Using Fats and Proteins as Energy Sources PSK 4U Day 4

Overview of the Three Energy Systems See chart in textbook

Fat and Protein as Energy Sources So far we have mainly discussed how ATP is produced from carbohydrate (glucose/glycogen) both anaerobically (glycolysis) and aerobically (cellular respiration). The body also uses fats and proteins as well. During physical activity, the primary sources are carbohydrates and fats. Protein is less accessible so contributes a relatively small percentage of total energy used.

FAT Fats are ideal fuel sources because they contain large quantities of stored energy. Dietary fat is broken down in liver during digestion into fatty acids and glycerol. Fatty acids are stored in our tissues (muscle and adipose tissue) as triglycerides (a chain of three fatty acids).

FAT Ultimately, fatty acids are converted in a process called beta oxidation to acetyl-CoA which feeds into the Kreb’s Cycle. The glycerol is converted into pyruvate which is also converted to acetyl-CoA and enters the Kreb’s Cycle under aerobic conditions.

FAT BURNING and DIET Low carbohydrate diets – Atkins, Paleo, primal, caveman...

FAT BURNING and EXERCISE

Sugars , carbohydrates Triglycerides glycerol glycolysis pyruvate Kreb’s Electron Transport Chain

PROTEIN Protein contains roughly the same amount of energy as carbohydrate, but unlike carbohydrates and fats, there are no stored protein reserves. All proteins are part of existing body tissue or are actively engaged as components of the metabolic system. Protein in the body is composed of twenty different amino acids, which are used by the body to form various body tissues. Nine of these (called essential amino acids) cannot be synthesized by the body and must be consumed as food. To be used as an energy source, protein must first be broken down into amino acids. Alanine, one of these amino acids, is the main contributor to our energy system since it is converted in the liver to glycogen which is transported as glucose to the working muscles.

PROTEIN Protein, as an energy source, plays an important role in endurance-type activities and more generally in chronically glycogen-depleted conditions. The body uses protein as a kind of energy backup in the absence of adequate levels of other energy sources. In this respect, use of protein in endurance events has been said to mimic conditions created during short-term starvation