W2-L2: Energy Systems Flashcards
What are the 3 Main Energy Systems used by the Body?
When are each of them used?
What is the Phosphagen Energy System?
Uses phosphocreatine exclusively to regenerate ATP in muscle tissue, simple chemical reaction
(not a metabolic pathway)
produced by liver and got from meat
How is Phosphocreatine used for energy?
- Split into creatine and a Pi by creatine kinase
- The additional Pi from the phosphocreatine compound used to resynthesize ADP into ATP
- This specific reaction occurs in the cytosol
What is Glycolosis?
When does it Take over?
Where does it take place?
Can yoy stimulate the Process?
- Glycolysis: one molecule of glucose is converted into two molecules of pyruvate, 2 H+ ions and 2 molecules of water
- Fuels all-out exercise efforts after phosphagen system has been exhausted (approx. 15 seconds)
- Features a 10-step process, occurs in cytosol
- Stimulated by epinephrine
happens in the abscene of O2
What are the overall products of Glycolosis?
2 ATP (net gain)
2 NADH
2 Pyruvate
2 H₂O
Converts 1 6-C glucose to 2 x 3-C Pyruvate molecules
What is happening during the Glycolosis Pathway?
How does Glucose get into the cell?
Glucose comes from either the food we eat or from the breakdown of glycogen in the liver
It is transported by GLUT 4 across the cell membrane
What is the purpose of Hexokinase?
- breakes down glucose into: Glucose 6-phosphate
- Uses an ATP (energy consuming rxn)
- The glucose can no longer leave the cell (non-reversible)
In the liver, a different enzyme is is used in which the process is reversible
How is Step 1 different if Glycogen is the starting substrate instead of Glucose?
When using glycogen, it is possible to form Glucose 6-phosphate without consuming an ATP
Therefore 1 more molecule of ATP would be produced overall
What is the rate-limiting enzyme in Glycolosis?
phosphofructokinase
- becomes inhibited once ATP lvls are too high
What are the Two pathways pyruvate can take after glycolosis?
What happens to pyruvate in abscene of O2?
- Pyruvate undergoes fermentation to regenerate NAD+, which is essential for glycolysis to continue.
- pyruvate is converted into lactate via lactate dehydrogenase.
- This pathway does not produce additional ATP beyond the 2 ATP molecules generated during glycolysis.
What happens to pyruvate in presence of O2?
PYRUVATE CONVERSION TO ACETYL COA:
- Catalyzed by Pyruvate Dehydrogenase Complex
- Regulated by energy status of the cell
- high ATP will slow down PDC activity
- high ADP levels will speed it up
Pyruvate Dehydrogenase Complex = Rate-Limiting Enzyme
