We need energy to maintain the many chemical and physical activities of the body. As we have learned, all energy comes from the sun. Plants use this solar energy to perform chemical reactions to form carbohydrates, fats and protein. Humans, like animals, consume plants and other animals to obtain the energy required to maintain cellular activities. These cellular activities known as metabolism are maintained under homeostatic controls. These many chemical reactions occurring in our bodies must be regulated to maintain a balance between the trillions of cells in our body. These cells maintain balance through an intricate organization system. We will now discuss this intricate organized system known as the body.

Summary

We need energy to maintain the many chemical and physical activities of the body. All energy comes from the sun. Plants use solar energy to perform chemical reactions to form carbohydrates, fats and protein. Humans like animals consume plants and other animals to obtain the energy required to maintain cellular activities.

I. The body’s components work together in a highly organized manner to maintain a balance, this balance is known as homeostasis.

A. Metabolism can be defined as all of the chemical processes that occur in the body. Metabolism is categorized into two general phases; anabolism (building phase) and catabolism (breaking down phase).

B. The food you eat can either be burned to liberate energy, converted into bodyweight, or excreted.

The calories coming from protein are used for maintenance, repair, and growth of new tissues and organs. Calories from carbohydrates are used for energy. Calories from conventional sources of a fat are prone to be stored as fat since it already has the same molecular structure as body fat.

II. Energy metabolism is a series of chemical reactions that result in the breakdown of foodstuffs (carbohydrate, fat, protein) by which energy is produced, used, and given off as heat.

A. ATP, an acronym for adenosine triphosphate, is the molecule that stores energy in a form that can be used for muscle contractions.

1. Our muscle cells can produce ATP by any one or a combination of three metabolic pathways: the ATP/CP pathway, glycolytic pathway and/or oxidative pathway.




2. The formation of ATP without oxygen is known as anaerobic metabolism. This includes the ATP/CP and the anaerobic glycolytic pathway. Short-term activities at higher intensities utilize ATP production from anaerobic energy pathways.

   a. In the ATP/CP system, the P (phosphate) is separated from the C (creatine) and combines with ADP (adenosine di-, meaning two, phosphates) to reform ATP (adenosine tri-, meaning three, phosphates). One molecule of CP results in the reformation of 1 molecule of ATP. This system is sufficient for 3 to 15 seconds of ATP production.

   b. In non-oxidative glycolysis, glucose or glycogen is converted to lactic acid. One molecule of glucose results in 2 molecules of ATP and 1 molecule of glycogen results in 3 molecules of ATP. This system is reliable for 1 to 2 minutes of all out effort.

3. The formation of ATP with oxygen is known as aerobic metabolism. This includes the aerobic glycolytic pathway and the oxidative pathway. Long-term activities with a low to moderate intensity utilize ATP production from aerobic sources.

a. The aerobic metabolism of 1 molecule of glucose results in the production of 38 molecules of ATP and 1 molecule of glycogen results in the production of 39 ATP.

4. Glycogen is essential for both anaerobic and aerobic activities. Muscles being strenuously exercised will rely on glycogen to power strength generating muscle contractions. In endurance exercise, while the primary fuel is fatty acids, glycogen is also utilized.

5. Monitoring your metabolism is possible through Nitrostix or handheld, portable, indirect calorimeters.