Fatty Acids

Question 1

Give step three of glycerol metabolism

Answer 1

In step three, Dihydroxyacetone phosphate is converted to d-Glyceraldehyde 3-phosphate by triose phosphate Isomerase.

Question 2

Give step two of glycerol metabolism

Answer 2

In step two, L-Glycerol 3-phosphate is converted to Dihydroxyacetone phosphate by glycerol 3-phosphate dehydrogenase.

Question 3

Give step one of glycerol metabolism

Answer 3

Glycerol is converted to L-Glycerol 3-phosphate by glycerol kinase.

Question 4

Give the equation of the activation of FFA

Answer 4

fatty acid + CoA + ATP <——> fatty acyl-CoA + AMP + 2Pi

Thus, acyl–CoA synthetases catalyze the formation of a thioester linkage between the fatty acid carboxyl group and the thiol group of coenzyme A to yield a fatty acyl– CoA, coupled to the cleavage of ATP to AMP and PPi.

Question 5

Can the majority of the FFA obtained in the diet or released from adipose tissue pass directly through the mitochondrial membrane?

Answer 5

No, they must first undergo the three enzymatic reactions of the carnitine shuttle.

Question 6

Where are neutral lipids stored?

Answer 6

In adipocytes and in steroid-synthesizing cells of the adrenal cortex, ovary, and testis.

Question 7

Neutral lipids are stored in adipocytes (and in steroid- synthesizing cells of the adrenal cortex, ovary, and testis) in the form of lipid droplets. The surface of these droplets is coated with ______?

Answer 7

Perilipins, a family of proteins that restrict access to lipid droplets, preventing untimely lipid mobilization.

Question 8

When hormones signal the need for metabolic energy, triacylglycerols stored in adipose tissue are _______?

Answer 8

Mobilized (brought out of storage) and transported to tissues (skeletal muscle, heart, and renal cortex) in which fatty acids can be oxidized for energy production.

Question 9

What stimulates the enzyme adenylyl cyclase in the adipocyte plasma membrane?

Answer 9

The hormones epinephrine and glucagon

Question 10

The enzyme adenylyl cyclase triggers the intracellullar second messenger ________

Answer 10

Cyclic AMP

Question 11

What does Cyclic AMP dependent protein Kinase do?

Answer 11

Triggers changes that open the lipid droplet up to the action of three lipases, which act on tri-, di-, and monoacylglycerols, releasing fatty acids and glycerol. These then get released in the blood.

Question 12

Free fatty acids released into the blood binds to?

Answer 12

The blood protein serum albumin.

Question 13

Why are the free fatty acids bound to serum albumin?

Answer 13

To allow the otherwise insoluble fatty acids to be carried to tissues such as skeletal muscle, heart, and renal cortex.

Question 14

What happens after the fatty acids dissociate from albumin?

Answer 14

They are moved by plasma membrane transporters into cells to serve as fuel. The glycerol liberated by lipase action is phosphorylated and oxidized to dihydroxyacetone phosphate, which can enter the glycolytic or gluconeogenic pathways. Alternatively, glycerol phosphate can be used in triacylglycerol or phospholipid synthesis.

Question 15

About 95% of the biologically available energy of triacylglycerols resides in their?

Answer 15

In their three long-chain fatty acids; only 5% is contributed by the glycerol moiety.

Question 16

Where are the enzymes for fatty acid oxidation in animal cells located?

Answer 16

In the Mitochondrial matrix

Question 17

Fatty acids with 14 or more carbons cannot pass directly through the mitochondrial membrane, they must first _______?

Answer 17

They must first undergo the three enzymatic reactions of the carnitine shuttle.

Question 18

Give the general equation for the first reaction in the Carnitine shuttle.

Answer 18

Fatty acid + CoA + ATP <—> fatty acyl–CoA + AMP + 2 Pi

Question 19

Fatty acyl–CoA esters formed at the cytosolic side of the outer mitochondrial membrane can be transported into the mitochondrion and oxidized to produce ?

Answer 19

ATP, or they can be used in the cytosol to synthesize membrane lipids.

Question 20

Fatty acids destined for mitochondrial oxidation are transiently attached to?

Answer 20

The hydroxyl group of carnitine to form fatty acyl–carnitine—the second reaction of the shuttle.

Question 21

Fatty acids destined for mitochondrial oxidation are transiently attached to the hydroxyl group of carnitine to form fatty acyl–carnitine—the second reaction of the shuttle. This transesterification is catalyzed by?

Answer 21

Carnitine acyltransferase I in the outer membrane

Question 22

After passage into the intermembrane space through large pores (formed by the protein porin) in the outer membrane, the fatty acyl–carnitine ester then enters ______?

Answer 22

The Matrix by facilitated diffusion through the acyl-carnitine/carnitine transporter of the inner mitochondrial membrane.

Question 23

What is the third and final step of the carnitine shuttle?

Answer 23

In the third and final step of the carnitine shuttle, the fatty acyl group is enzymatically transferred from carnitine to intramitochondrial coenzyme A by carnitine acyl- transferase II.

Question 24

What does carnitine acyl-transferase II do?

Answer 24

regenerates fatty acyl–CoA and releases it, along with free carnitine, into the matrix.

Question 25

The three steps for transferring fatty acids into the mitochondrion (Carnitine shuttle) are?

Answer 25

Esterification to CoA, trans-esterification to carnitine followed by transport, and transesterification back to CoA.

Question 26

Describe the first stage of fatty acid oxidation

Answer 26

The fatty acids undergo oxidative removal of successive two-carbon units in the form of acetyl-CoA, starting from the carboxyl end of the fatty acyl chain.

Question 27

Describe the second stage (of three) of fatty acid oxidation

Answer 27

In the second stage of fatty acid oxidation, the acetyl groups of acetyl-CoA are oxidized to CO2 in the citric acid cycle, which also takes place in the mitochondrial matrix. Acetyl-CoA derived from fatty acids thus enters a final common pathway of oxidation with the acetyl-CoA derived from glucose via glycolysis and pyruvate oxidation.

Question 28

Describe the third stage (last stage) of fatty acid oxidation.

Answer 28

The first two stages of fatty acid oxidation produce the reduced electron carriers NADH and FADH2, which in the third stage donate electrons to the mitochondrial respiratory chain, through which the electrons pass to oxygen with the concomitant phosphorylation of ADP to ATP. The energy released by fatty acid oxidation is thus conserved as ATP.

Question 29

The beta oxidation of saturated fatty acids have how many steps?

Answer 29

Four (4)

Question 30

Describe the first (of four reactions) of the first stage of saturated fatty acid oxidation.

Answer 30

First, dehydrogenation of fatty acyl–CoA produces a double bond between the a and B carbon atoms (C-2 and C-3), yielding a trans-D2-enoyl-CoA (the symbol D2 designates the position of the double bond. This first step is catalyzed by three isozymes of acyl- CoA dehydrogenase, each specific for a range of fatty-acyl chain lengths. The electrons removed from the fatty acyl–CoA are transferred to FAD, and the reduced form of the dehydrogenase immediately donates its electrons to an electron carrier of the mitochondrial respiratory chain, the electron-transferring flavoprotein (ETF).

Question 31

Describe the second (of four reactions) of the first stage of saturated fatty acid oxidation.

Answer 31

In the second step of the B-oxidation cycle water is added to the double bond of the trans- D2-enoyl-CoA to form the L stereoisomer of B-hydroxy-acyl-CoA (3-hydroxyacyl-CoA). This reaction, cata- lyzed by enoyl-CoA hydratase, is formally analogous to the fumarase reaction in the citric acid cycle, in which H2O adds across an a-B double bond.

Question 32

What separates the three fatty acids from their glycerol backbone?

Answer 32

Lipolysis

Question 33

Which type of reaction does each of the four beta oxidation steps fall into?

Answer 33

1. oxidation (acyl-CoA dehydrogenases (AD): short chain, medium chain and very long chain) 2. hydration (enoyl-CoA hydratase) 3. oxidation (β hydroxyacyl-CoA dehydrogenase) 4. cleavage (acyl-CoA acetyltransferase)

Question 34

Outline the beta oxidation of unsaturated FFA

Answer 34

Oleoyl-CoA becomes cis-D3-Dodecenoyl-CoA by three cycles of beta oxidation. Cis-D3-Dodecenoyl-CoA in turn becomes trans-D2-Dodecenoyl-CoA by D3,D2-enoyl-CoA isomerase. Lastly trans-D2-Dodecenoyl-CoA becomes 6 Acetyl-CoA by 5 beta oxidation cycles

Question 35

VLCAD acts on fatty acids of what length?

Answer 35

12 to 18 carbons

Question 36

MCAD acts on fatty acids of what length?

Answer 36

4 to 14 carbons

Question 37

SCAD acts on fatty acids of what length?

Answer 37

4 to 8 carbons.

Question 38

True or false? The three isozomes VLCAD, MCAD, SCAD are flavoproteins with FAD.

Answer 38

True. The electrons removed from the fatty acyl–CoA are transferred to FAD, and the reduced form of the dehydrogenase immediately donates its electrons to an electron carrier of the mitochondrial respiratory chain, the electron-transferring flavoprotein (ETF)

Question 39

The oxidation catalyzed by an acyl-CoA dehydrogenase is analogous to _______ in the citric acid cycle.

Answer 39

Succinate dehydrogenation

Question 40

The second step of the B-oxidation cycle (water is added to the double bond of the trans- D2-enoyl-CoA to form the L stereoisomer of B-hydroxy- acyl-CoA) is analogous to the ________ reaction in the citric acid cycle.

Answer 40

fumarase

Question 41

The third step of beta oxidation (L-B-hydroxyacyl-CoA is dehydrogenated to form B-ketoacyl-CoA) is analogous to _______ reaction in the citric acid cycle.

Answer 41

Malate dehydrogenase

Question 42

The four B-oxidation steps yield?

Answer 42

Acetyl-CoA and ATP

Question 43

How much ATP is generated from the pair of electrons from FADH2 after fatty acid oxidation?

Answer 43

1.5 molecules of ATP

Question 44

Give the overall equation for the oxidation of palmitoyl-CoA.

Answer 44

Palmitoyl-CoA + 7CoA + 7O2 + 28Pi + 28ADP—> 8 acetyl-CoA + 28ATP + 7H2O

Question 45

How much ATP is formed from the oxidation of Palmitoyl-CoA?

Answer 45

108

Question 46

Outline the activation of FA

Answer 46

The carboxylate ion is adenylated by ATP by fatty acyl-CoA synthetase to form a fatty acyl-adenylate and PPi. The PPi is immediately hydrolyzed into two molecules of Pi. The thiol group of CoA then attacks acyl-adenylate (a mixed anhydride), displacing AMP and forming the thioester fatty Acyl-CoA

Question 47

On which group on Carnitine are fatty acids attached?

Answer 47

The hydroxyl group

Question 48

What is the mitochondrial CoA pool used for?

Answer 48

Oxidative degradation of pyruvate, fatty acids and some aa’s.

Question 49

Hat is the cytosolic CoA pool used for?

Answer 49

Biosynthesis of fatty acids

Question 50

What is the rate limiting step in FFA transport?

Answer 50

The movement of Fatty acyl CoA from the cytosol into the mitochondria via the Carnitine shuttle

Question 51

Give the first step of fatty acid synthesis

Answer 51

Condensation

Question 52

Give step two of fatty acid synthesis

Answer 52

Reduction

Question 53

Give step three of fatty acid synthesis

Answer 53

Dehydration

Question 54

Give step four (last step) of fatty acid synthesis.

Answer 54

Reduction