metabolism of fatty acids

Question 1

storing excess energy as fat

Answer 1

-excess energy is stored as the form of fat
-fatty acids are synthesized from acetyl CoA
-the liver and adipose tissue converts glucose to farry acids and then to triacylglycerol
-liver releases triacylglycerol to blood stream after packing it in lipoproteins
-adipocytes store triacylglycerol

Question 2

transfer of acetyl CoA

Answer 2

-fatty acid synthesis occurs in cytosol
-acetyl CoA is produced in the mitochondria
-instead of acetyl CoA, citrate is transported to the cytosol

Question 2

malonyl CoA

Answer 2

-conversion of acetyl CoA to malonyl CoA is the commitment step of fatty acid synthesis
-acivity of acetyl CoA carboxylase is highly regulated (activated by citrate and isocitrate, inhibited by acyl CoAs)
-malonyl CoA is used as a substrate for fatty acid synthsis
-malonyl CoA inhibits fatty acid oxidation

Question 2

fatty acid synthesis

Answer 2

-synthesis starts with acetyl CoA by adding 2 carbon untis
-during synthesis, growing fatty acids are carries by acyl carrier proteins or fatty acid synthase through covalent bonds
-fatty acid synthase is a multifunctional enzyme
-2 NADPH used per cycle
-carboxyl group of malonyl CoA is released as CO2 during synthesis
-final product is released by ACP by hydrolysis

Question 3

modification of fatty acids

Answer 3

-human synthesize the saturated C16 acid first
-palmiate can be elongated further by enzymes other than fatty acid synthase

Question 3

double bonds are added by desaturases

Answer 3

-human can add double bonds only up to the 9th carbon
-desaturatases for 4,5,6 positions act only on fatty acids with double bond at 9th carbon
-W3 and W6 fatty acids are essential fatty acids

Question 4

hydrolysis of triacylglycerol

Answer 4

-tricylglycerol is the major fat in our diet and in adipose tissue
-lipases hydrolyzes tricylclycerol to glycerol and three fatty acids
-glycerol is converted to an intermediate for glycolysis or gluconeogenesis
-fatty acids are used for energy production through fatty acid oxidation

Question 5

transport of fatty acids

Answer 5

-Fatty acids are activated by forming acyl CoA.
-Acyl CoA is used for fatty acid oxidation or
triacylglycerol synthesis.
- Acyl CoA in the cytosol need to be converted to
acylcarnitine for transport into mitochondria for fatty
acid oxidation, which is the rate-limiting step for
fatty acid oxidation.
-Carnitine palmitoyltransferase I (CPT I) is inhibited
by malonyl CoA.

Question 6

B-oxidation

Answer 6

-Two-carbon unit is removed from acyl CoA as acetyl
CoA (C 2) at a time
-NADH, FADH 2, and acetyl CoA are produced.

Question 7

Acetyl CoA is used as the fuel of ______ or as a substrate for ketone bodies and cholesterol

Answer 7

TCA cycle

Question 7

fatty acids with an odd number of carbons produce a propionyl CoA at the end of the cycle

Answer 7

-C16 fatty acid–> 8 acetyl CoA
-C17 fatty acid –> 7 acetyl CoA and 1 propionyl CoA

Question 7

propionyl CoA can be converted to _____ which is an anaplerotic reaction

Answer 7

succinyl CoA

Question 8

Fatty acid oxidation vs fatty acid synthesis

Answer 8

-The oxidation of palmitate to acetyl CoA produces
26 ATP equivalent.
-The synthesis of palmitate from acetyl CoA requires
49 ATP equivalent.
-The simultaneous activation of the both pathways will
form a futile cycle.
-Fatty acid oxidation occurs in the mitochondria, and
fatty acid synthesis occurs in the cytosol
(compartmentation)