Biology (Mader), 10th Edition

Chapter 3: The Chemistry of Organic Molecules

Energy Sources for Prolonged Exercise

What are the sources of energy in the body for physical activity? Biochemical pathways break down biomolecules to release energy. This energy is transferred to Adenosine Triphosphate (ATP) and is then used to power a wide variety of biological processes. Physical activity, such as exercise, requires a lot of ATP. The ATP comes from several different sources. Short term sources contain molecules that are readily broken down such as carbohydrates. Muscle glycogen is a form of carbohydrate that is easily accessible by muscles. Long term sources are molecules that are stored in the body such as lipids. Molecules used to store energy long term are often transported to the muscles through the circulatory system.

View the animation below, then complete the quiz to test your knowledge of the concept.



1.

A person who sprints for 45 seconds obtains most of their energy from
A)muscle triglycerides.
B)plasma free fatty acids.
C)blood glucose.
D)muscle glycogen.
2.

What happens to the amount of muscle glycogen used for energy as exercise continues?
A)it increases
B)it decreases
C)it continues unchanged
D)it is never used
3.

After 3 hours of exercise what are the main sources of energy?
A)blood glucose and plasma free fatty acids
B)blood glucose and muscle glycogen
C)blood glucose and muscle triglycerides
D)muscle glycogen and muscle triglycerides
4.

What happens to the amount of plasma free fatty acids used for energy as exercise continues?
A)they increase
B)they decrease
C)they continue unchanged
D)they are never used
5.

Where are most plasma free fatty acids obtained from?
A)hydrolysis of blood glucose
B)hydrolysis of muscle triglycerides
C)hydrolysis of stored fat
D)sports beverages
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