Fatty Acid Metabolism

Front 1

What is a triacylglycerol?

Back 1

TAG
fatty acids stored as TAG's

Front 2

What are 4 functions of fatty acids?

Back 2

1. energy stores

2. building blocks for phospholipids and glycolipids
sphingolipids

3. modifying proteins

4. hormones and secondary messengers

Front 3

What are the 4 steps of FA degradation?

Back 3

oxidation

hydration

oxydation

cleavage

Front 4

What are the 4 steps of FA synthesis?

Back 4

condensation

reduction

dehydration

reduction

Front 5

What does the degradation of a FA produce?

Back 5

an activated acetyl unit

acetyl CoA

Front 6

What two pieces come together in FA synthesis?

Back 6

Malonyl group and activated acyl group

Front 7

What is an activated acyl group?

Back 7

for our purposes it is the oxo-thioester part

O
ll
--C--S--R

Front 8

Describe what happens in degradation of FA.

Back 8

activated acyl group gets oxidized (makes a double bond) between the B and gamma carbon

the double bond is hydrated to make OH and CH2

the OH gets oxidized to a ketone (C=O)

coenzyme A cleaves the FA leaving it 2 carbons shorter

Front 9

What makes TAG's highly concentrated stores of metabolic energy?

Back 9

they are REDUCED and ANHYDROUS.

Front 10

What does oxidation of a FA give off in terms of energy?

Back 10

9 kcal/g (vs. 4 kcal/g for carbs)

Front 11

Where are TAG's stored?

Back 11

cytoplasm of adipocyte

Front 12

How are TAG's absorbed across the intestinal epithelium.

Back 12

They are not. They have to be degraded to FA's to go across.

Front 13

What degrades TAG's to free FA's and monoacylglycerols?

Back 13

lipases

Front 14

How do lipases, which in aq solution get to TAG's to degrade them?

Back 14

bile salts --glycocholate
wrap the TAG's in a water soluable cloak and incorporate them into micelles in the lumen of the intestine.

Front 15

Why would liver disease lead to steatorrhea?

Back 15

bile salts glycocholate are produced in the liver.

If bile acid production is decreased in liver from liver disease TAG's are not getting degraded as much and go out in the feces

Front 16

How do lipases work on the TAG's attached to micelles?

Back 16

They hydrolyze the TAG ester bond on surface of micelle creating free FA and monoacylglycerol (MAG)

Front 17

where are bile salts stored?

Back 17

gall bladder

Front 18

What happens after a TAG gets broken down into FA's and monoacylglycerol and transported over the intestinal epithelium?

Back 18

TAG's are resynthesized and packaged into chylomicrons.

Then the chylomicron "package" is dumped into the lymph and the blood where they lazy river it around to bind to membrane lipases (usually on fat cells and muscles) that break em down again for transport into the tissue

Front 19

What are chylomicrons?

Back 19

Big guys (200 nm) diameter

They contain TAG's, apolipoprotein B-48

they also transport fat soluable vitamins (VIT E) and cholesterol

Front 20

How do peripheral tissues gain access to adipose tissues energy stores?

Back 20

3 stages

1). lipids mobilized (turn TAG's back into FA's and MAG's and send em out)

2). at the target tissue, FA's have to be activated and transported into mitochondria

3. In mitochondria, the FA's are broken down into acetyl CoA and then GO CITRIC ACID CYCLE!!

Front 21

what catalyzes the hydrolysis of FA's in lipids?

Back 21

hormonall controlled lipases in adipose cells

Front 22

what hormones control the lipases in adipose tissues?

Back 22

epi, norepi, glucagon and ACTH

Front 23

how would epi release lipid energy stores?

Back 23

exercise induces epi which binds to the 7TM receptor on adipose cells. This binding activates adenylate cyclase to make cAMP

cAMP activates PKA which phosphorylates 2 key proteins

perilipin A and
hormone sensitive lipase

Front 24

What are the 2 key proteins in the hormone regulated lipase cascade?

Back 24

perilipin A

hormone sensitive lipase

When perilipin A gets phosphorylated it moves the TAG's into a position where hormone sensitive lipase can get to it better.

And then the phosphorylated hormone sensitive lipase hydrolyzes the TAG in free FA's.

Front 25

how does the insoluable FA's freed by lipolysis in the adipose cell get around the body?

Back 25

binds to serum albumin in the blood.

Front 26

What are the pieces released by hormone induced lipolysis in the adipose cells?

Back 26

glycerol and free FA's.

Front 27

Describe this picture.
What are the hormones?
Where is this taking place?

Back 27

epi, norepi, glucagon and ACTH bind to 7TM receptor and activate adenylate cyclase which makes cAMP which activates PKA which phosphorylates perilipin A and hormone sensitive lipase and degrades TAG's.

This is in the adipose cell

Front 28

What's the fate of the glycerol produced when lipolysis occurs?

Back 28

glycerol gets absorbed in the liver and gets phosphorylated by glycerol kinase.

Then, it gets oxidized by glycerol phosphate dehydrogenase to DHAP (then goes into glycolytic / gluconeogenic pathway)

Front 29

What are the 2 enzymes in the liver that get glycerol to the glycolytic pathway?

Back 29

glycerol kinase (just remember glycerol is what you are dealing with)

glycerol phosphate dehydrogenase (just remember you are oxidizing the phosphorylated glycerol phosphate)

If you wanna get really fancy pants remember that triose phosphate isomerase changes DHAP to GAP

Front 30

name these structures, enzymes and cofactors

Back 30

Front 31

What's the reaction that takes place on the outer mitochondrial membrane and what is the driving enzyme?

Back 31

activation of a FA

formation of a thioester linkage to coenzyme A before they go inside the mito matrix

enzyme = acyl CoA synthetase

Front 32

What are the 2 steps for activating FA

Back 32

FA + ATP form mixed anhydride acyl adenylate

PPi is released and hydrolyzed by pyrophosphatase

CoA-SH attacks acyl adenylate to form Acyl CoA + AMP

Equivalent of 2 ATP drives overall reaction

Front 33

What does FA react with ATP to form?

Back 33

acyl adenylate

Front 34

because the activation reaction of FA's is highly reversible what drives the rxn forward?

Back 34

pyrophosphatase readily hydrolyzes the pyrophosphate (2 PPi) given off after ATP makes the acyl adenylate with a FA

Front 35

So how does an activated FA get into the mitochondrial matrix?

Back 35

conjugates with carnitine

Front 36

What is carnitine?

Back 36

a zwitterionic alcohol

the acyl group transfers from Sulfur of CoA to the OH of carnitine

Front 37

Which enzyme piggy backs the acyl group of CoA onto carnitines OH?

Where does this take place?

Back 37

carnitine acyltransferase I

outer mitochondrial membrane

Front 38

what enzyme shuttles acyl carnitine from the outer mitochondrial membrane into the matrix?

Back 38

acyl carnitine translocase

Front 39

What enzyme catalyzes the transfer of the acyl group back to CoA in the inner mitochondrial matrix?

Back 39

carnitine acyltransferase II

Front 40

Name the structures and the enzyme that catalyzes this reaction

Back 40

Acyl CoA

Carnitine (note the structure and where the acyl group attaches)

acyl carnitine

Enzyme is carnitine acyltransferase I

Front 41

What are some symptoms associated with carnitine deficiency?

Back 41

muscle cramping and weakness

muscle , kidney and heart tissues usually most effected.

Front 42

Why is the degradation of acyl CoA called B-oxidation?

Back 42

Because as the 4 steps occur the fatty acid is shortened by 2 carbons and the oxidation takes place at the B carbon.

Front 43

What are the 2 oxidizing agents in B-oxidation of FA?

Back 43

FAD

NAD+

Front 44

What agent is responsible for the thiolysis step in B-oxidation of FA?

Back 44

CoA

Front 45

What enzyme catalyzes the oxidation of the B-carbon in B oxidation of FA?

Back 45

acyl CoA dehydrogenase

Front 46

what is the enzyme that catalyzes this reaction?

Back 46

acyl CoA dehydrogenase

Acyl CoA + E-FAD ---> trans^2enoly CoA + E-FADH2

Front 47

What is ETF?

What does it do?

Back 47

Electron-transferring Protein

accepts electrons from FADH2

Then it gives the electrons to ETF ubiquinone reductase

Front 48

What happens when electrons are given to ETF ubiquinone reductase?

Back 48

ubiquinone is reduced to ubiquinol and then it can do what it does in Complex III of electron transport chain

Q--->QH2

yields 1.5 ATP / FADH2

Front 49

Please explain the flow of electrons from the first step of B-oxidation pathway

Back 49

2 electrons go to

E-FADH2 to

ETF-FADH2 to

ETF: ubiquinone reductase where

ubiquinone goes to ubiquinol

Complex III in respiration!!

Front 50

Name all this stuff!

Back 50

Front 51

Name all the enzymes involved.

Back 51

Front 52

Name the enzymes

Back 52

Front 53

how many ATP are released from the oxidation of NADH in the respiratory chain?

Back 53

2.5 ATP

Front 54

How many ATP are produced from FADH2 making ubiquinol?

Back 54

1.5 ATP

Front 55

How many ATP are generated from acetyl CoA in citric acid cycle?

Back 55

10 ATP

Front 56

How many ATP are used up in the activation of FA?

Back 56

2 ATP

This is the cost of ATP to get all the ATP out of FA degradation.

Front 57

What's the stoichiometry of the complete oxidation of palmitoyl CoA?

Back 57

7 reaction cycles

palmitoyl CoA + 7 FAD + 7 NAD+ + 7 CoA + 7 H2O  8 acetyl CoA + 7 FADH2 + 7 NADH + 7 H+

Front 58

How many ATP does the complete oxidation of palmitoyl CoA yield?

Back 58

palmitoyl CoA + 7 FAD + 7 NAD+ + 7 CoA + 7 H2O  8 acetyl CoA + 7 FADH2 + 7 NADH + 7 H+

8 acetyl CoA (80 ATP), 7 FADH2 (10.5 ATP), 7 NADH (17.5 ATP)
total of 108 ATP
2 ATP equivalents used to activate palmitate
complete oxidation of palmitate gives 106 ATP

Front 59

What are the 2 additional enzymes needed in order to break down odd numbered or unsaturated FA's?

Back 59

isomerase and reductase

Front 60

What does cis-^3-enoyl CoA isomerase do?

Back 60

This is the enzyme that palmitoleate uses when it gets degraded to a cis double bond that is not a substrate for acyl CoA dehydrogenase.

It makes the cis^3 bond a trans^2 bond and the degradation continues from there normally.

Front 61

What is a peroxisome?

Back 61

small, membrane bound organelle which can oxidize FA's down to octanoyl CoA.

contain catalase

Front 62

How is peroxisomal oxidation different from mitochondrial B-oxidation in the 1st step?

Back 62

No FADH2 production

flavoprotein acyl CoA dehydrogenase transfers electrons to O2 to yield H2O2 instead of transfering electrons to FADH2 as in B-oxidation

Yikes, but catalase converts H2O2 to O2 and H2O.

Front 63

What must acetyl CoA combine with in order to enter into the citric acid cycle?

Where does this molecule come from?

Back 63

Oxaloacetate (OAA)

OAA comes from pyruvate, a product of glycolysis. Therefore in fasting or diabetes (when pyruvate is being used to run the gluconeogenesis pathway) there is none left over to make OAA and thus acetyl CoA has no buddy.

Front 64

What happens if there is no OAA to condense with acetyl CoA?

Back 64

acetyl CoA is diverted to make acetoacetate and D-3-hydroxybutyrate

(ketone bodies)

Front 65

What are acetoacetate (acetone) and D-3 hydroxybutyrate?

Back 65

ketone bodies.

produced when there is no OAA to condense with acetyl CoA in diabetes and fasting

Front 66

Where does the formation of acetone and D-3-hydroxybutyrate take place?

Back 66

liver

Front 67

what is the enzyme that reduces acetoacetate to D-3-hydroxybutyrate?

Back 67

D-3-hydroxybutyrate dehydrogenase

Front 68

What is the significance of acetone breath in an uncontrolled diabetes patient?

Back 68

it means there are a lot of ketone bodies.

ketone bodies are produce when there is no OAA to condense with acetyl CoA so it can go into citric acid cycle.
Therefore, acetoacetate and D-3-hydroxybutyrate are made and acetoacetate spontaneously decarboxylates to acetone in the blood.

Front 69

name the enzymes involved

Back 69

Front 70

Draw acetoacetate, D-3-hydroxybutyrate and acetone

Back 70

Front 71

What tissues use acetoacetate and 3-hydroxybutyrate instead of glucose?

Back 71

heart

renal cortex

Front 72

What tissues normally use glucose but can be trained to use ketone bodies for fuel?

Back 72

brain

Front 73

Since ketone bodies are a significant source of fuel how does the body get to the goodies of acetoacetone and D-3-Hydroxybutyrate?

Back 73

acetoacetate -->CoA transferase --> acetoacetyl CoA -->thiolase--> 2 acetyl CoA

Front 74

how do you get acetyl CoA from acetoacetate?

Back 74

Front 75

How do you get acetyl CoA out of 3-D-hydroxybutyrate?

Back 75

Have to do this step to get to acetoacetate and then do the break down from acetoacetate (CoA transferase) to Acetoacetyl CoA (thiolase) to 2 acetyl CoA

Front 76

Where does FA synthesis take place?

Where does FA degradation take place?

Back 76

synthesis--in cytosol

degradation--matrix of mitochondria

Front 77

What are intermediates attached to in FA synthesis?

In FA degradation?

Back 77

synthesis--acyl carrier proteins (ACP)

degradation--acetyl CoA

Front 78

What's the difference between the enzymes in FA synthesis vs. FA oxidation?

Back 78

In FA synthesis the enzyme is all on one Fatty acid synthase.

In FA oxidation all the enzymes are autonomous

Front 79

What's the starting block for FA synthesis?

Back 79

malonyl CoA

Front 80

In FA synthesis, what is the reductant used?

Back 80

NADPH

Front 81

Where does the elongation of FA synthesis halt?

Back 81

C 16
palmitate

Front 82

What's the first step in FA synthesis

Back 82

carboxylation of acetyl CoA via acetyl CoA carboxylase (isn't that name handy) to make malonyl CoA

Front 83

What's the first step in the synthesis of a FA?

What's the enzyme responsible

Draw the structures

Back 83

acetyl CoA carboxylase (ACC)

Front 84

What is the activated CO2 in the committed step of FA synthesis?

Back 84

Carboxyl group of biotin is attached to a E-lysine amino group.

1 ATP is used to get this CO2 on the biotin

This is the activated CO2 that then gets transferred onto acetyl CoA to make malonyl CoA

Front 85

What is an ACP?

Back 85

It's like a monster truck version of CoA.

Has SER-- phosphopantetheine group--SH

Front 86

What is FAS?

Back 86

a complex of distinct enzymes that catalyze FA synthesis
Has:
acetyl transacylase (AT)
malonyl transacylase (MT)
Acyl-malonyl ACP condensing enzyme
B-ketoacyl ACP reductase
2-Hydroxyacyl ACP dehydratase
enoyl ACP reductase

Front 87

What does acetyl transacylase do?

Back 87

transfers the acetyl group from acetyl CoA to the ACP

Front 88

What does malonyl transacylase do?

Back 88

transfers the malonyl group from malonyl CoA to ACP forming malonyl ACP + CoA

Front 89

Name the enzymes of FAS involved in FA synthesis

Back 89

Front 90

What enzyme starts FA synthesis of odd numberd FA's?

Back 90

propionyl ACP is formed when acetyl transacylase transfers propionyl group from propionyl CoA to propionyl ACP

Front 91

What are the 2 reactants in the condensation reaction in FA synthesis?

Back 91

acetyl ACP (made from Acetyl CoA and AT)

malonyl ACP (made from Malonyl CoA and MT)

Front 92

What is the enzyme that condenses Malonyl ACP with Acetyl ACP?
What is the resultant product?

Back 92

The acyl-malonyl ACP condensing enzyme (see how easy the naming is here--may be a mouthful but it makes sense!!!) portion of FAS

product is acetoacetyl ACP + ACP + CO2

Front 93

Why is the CO2 released from the condensation of malonyl ACP with Acetyl ACP significant?

Back 93

It drives the reaction because the release of the CO2 from Malonyl ACP decreases the free energy (favorable)

Front 94

Draw the condensation and subsequent reduction reactions in FA synthesis. Label enzymes and cofactors.

Back 94

Front 95

draw the dehydration and 2nd reduction reactions in FA synthesis. label cofactors, enzymes and structures

Back 95

Front 96

What's the general principle with regard to NAD+ and NADPH in biosynthetic reactions?

Back 96

NAD+ is the oxidizing agent

NADPH is the reducing agent

therefore NADPH is consumed in biosynthetic reaction and NADH is released.

Front 97

What are the starting blocks for the second round of fatty acid synthesis?

Back 97

malonyl ACP and butyryl ACP

Front 98

What's the overall stoichiometry of palmitate?

Back 98

8 acetyl CoA + 7 ATP + 14 NADPH + 6 H+ ---> palmitate + 14 NADP+ + 8 CoA + 6 H2O + 7 ADP+ + 7Pi

Front 99

Describe mammalian FAS?

Back 99

Huge homodimer 272 kDa subunits

3 domains connectd by flexible regions.

Front 100

What happens in domain 1 of FAS?

Back 100

substrate entrance and where the condensation action occurs (AT, MT, CE)

Front 101

How many acetyl CoA are needed for the synthesis of palmitate?

Back 101

Need 8 acetyl CoA

Front 102

Where is acetyl CoA formed?

Where does FA synthesis occur?

How do they get together?

Back 102

acetyl CoA is formed in mitochondrial matrix

FA synthesis takes place in cytosol

acetyl CoA piggy backs on OAA to make citrate which is transported to cytosol when there is a lot

Then ATP-citrate lyase in the cytosol breaks up citrate at the expense of ATP hydrolysis

Front 103

What is ATP-citrate lyase?

Back 103

The enzyme that breaks down citrate in the cytosol to yield acetyl CoA and OAA (ADP + Pi too of course)

Front 104

Why can't acetyl CoA cross the mitochondrial membrane?
How does it circumvent this obstacle?

Back 104

mitochondrial membrane is impermeable to acetyl CoA. Must couple with OAA to make citrate to get to the cytosol where it can make some FA's!

Front 105

Why are the bypass reactions which take place in order to get OAA into the mitochondria important?

Back 105

They generate much of the NADPH needed to make FA's.

Front 106

What are the bypass reactions needed to get OAA into the mitochondria

Back 106

OAA reduced to malate by malate dehydrogenase
OAA + NADH + H+--> malate + NAD+

decarboxylation by NADP+-linked malate enzyme
malate + NADP+ --> pyruvate + CO2 + NADPH

recarboxylation by pyruvate carboxylase
pyruvate + CO2 + ATP + H2O --> OAA + ADP + Pi + 2 H+

Front 107

How many NADPH are generated from each acetyl CoA that is transferred from matrix to cytosol?

Back 107

1 NADPH

Front 108

How many acetyl CoA do you need to make palmitate?

How many NADPH does this number generate?

Where do the remaining NADPH needed come from?

Back 108

8 acetyl CoA needed to make palmitate.

Therefore as the 8 acetyl CoA cross the mitochondrial membrane, 8 NADPH are generated.

Penthose Phosphate pathway

Front 109

Ugh. Describe this bad boy

Back 109

Front 110

when is FA synthesis maximal?

Back 110

when carbs and energy are plentiful and when fatty acids are scarce.

Front 111

What is essential in controlling and regulating FA synthesis?

Back 111

Acetyl CoA carboxylase catalyzes the production of malonyl CoA

Front 112

How is acetyl CoA carboxylase regulated?

Back 112

inhibited by AMP-dependent protein kinase (AMPK)

activated by Protein Phosphotase 2A (PP2A)

Front 113

How is AMPK like a fuel gauge?

Back 113

AMP present activates AMPK and thus phosphorylates the carboxylase and inactivates the creation of malonyl CoA

The presence of ATP, inactivates AMPK and tells PP2A to go which dephosphorylates the carboxylase and it converts acetyl CoA to malonyl CoA.

So when energy is abundant=go PP2A, go carboxylase

when energy is scarce=go AMPK, stop carboxylase

Front 114

What does AMPK do?

What effect does this have on FA synthesis?

Back 114

phosphorylates Acetyl CoA carboxylase

halts FA synthesis

Front 115

What does PP2A do?

What impact does this have on FA synthesis?

Back 115

dephosphorylates Acetyl CoA carboxylase

initiates the starting of FA synthesis by carboxylating Acetyl CoA to malonyl CoA

Front 116

How do epi and glucagon impact ACC?

Back 116

ACC stays phosphorylated

No FA synthesis

Front 117

How does insulin impact ACC?

Back 117

dephosphorylates ACC, go FA synthesis

Front 118

How does citrate impact ACC?

Back 118

follow me here:
when ATP and acetyl CoA are abundant citrate is too

means time is ripe for FA synthesis. converts the inactivated (phosphorylated) ACC into active filaments

Front 119

How does palmitoyl CoA and AMP impact ACC?

Back 119

antagonizes citrate

causes the active filaments that citrate turned ACC-Pi into, into inactive filaments.

Front 120

What is the difference in the enzymes that start oxidation between mitochondrial matrix oxidation versus peroxisomal oxidation?

Back 120

mito--acyl CoA dehydrogenase

periox--flavoprotein acyl CoA dehydrogenase

the flavoprotein guy is the electron transferrer from O2 to H2O2