Lipid Metabolism

Question 1

What are the 3 major steps of fatty acid catabolism?

Answer 1

1. Add CoA in cytosol
2. Transport into mito
3. Ovidize into acetyl-CoA by the B-oxidation pathway

Question 2

Can CoA cross the mito?

Answer 2

no. CoA is replaced with carnitine, aceyl-carnitine crosses mito, carnitine then replaced with CoA

Question 3

How many acetyl groups come from an 18-carbon fatty acid? 16?

Answer 3

18-C: cut 8 times to give 9 acetyl groups

16-C: cut 7 times to give 8 acetyl groups

Question 4

How many ATP’s per carbon are glucose and fatty acids worth?

Answer 4

glucose= 6.3 ATP’s per carbon

fatty acids= 8.1 ATP’s per carbon

Question 5

Why is it easier to break the bond during the formation of acetyl-CoA from a fatty acid between carbon 2 and 3?

Answer 5

The formation of a ketone on C3 allows for 2 electron withdrawing groups to exist on each side of C2 and draw the electrons away from the C-C bond, making it easier to break off

Question 6

carbon two on the fatty acid is ______ while carbon 3 is _______. Net redox?

Answer 6

carbon 2 is oxidized and carbon 3 is reduced. No net redox

Question 7

When there is one double bond in the fatty acid, a total of 144 ATP’s produced rather than 146. Why?

Answer 7

Because 1 FADH2 is failed to be produced during the oxidation of the unsaturated fatty acid

Question 8

What is the difference in production and consumption of reactants between a saturated fatty acid and an unsaturated fatty acid with TWO double bonds?

Answer 8

when 2 double bonds are present, we fail to produce one FADH2 and we consume 1 NADPH

Question 9

What happens when there is a low conc. of NADPH?

Answer 9

PPP speeds up and electrons from glucose are used to produce NADPH rather than NADH

Question 10

When the double bond is on an even or odd carbon, what happens?

Answer 10

even carbon = short an FADH2

odd carbon = consum an NADPH

Question 11

What happens to the glycerol of the fat?

Answer 11

the glycerol is metabolized by phosphorylation followed by oxidation into GAP
-can then be used in glycolysis or gluconeogenesis

Question 12

Where does the metabolism of glycerol occur?

Answer 12

in the cytosol

Question 13

Where does the addition of CoA to a fatty acid occur in the cell? What does this process consume?

Answer 13

in the cytosol

• occurs with the conversion of ATP into AMP and PPi
• equivalent to consuming 2 ATP

Question 14

Where does B-oxidation occur?

Answer 14

in the mitochondria

Question 15

How is it possible for plants to make sugar from fatty acids?

Answer 15

Using an odd chain fatty acid to generate succinyl-CoA, which can then generate more oxa, which can then go into gluconeogenesis