1. G. Related pathways
pg 117

2. 1] CARBOHYDRATES
- Cells first choice for ‘food’ or energy
broken down by simple aerobic cellular respiration

3. 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

4. 3. LIPIDS
triglycerides 
glycerol + 3 fatty acids

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

6. 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

7. 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, FADH2 and 1 [NADH + H+] are produced.

8. 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
CoASH
+ 8 ATP
+ 8 FAD
+ 8 NAD+
+ 8 H2O
9 acetyl-CoA
+ 8 ( ADP + Pi )
+ 8 FADH2
+ 8 ( NADH + H+ )

9. 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.

10. 1 acetyl-CoA ATP FADH2 9 acetyl-CoA ATP FADH2 # # 1 9 3 27 1 9 NADH+H+

11. 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

12. 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
ATP

13. Comparing 18 carbons of fatty acid with 18 carbons of glucose
18 carbons fatty acid  ATP
18 carbons of glucose  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!

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