Fatty Acid Oxidation Flashcards Preview

Digestive, Endocrine, and Metabolic Systems > Fatty Acid Oxidation > Flashcards

Flashcards in Fatty Acid Oxidation Deck (29):
1

What are the two most common disorders of fatty acid oxidation?

Carnitine deficiency and MCAD deficiency

2

True or false: all fatty acids need to be acylated (by fatty acyl co-a synthetase) to get into mitochondrial intermembrane space.

False. Only long-chain fatty acids do; short- and medium-chain fatty acids can diffuse across the mitochondrial membrane.

3

What inhibits carnitine acetyltransferase 1 and carnitine palmitoyltransferase 1?

Malonyl co-a. Think about it: malonyl co-a is a product in the synthesis of fatty acids, so it makes sense that something that signals fatty acid synthesis should inhibit the fatty acid breakdown pathway (otherwise it would be a futile cycle).

4

In the mitochondria, fatty acids can _____________.

be broken down via beta oxidation to produce acetyl co-a that generates NADH, FADH2, and GTP

5

Very long chain fatty acids must first be _________________ before going into the mitochondria.

degraded in peroxisomes

6

Hormone-sensitive lipase is active when ____________.

phosphorylated (because glucagon and epinephrine activate adenylyl cyclase and activate the protein kinase that phosphorylates hormone-sensitive lipase)

7

Acetyl co-a carboxylase is inhibited when ___________ (a covalent modification).

phosphorylated by the effects of epinephrine and glucagon binding; insulin activates a phosphatase that breaks the phosphate group off and activates this enzyme

8

Carnitine acetyltransferase binds acetyl groups to fatty acids, which can then ______________.

pass through the inner mitochondrial membrane (carnitine acetyltransferase is in the outer mitochondrial membrane)

9

Carnitine deficiency leads to massive accumulation of ________________.

fat within the cytosol of hepatocytes

10

Trace the beta oxidation pathway.

Cis acyl co-a (in mitochondria)
(Acyl co-a dehydrogenase) – generates a trans double bond
Trans acyl co-a
(Enoyl co-a hydratase) – adds H2O across the double bond
3-Hydroxyacyl co-a
(Beta-hydroxy-co-a-dehydrogenase) – oxidizes OH to O=
3-Ketoacyl-co-a
(Thiolase) – breaks off oxidized group
Acetyl co-a

11

One molecule of palmitoyl acid can produce _________.

131 molecules of ATP

12

Odd-numbered chains require ____________.

an extra step that adds a carboxyl group to the three-carbon remainder that ultimately gets put into the TCA cycle at succinyl co-a

13

Describe Zellweger syndrome.

deficiency in peroxisomal beta-oxidation enzymes, similar to X-linked adenoleukodystrophy

14

______________ is characterized by increased urinary excretion of carnitine esters, hypoglycemia, low levels of ketones during fasting state, and sleepiness.

Acyl co-a dehydrogenase deficiency (the most common disorder of beta-oxidation)

15

Beta-oxidation is regulated at the level of _______________.

carnitine acyltransferase

16

Ketone bodies are produced in the __________ in the presence of excess _____________.

liver; acetyl co-a

17

What happens to ketone bodies?

The liver does not have the enzyme to reconvert beta-hydroxybutyrate to acetyl-co-a, but the brain and muscles do. As such, ketones diffuse out to the peripheral tissues and are reconverted to acetyl co-a.

18

Why do those with T1DM produce ketones?

Lack of insulin leads to activation of hormone-sensitive lipase which creates more fatty acids. The excess fatty acids undergo beta-oxidation and produce excess acetyl co-a, which then leads to ketone conversion.

19

Qualitatively, what are the four steps of beta-oxidation?

Dehydrogenation
Hydration
Dehydrogenation
Cleavage

20

More than ________ percent of fatty acids in the body are stored as triglycerides.

90

21

Carnitine palmitoyl transferase is inhibited by ______________.

malonyl co-a (a signal of fatty acid synthesis)

22

What is produced by the four-step beta oxidation pathway?

1 FADH2
1 NADH
1 Acetyl co-a

23

Medium-chain fatty acyl dehydrogenase deficiency has been associated with ___________.

SIDS

24

Describe the process of ketogenesis.

During fatty acid oxidation, the elevated acetyl co-a and NADH lead to inhibition of pyruvate dehydrogenase and activate pyruvate carboxylase (producing oxaloacetate for gluconeogenesis). Additionally, the excess acetyl co-a favors ketone synthesis.

25

Trace the ketone synthesis pathway.

Acetyl co-a
(Thiolase)
Acetoacyl co-a
(HMG synthase)
HMG co-a
(HMG co-a lyase)
Acetoacetate
(3-hydroxybutyrate dehydrogenase) – produces NADH

26

Ketones are the primary fuel source in ____________.

the cardiac muscle and renal cortex

27

In order to use ketones, tissues must have ___________ to initiate conversion of 3-hydroxybutyrate to acteyl co-a.

thiophorase

28

The primary regulated step in fatty acid oxidation is ______________, while ___________ is the rate-limiting step.

hormone-sensitive lipase; CAT-1

29

Propionyl co-a will be found in ___________.

oxidation of odd-numbered fatty acids

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