acetyl-CoA carboxylase synthesis?
High fat diet (via low insulin, high glucagon), fasting, glucagon
54
The Fatty Acid Synthase (FAS) complex catalyzes the formation of ___________ from ___________ and ___________.
fatty acids (palmitate); 1 acetyl-CoA; 7 malonyl-CoA
55
How many reaction cycles does FAS complex catalyze?
7
56
What is the first major step in forming a C16 compound?
Condensation
57
What step does acetyltransferase perform?
Acetyl CoA --> butyryl acetyl carrier protein + CoA
58
What step does malonyltransferase perform?
malonyl CoA --> Malonate + CoA
59
What electron carrier is used in the reduction steps?
NADPH
60
What is the starting molecule in fatty acid elongation?
butyryl CoA
61
Where in the cell does acetyl CoA carboxylase work?
Cytoplasm
62
What are the 6 enzymes of the fatty acid synthase complex
1. acetyl transacylase 2. malonyl transacylase 3. ketoacyl carrier protein synthase (acyl-malonyl-ACP-reductase) 4. Ketoacyl ACP reductase 5. 3-hydroxyacyl ACP dehydratase 6. enoyl ACP reductase
63
What is the full reaction catalyzed by acetyl-CoA carboxylase?
Acetyl-CoA + HCO3- + ATP --> Malonyl CoA + ADP + Pi + H+
64
What is the full reaction catalyzed by acetyl transacylase?
Acetyl-CoA + ACP --> acetyl-ACP + CoA
65
What is the full reaction catalyzed by malonyl transacylase?
Malonyl-CoA + ACP --> Malonyl-ACP + CoA
66
What is the full reaction catalyzed by ketoacyl-carrier-protein synthase (Acyl-Malonyl-ACP-reductase)?
Acetyl-ACP + malonyl-ACP --> acetoacetyl-ACP + ACP + CO2
67
What is the full reaction catalyzed by ketoacyl-ACP reductase?
acetoacetyl-ACP + NADPH + H+ --> D-3-hydroxybutyryl-ACP + NADP+
68
What is the full reaction catalyzed by 3-hydroxyacyl-ACP dehydratase?
D-3-hydroxybutyryl-ACP --> Crotonyl-ACP + H20
69
What is the full reaction catalyzed by Enoyl-ACP Reductase?
crotonyl-ACP + NADPH + H+ --> butyryl-ACP + NADP+
70
What is the short term allosteric activator of the FAS complex?
Fructose-1,6-bisphosphate
71
When would the allosteric activator of the FAS complex be expressed most?
When blood glucose concentrations are high
72
What are 2 ways to increase enzyme synthesis to increase FAS complex function?
1. high carbohydrate diet via insulin | 2. Fat free diet
73
What are 3 ways to decrease enzyme synthesis to decrease FAS complex function?
1. Glucagon 2. High fat diet via low insulin and high glucagon 3. Fasting
74
Why would fasting decrease FAS complex function?
Fasting mobilizes fatty acids
75
What do you get if you elongate palmitate?
Stearate
76
What do you get if you desaturate palmitate?
Palmitoleate
77
What do you get if you desaturate stearate?
Oleate
78
What do you get if you desaturate oleate?
Linoleate (18:2)
79
What do you get if you desaturate linoleate?
Linolenate
80
What do you get if you elongate and desaturate linolenate?
Arachidonate
81
What 3 main things are fatty acids ultimately esterified to?
1. Triacylglycerols 2. Phospholipids 3. Cholesterols
82
What are the required cofactors for the reaction palmitate --> palmitoyl-CoA?
ATP + CoA --> AMP + PPi
83
What does esterification of palmitoyl-CoA result in?
1. acylglycerols - TAGs | 2. Cholesterol Esters
84
What does chain elongation/desaturation of palmitoyl-CoA result in?
Acyl-CoA
85
What percent of fatty acids mobilized in the fasting state are redeposited in fatty tissue?
60%
86
What is endogenous synthesis of TAGs primarily regulated by?
substrate availability
87
PPARs (peroxisome proliferator-activated receptors) promote or inhibit TAG deposition?
Promote
88
TAGs synthesized in the liver are packaged into _____
VLDLs
89
Glycerol-3-phosphate is a precursor for _____
TAGs
90
Dietary TAGs and synthesized TAGs are packaged into __________ for transport in the circulation
Lipoproteins
91
Dietary TAGs are incorporated into __________
Chylomicrons

Biochem Loyola (14 decks)

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