1. ATP and Energy Pathways
Module 3- Metabolism and Nutrition

2. ATP Work requires energy Energy is produced from ATP
Adenosine triphosphate has high energy bonds located between the phosphate groups
When this bond is broken energy is released (which can be used in the cell)

3. ATP ATP -> ADP + P + Energy
Hydrolyzation of ATP
This is an example of an exergonic reaction
This is also known as a chemical reaction
Chemical reactions are typically catalyzed by enzymes
ATPase
All enzymes end in “ase”

4. Figure 2.1 4

5. ATP The reverse reaction also occurs in the body
ADP + P + Energy -> ATP
Endergonic reaction
Where does this energy come from?
Food we eat
Carbohydrate, protein, fat
Metabolic pathways

6. Metabolic Pathways
Limited amount of ATP in the muscle cells

7. Metabolic Pathways 3 Main Metabolic Systems 4 Metabolic Pathways
Phosphagen System
Glycogen System
Oxidative System
4 Metabolic Pathways
Anaerobic
Phosphagen (ATP-PC, Creatine Phosphate)
Anaerobic Glycolysis
Aerobic
Aerobic Glycolysis
Oxidative

8. Metabolic Pathways PATHWAY TYPE LOCATION SUBSTRATE Rate Limiting Step
ATP-PC
Anaerobic
Cytoplasm
Creatine Phosphate
Creatine kinase
Glycolysis
Glucose
Phosphofructo- kinase
Krebs cycle
Aerobic
Mitochondria
Acetyl CoA
Isocitrate dehydrogenase
Electron transport system
Hydrogen delivered by NAD and FAD for oxidative phosphorylation
Cytochrome oxidase

9. Phosphagen System
Provides ATP primarily for short term, high intensity activities
Is active at the start of any activity, regardless of intensity
Uses the breakdown of another high energy phosphate molecule (creatine phosphate) to produce ATP
ADP + Creatine Phosphate ATP + Creatine
This creatine kinase reaction can produce ATP at a high rate, however, little creatine phosphate is stored
Creatine Kinase

10. Phosphagen System
At rest, the skeletal muscle concentration of creatine phosphate is 4-6x higher than ATP stores
Type II muscle fibers have a higher concentration of creatine phosphate than type I fibers
The phosphagen system is controlled throw the law of mass action
The concentrations of reactants or products (or both) in solution will drive the direction of the reactions

11. Glycolysis
The breakdown of carbohydrates—either glycogen stored in the muscle or glucose delivered in the blood—to resynthesize ATP
Involves multiple enzymatically catalyzed reactions, thus the rate of producing ATP is slower than the phosphagen system (however the capacity is higher due to larger stores of glucose)

13. Glycolysis End result is pyruvate, which has two possible paths:
Converted to lactate
Shuttled into the mitochondria
Anaerobic (fast) glycolysis
Pyruvate is converted to lactate
Produces ATP at a high rate but is limited in duration
The formation of lactate from pyruvate is catalyzed by the enzyme lactate dehydrogenase
The end result is not lactic acid
Lactate is not the cause of fatigue

14. Anaerobic Glycolysis
Glucose + 2 Pi + 2ADP Lactate + 2ATP + H2O
Lactate can be transported in the blood to the liver, where it is converted to glucose.
This process is referred to as the Cori cycle

15. Cori Cycle

16. Glycolysis Aerobic (slow) glycolysis
Occurs when pyruvate enters the mitochondria
Pyruvate that enters the mitochondria is converted to acetyl- CoA
Acetyl-CoA can then enter the Krebs cycle.
The NADH molecules enter the electron transport system, where they can also be used to resynthesize ATP
Glucose + 2Pi + 2ADP + 2NAD Pyruvate + 2ATP + 2NADH + 2H2O

18. Glycolysis Control of glycolysis Energy yield of glycolysis
Stimulated by high concentrations of ADP, Pi, and ammonia and by a slight decrease in pH and AMP
Inhibited by markedly lower pH, ATP, CP, citrate, and free fatty acids
Energy yield of glycolysis
Glycolysis from one molecule of blood glucose yields a net of two ATP molecules
Glycolysis from muscle glycogen yields a net of three ATP molecules

20. The Oxidative (Aerobic) System
Primary source of ATP at rest and low intensity exercise
Uses primarily carbohydrate and fat as substrates (protein can be used during starvation and very long bouts of exercise)

21. Carbohydrate Metabolism
Glucose and glycogen oxidation
Metabolism of blood glucose and muscle glycogen begins with glycolysis and leads to the Krebs cycle. (Recall: If oxygen is present in sufficient quantities, the end product of glycolysis, pyruvate, is not converted to lactate but is transported to the mitochondria, where it is taken up and enters the Krebs cycl.)
NADH and FADH2 molecules transport hydrogen atoms to the electron transport chain, where ATP is produced from ADP

23. Electron Transport Chain

25. Fat Oxidation
Triglycerides stored in fat cells can be broken down by hormone-sensitive lipase. This releases free fatty acids from the fat cells into the blood, where they can circulate and enter muscle fibers
Some free fatty acids come from intramuscular sources
Free fatty acids enter the mitochondria, are broken down, and form acetyl-CoA and hydrogen protons
The acetyl-CoA enters the Krebs cycle
The hydrogen atoms are carried by NADH and FADH2 to the electron transport chain

27. Protein Oxidation
Protein is not a significant source of energy for most activities
Protein is broken down into amino acids, and the amino acids are converted into glucose, pyruvate, or various Krebs cycle inter-mediates to produce ATP