Lecture 23: Metabolism of Fatty Acids

Question 1

Which of the following statements is INCORRECT about fatty acids?

-Saturated fatty acids have higher melting temperature than unsaturated fatty
acids.
-Naturally occurring unsaturated fatty acids mostly have double bonds in trans
configuration.
-ω-3 and ω-6 fatty acids are nutritionally essential fatty
-Polyunsaturated fatty acids such as arachidonic acid are used as precursors
to make eicosanoids

Question 2

Excess energy is stored as

Answer 2

fat

Question 3

Fatty acids are synthesized from

Answer 3

acetyl CoA

Question 4

Liver and adipose tissue convert

Answer 4

glucose to fatty acids to triacylglycerol

Question 5

Triacylglycerol

Answer 5

-leaves liver in VLDL lipoprotein
-enters blood
-stored in adipocytes

Question 6

adipocytes

Answer 6

-store triacylglycerol

Question 7

Brown fat cell

Answer 7

-many mitochondria producing heat with little fat particles scattered

Question 8

Fatty acid synthesis

Answer 8

-cytosol
-acetyl CoA +2 Carbons at a time
-carried by ACP or FA synthase through THIOester bond
-2 NADPH used per cycle
-carboxyl group of malonyl CoA released as CO2
-final product released from ACP by hydrolysis

Question 9

Transfer of acetyl CoA

Answer 9

-acetyl CoA from mitochondria cant cross membrane
-transported to cytosol as citrate

Question 10

Malonyl CoA

Answer 10

-substrate for FA synthesis
-inhibits FA oxidation

Question 11

Commitment step of FA synthesis

Answer 11

-acetyl CoA to Malonyl CoA by acetyl-CoA carboxylase
-use ATP

Question 12

Acetyl CoA carboxylase regulation

Answer 12

-Activated by citrate and isocitrate
_INHIBTED by acyl CoAs

Question 13

Acyl carrier protien (ACP)

Answer 13

-carries growing fatty acid chain thru thioester bond (covalent)
-releases final product by hydrolysis

Question 14

Modification of Fatty Acids

Answer 14

-palmitate can be elongated
-adding double bonds with desaturases

Question 15

palmitate

Answer 15

-humans synthesize as saturate C16 acid
-elongated by enzymes other than FA synthase (stearate = C18)

Question 16

Desaturases

Answer 16

-add double bonds to FA
-only up to the 9th carbon
-3,4,5 positions only act on FAs with doublle bond at 9th carbon
-omega 3 and omega 6

Question 17

essential fatty acids

Answer 17

-omega3
-omega6

Question 18

Hydrolysis of Triacylglycerol

Answer 18

-lipases
-triacylglycerol to glycerol and 3 FAs
-glycerol converted for either glyolysis or gluconeogenesis
-FAs used for energy production through OXIDATION

Question 19

Acyl CoA

Answer 19

-activate fatty acids
-used for oxidation or synthesis
-needs to be converted to acylcarnitine to get into mitochondria for oxidation (rate-limiting step)

Question 20

Acylcarnitine

Answer 20

-converted form of acyl CoA that can be transported into mitochondria from cytosol for FA oxidation

-RATE-LIMITING step of FA oxidation!

Question 21

RATE-LIMITING step of FA oxidation

Answer 21

transportation of acyl CoA to mitochondria as acylcarnitine

Question 22

Carnitine palmitoyltransferase (CPT I)

Answer 22

-INHIBITED by malonyl CoA

Question 23

B-oxidation

Answer 23

-2 Cs removed from acyl CoA as acetyl CoA at a time
-Produces NADH, FADH2, and Acetyl CoA
-go on to fuel TCA, substrate for ketone bodies and cholesterol

Question 24

Propionyl CoA (C3)

Answer 24

-FAs with odd number of carbons after B-oxidation
-can be converted to Succinyl CoA (ANAPLEROTIC)

Question 25

Oxidation of palmitate to acetyl CoA produces (in ATP)

Answer 25

26 ATP

Question 26

Synthesis of palmitate from acetyl CoA REQUIRES (in ATP)

Answer 26

49 ATP

Question 27

Compartmentation (Fatty acids)

Answer 27

-oxidation in mitochondria -synthesis in cytosol -prevents futile cycle