FA Oxidation and Ketone Bodies Flashcards

1
Q

FA oxidation occurs where?

A

in mitochondria

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2
Q

True or false? Long-chain FAs can’t enter the mitochondria without transport mechanisms. Medium and short-chain FAs can enter by diffusion.

A

true

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3
Q

Medium-chain and short-chain FAs are more water soluble. They are not incorporated into ____. They enter the portal blood and are transported primarily to the ____ where they enter by _____.

A

chylomicrons; liver; diffusion

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4
Q

In the mitochondria, medium and short-chain FAs are activated to ___-___ for beta-oxidation

A

acyl-CoAs

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5
Q

FA binding proteins in the plasma membrane aid in the transport of long-chain FAs from ___ in the blood

A

albumin

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6
Q

Long-chain FAs enter the mitochondria as fatty _____

A

acylcarnitines

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7
Q

A fatty acyl-CoA synthase on the ___ mitochondrial membrane produces acyl-CoAs which enter the mitochondrial ____-membrane space

A

outer; inter

note: CPT I catalyzes this reaction

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8
Q

_____ are transported across the mitochondrial inner membrane in exchange for “free” _____ by cranitittine:acylcarnitine translocase

A

acylcarnitines; carnitine

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9
Q

Inside the mitochondria, the acyl-CoA is “____” by CPT II

A

“regenerated”

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10
Q

Beta-oxidation of long-chain acyl-CoAs is a series of 4 reactions repeated cyclically. Each cycle produces how many acetyl-Coa, FADH2, NADH, and acyl-CoA

A

acetyl-CoA: 1
FADH2: 1
NADH: 1
acyl-CoA: one reduced in length by 2 carbons

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11
Q

Since the 4 reactions of beta-oxidation occur inside the mitochondria, the reduced cofactors are substrates for ____ ____, and the acetyl-CoA is a substrate for the ____ ____

A

oxidative phosphorylation; TCA cycle

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12
Q
Each of the 4 reactions in beta-oxidation is catalyzed by a number of enzymes which have various specificities for chain length. For the following acyl-CoA dehydrogenase, give the light of chain it prefers.
VLCAD
LCAD
MCAD
SCAD
A

VLCAD: prefers C12 to C24
LCAD: C12 to C16
MCAD: C6 and C8
SCAD: C4>C6>C8

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13
Q

The major control of beta-oxidation is exerted at which enzyme?

A

CPT I

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14
Q

CPT I is inhibited by ____-___

A

malonyl-CoA

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15
Q

Malonyl-CoA is the produce of ___-___ carboxylase and is the substrate for FA ____

A

acetyl-CoA; synthesis

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16
Q

Acetyl-CoA carboxylase is stimulated (malonyl-CoA is produced) in what situation?

A

when insulin predominates

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17
Q

Acetyl-CoA carboxylase is inhibitied (malonyl-CoA concentration decreases) in what situation?

A

when glucagon predominates

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18
Q

How do odd-numbered FAs go through Beta-oxidation?

A
  1. at the final stage, one molecule of acetyl-CoA and one molecule of propionyl-CoA are produced
  2. propionyl-CoA is converted to succinyl-CoA
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19
Q

____-___ is a gluconeogenic precursor, and thus the only part of a FA which can result in the net synthesis of glucose

A

Succinyl-CoA

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20
Q

Oxidation of unsaturated FAs have to be handled differently because the double bonds are in the ____ configuration and may involve an ___-numbered carbon

A

cis; odd

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21
Q

Unsaturated FAs are oxidized with help from two enzymes. What are they?

A
  1. enoyl-CoA isomerase

2. 2,4-dienoyl-CoA reductase

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22
Q

Where does oxidation of very long chain FAs (C24-C26) occur?

A

peroxisomes

note: called “modified” beta-oxidation

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23
Q

What are the products of very long chain FA “modified” beta oxidation?

A

acetyl-CoA and a fatty acyl-CoA reduced by 2 carbons

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24
Q

The acyl-CoA oxidation in modified beta oxidation is not linked to cofactor ____

A

reduction; means no energy is provided by this step

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25
The peroxisomal oxidation (modified beta oxidation) proceeds until the acyl-CoA is about ___ carbons long
8
26
The octanoyl-CoA and the acetyl-CoA produced by peroxisomal oxidation are transported to the ____ for further oxidation
mitochondria
27
True or false? animals do not produce branched-chain fatty acids
true
28
The most common long-chain branched FA is a degradation product of ____
chlorophyll
29
long-chain branched FAs are oxidized where?
peroxisomes
30
What are the products of long-chain branched FA oxidation?
1. CO2 2. propionyl-CoA 3. acetyl-CoA
31
In regards to w-oxidation of FAs, the w-carbon is the terminal ___ group of the FA
methyl
32
w-oxidation occurs where? requires what?
occurs in ER | requires cytochrome P450, O2, and NADPH
33
The w-CH3 group is oxidized first to an ____ and then to a ____ ___
alcohol; carboxylic acid note: produces a dicarboxylic acid
34
The w-oxidation pathway is though to function to produce more water-soluble compounds from water insoluble FAs. The products may be oxidized as ___-chain FAs or they can be ___
medium; excreted
35
Ketone bodies are formed from ___-___ from FA oxidation
acetyl-CoA
36
Name the 3 ketone bodies
acetoacetate, beta-hydroxybutyrate; acetone
37
The ketone bodies are synthesized in ____ ____
liver mitochondria
38
___-___ is an intermediate in the ketone body pathway
HMG-CoA
39
The liver mitochondrial HMG-CoA synthase is an isozyme restricted to the mitochondria and functions only in what?
synthesis of ketone bodies
40
The cytosolic HMG-CoA synthase of many cells is the isozyme of ____ synthesis
cholesterol
41
Ketone bodies are utilized by peripheral tissues for energy - primarily the ___ and ____
muscle and brain note: the enzymes are mitochondrial
42
The ___ only produces ketone bodies, and the ___ ___ only utilizes ketone bodies
liver; peripheral tissue
43
Only liver mitochondria contain the enzymes specific for the synthesis of ketone bodies. What are they?
1. mitochondrial HMG-CoA synthase | 2. HMG-CoA lyase
44
Peripheral tissues (muscle and brain) express the enzyme specific for utilization of ketone bodies. What is it?
acetoacetate: succinyl-CoA transferase
45
True or false? ketone bodies are formed in the liver only when the liver is supplied with high concentrations of FAs
true
46
Where do the FAs used to synthesize ketone bodies come from?
lipolysis of adipose tissue
47
In what individuals is ketone body production usually seen?
starving or uncontrolled type 1 diabetes
48
After an over night fast, the concentration of ketone bodies in the blood is on the order of ____ mM. After a 2 day fast? After 40 days of starvation?
overnight: 0.05 2 days: 2mM 40 days: 7mM
49
____ is derived from the spontaneous, non-enzymatic decarboxylation of acetoacetate
acetone
50
The amount of FAs provided to the liver is under the control of ____ and ____
insulin and glucagon
51
This is the most common genetic disease of lipid metabolism (1/15000). It is associated with non-ketotic hypoglycemia upon fasting, fatty infiltration of liver, and short chain dicarboxylic acids in urine
MCAD (medium-chain acyl-CoA dehydrogenase) deficiency
52
In regards to MACD, non-ketotic hypoglycemia upon fasting may be deadly in an overnight fast of which individuals?
children
53
In regards to MACD, Fatty acids which cannot be oxidized are assembled into ____ which exceed the ability of the liver to secrete as ___
TAG; VLDL
54
In regards to MACD, the short chain dicarboxylic acids in the urine arise from where?
w-ocidation of medium and short chain fAs which can't be oxidized by beta-oxidation
55
What is the treatment of MACD?
avoid fasting
56
In this disorder of lipid oxidation, insufficient FAs are delivered into the mitochondria. Symptoms include non-ketotic hypoglycemia due to decreased energy for gluconeogenesis
carnitine deficiency
57
In this disorder of lipid oxidation, symptoms include non-ketotic hypoglycemia due to decreased beta-oxidation, hepatomegaly with fatty infiltration, increased plasma carnitine. It can be overcome by medium-chain FAs
CPT I deficiency
58
This disorder of lipid oxidation can be described by a rare genetic deficiency of a component required for peroxisomal oxidation of branched-chain FAs. Its associated with serious neurological issues.
Refsum disease
59
How is Refsum disease treated?
by reducing phytanic acid from diet (restrict dairy and meat)
60
This disorder of lipid oxidation is due to eating the unripe fruit of the akee tree, which contains hypoglycin - It is a potent inhibitor of acyl-CoA dehydrogenase. Symptoms are non-ketotic hypoglycemia
Jamaican vomitting sickness note: one case reported a blood glucose concentration of 3 mg/dl