Energy Sources for the Cell

Order of energy

1) ATP

2) Creatine phosphate

3) glucose

4) glycogen

5) lipids

6) proteins

What are the energy sources for the cell?

High energy carriers

• 1) ATP

• 2) Creatine phosphate

3) Anaerobic metabolism (with simple sugars)

4) Aerobic metabolism (with complex carbohydrates (glycogen) / lipids (triglycerides)

1) ATP

the cell uses the supply of ATP itself to meet its initial metabolic needs

• the body stores little ATP, and is cycled through ADP

• only store enough ATP for a few seconds of exercise

2) Creatine phosphate

once sparse ATP has been used, we can transfer phosphate molecules from creatine phosphate to ADP to reform ATP (through creatine phosphate shuttle)

• few more seconds of energy ~10 seconds

3) Anaerobic metabolism

• simple sugars

from simple sugars we get 4kcal/g, and have about 500g inside us for simple sugars

have the capacity to continue without oxygen for a limited amount of time, inefficient method as we only produce 2 ATP per glucose

can only use carbohydrate for energy anaerobically and lasts 30-60 seconds

4) Aerobic metabolism

nearly unlimited capacity to undergo; can use a variety of fuel sources to generate ATP (carbs, fats, proteins) in the presence of O2

Can provide energy for long period of time (hours)

4) Aerobic metabolism

• glycogen

4000kcal stored in glycogen

• 3000 kcal in liver

• 1000 kcal in muscle

3 hours of exercise

4) Aerobic metabolism

• lipids

9kcal/g

calorically dense because carbons are more reduced

10,000 kcal stored as fat

• enough to run 100 miles or sleep for months