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Flashcards in FA Synthesis Deck (44):
1

In humans, the ___ is the main site for FA synthesis

liver

note: other sites include: kidney, brain, lung, mammary gland, and adipose

2

The process of FA synthesis occurs in what part of the cell?

cytoplasm

3

FAs are synthesized from 2 carbon units (acetyl-CoA). ___ is the main source of the acetyl-CoA, with some contribution from ___

glucose; AAs

note: other cofactors/substrates include: NADPH, ATP, biotin, and HCO3-

4

The process of using acetyl CoA to produce FA in the cytosol requires two important enzymes. What are they?

1. acetyl CoA carboxylase
2. FA synthase

5

When glucose is plentiful, glycolysis in the liver will produce "excess" ___ which enters mitochondria and produces ___-___ for the TCA cycle

pyruvate; acetyl-CoA

note: citrate, which is not further metabolized by the TCA can exit the mitochondria

6

In the cytosol, citrate is the substrate for ATP citrate lyase. What does this enzyme do? What does it require?

citrate is split back to oxaloacetate and acetyl-CoA

ATP is required

note: this enzyme is inducible

7

Cytosolic malate dehydrogenase reduces ___ to malate

OAA

8

What does the Malic enzyme do?

1. converts malate to pyruvate
2. produces NADPH which is necessary for FA synthesis

note: this enzyme is inducible

9

Acetyl-CoA carboxylase catalyzes the reaction producing ___-___ from acetyl-CoA

malonyl-CoA

10

Acetyl-CoA carboxylase requires ___ and is the rate-limiting enzyme of ___ ___

biotin; FA synthesis

11

Acetyl-CoA carboxylase is the regulated step of FA synthesis. It exists as either inactive ___ __ or as active ___.

proteomeric dimers; polymers

12

Acetyl-CoA carboxylase is stimulated by what? inhibited by what?

stimulated by citrate (feed forward)
inhibited by long-chain fatty acyl-CoA (feed back)

13

Acetyl-CoA carboxylase is also controlled by phosphorylation/dephosphorylation. True or false?

true

note: an AMP-dependent protein kinase phosphorylates the enzyme

14

Phosphorylation causes ___ of acetyl-CoA carboxylase?

inactivation

15

In regards to acetyl-CoA carboxylase, AMP would increase during times of ____

fasting

16

Glucagon stimulates the activity of the AMP-dependent kinase, which results in ___ of FA synthesis

inhibition

note: mechanism via cAMP-dependent protein kinase

17

A protein phosphatase dephosphorylates acetyl-CoA carboxylase. This causes ___ of the enzyme. This protein phosphatase is stimulated by ___

activation; insulin

18

Prolonged consumption of a diet containing excess calories results in increased synthesis of this enzyme

acetyl-CoA carboxylase

note: a low-calorie diet reduces synthesis of this diet

19

FA synthase is a multi-functional enzyme in eukaryotes. It is active as a ___. Each monomer contains ___ different enzymatic activities.

dimer; 7

20

FA synthase allows only one fatty acyl chain to be synthesized at a time. True or false?

false; two fatty acyl chains

21

FA synthase sequentially adds two-carbon units from ___-___ to a growing ___ ___ chain

malonyl-CoA; fatty acyl

22

The starting unit of FA synthase is ___-___ and the product is ____

acetyl-CoA; palmitate

23

1. In the first round of the synthesis cycle, acetyl transacylase adds an acetyl group to the ___ of a cysteine residue of ketoacyl synthase domain of one monomer

SH

24

2. Malonyl transacylase adds a malignly group to the SH of the ____-___ group of acyl carrier protein (ACP) domain of the other monomer

phospho-pantetheine

25

3. 3-ketoacyl synthase catalyzes the FA synthase reaction adding the acetyl group to the malignly group and decarboxylation, leaving the product (a 3-ketoacyl group) bout the the ___ domain

ACP

26

4. 3-ketoacyl reductase reduces the 3-keto group to an hydroxyl, using ___ as the reducing agent

NADPH

27

5. The hydrates catalyzes the removal of H2O resulting in a ___-___ group

2-enoyl

28

6. The enoyl reductase saturates the carbon-carbon double bond to produce a saturated acyl group (2 carbons longer) using ___ as the reducing agent

NADPH

29

7. The lengthened acyl group is transferred from the ACP domain to the opposite monomers ____ ____ cysteine residue for another round

ketoacyl synthase

note: for each round, 2 carbons are added from malonyl-CoA

30

8. A total of 7 rounds is completed to form a palmitoyl group. After the 7th round, the _____ hydrolyzes the palmitate from the ACP domain

thioesterase

31

In order to be further metabolized, the palmitate is converted to palmitoyl-CoA for what 4 things?

1. esterfircation to triacylglycerols
2. elongation
3. desaturation
4. esterfication to cholesteryl ester

32

Give the 2 steps of the overall equation for palmitate synthesis

1. from acetyl-CoA and malonyl-CoA
2. from acetyl-CoA to palmitate - must account for ATP used by acetyl-CoA carboxylase

33

The major source of NADPH is the ___ ___ pathway with some provided by magic enzyme

pentose phosphate

34

FA elongation occurs primarily in the ____ ___

endoplasmic reticulum

35

The preferred substance of FA elongation is ____-___. The preferred product is ____-___

palmitoyl-CoA; stearoyl-CoA (18:0)

36

The formation of mono-unsaturated FAs begins with stearoyl-CoA desaturase which is an enzyme of the ER that requires what?

NADH or NADPH, molecular O2, cytochrome b5

37

In regards to stearoyl-CoA desaturase, the desaturation always occurs at carbon ___

9

38

The product of stearoyl-CoA denatures is what?

oleoyl-CoA or palmitoleoyl-CoA

39

Poly-unsaturated FAs have 2 important functions. What are they?

1. increase membrane fluidity
2. source of important bio-active compounds (eicosanoids)

40

Formation of PUFAs depends on chain ____ and introduction of ___ bonds

elongation; double

41

Humans cannot introduce a double bond beyond carbon ___

9

42

FAs derived from oleic acid are referred to as w-9 or n-9. Why?

because the first double bond encountered rom the w or n carbon is 9 carbons toward the carboxyl carbon

43

Since humans cannot add double bonds beyond carbon 9, some FAs are required in the diet. Name 2 of these.

w-6 FA: linoleic acid is an essential FA

w-3 FA: alpha-linolenic acid is an essential FA

44

Synthesis of ____ acid is an example of synthesis of an important PUFA from an essential FA

arachidonic