G. Related pathways pg 117

1] CARBOHYDRATES - Cells first choice for ‘food’ or energy broken down by simple aerobic cellular respiration

2. PROTEINS H H2N—C—COOH R Proteins breakdown into amino acids deaminase removes the amino [NH2] group The remainder enters the energy cycle at various points, eg: alanine  pyruvate leucine  acetyl-CoA proline  into Kreb’s

3. LIPIDS triglycerides  glycerol + 3 fatty acids

beta oxidation [into glycolysis] glycerol   3-phosphoglycerate 3 fatty acids  beta-oxidation beta oxidation most fatty acids are 18 carbons long

What does and 18-carbon fatty acid look like? H H H H H H H H H H H H H H H H H H-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C=O H H H H H H H H H H H H H H H H H OH How many carbons in acetyl-CoA? 2 carbons How many times do we have to cut the 18 carbon fatty acid? C-C C-C C-C C-C C-C C-C C-C C-C C-C 8 cuts

To calculate the energy released by lipid breakdown, there To calculate the energy released by lipid breakdown, there are two steps. Step One: beta-oxidation step that converts a long chain of carbons into a series of acetyl-CoA The oxidation of fatty acids into acetyl-CoA molecules requires the breaking of bonds, always one less bond that the number of acetyl-CoA. To break bonds, we must add water and ATP. When these fatty acid bonds are broken, 1 FADH2 and 1 [NADH + H+] are produced.

Given these steps, the beta-oxidation of an 18 carbon fatty Given these steps, the beta-oxidation of an 18 carbon fatty acid is shown below. 18 carbon fatty acid + 9 CoASH + 8 ATP + 8 FAD + 8 NAD+ + 8 H2O 9 acetyl-CoA + 8 ( ADP + Pi ) + 8 FADH2 + 8 ( NADH + H+ )

One turn through Kreb’s cycle produces Step two: the breakdown of the acetyl-CoA through the normal Kreb’s cycle. One turn through Kreb’s cycle produces 1 ATP: 1 FADH2: 3 [NADH + H+]. To determine the total number of high energy compounds produced this way, we must multiply these base numbers by the number of acetyl-CoA’s.

1 acetyl-CoA ATP FADH2 9 acetyl-CoA ATP FADH2 # # 1 9 3 27 1 9 NADH+H+

9 acetyl-CoA ATP FADH2 # 9 27 OXIDATION NET # # -8 ATP 1 ATP 8 35 8 NADH+H+ FADH2 # 9 27 OXIDATION NET # # -8 ATP 1 ATP 8 NADH+H+ 35 NADH+H+ 8 FADH2 17 FADH2

NET ATP FADH2 # 1 35 17 NET # 3 x GLUCOSE 1 ATP 105 3 x 36 ATP 34 ATP NADH+H+ FADH2 # 1 35 17 NET # 3 x GLUCOSE 1 ATP 105 3 x 36 ATP ATP 34 ATP 140 ATP total 108 ATP

Comparing 18 carbons of fatty acid with 18 carbons of glucose 18 carbons fatty acid  140 ATP 18 carbons of glucose  108 ATP Therefore we get 140 ATP / 108 ATP or 130 % energy from the lipid compared to glucose This is why we store energy on our bodies as fat!

Now try the two examples based on 12 carbons and 20 carbons