The Krebs cycle, also known as the citric acid cycle or tricarboxylic acid cycle, is a vital part of the process that allows you to use the energy contained in food. Your body can't begin the Krebs cycle unless it has sufficient sources of a substance called glucose. Foods in your diet that contain carbohydrates are a major glucose source.
Carbohydrates and Glucose
Carbohydrates are groupings of different types of sugar, which plants create during photosynthesis. One form of these sugars, called a simple carbohydrate, contains either single sugar molecules or molecules joined in pairs. Another form, called a complex carbohydrate, contains longer chains of sugar. When you eat carbohydrate-containing plants, or foods obtained from plant sources, your body breaks them down in your stomach and small intestine and passes the simple sugar glucose to your bloodstream. In turn, glucose passes to cells in various parts of your body, where it enters energy-generating structures called mitochondria.
Understanding the Krebs Cycle
The Krebs cycle gets its name from a biochemist named Hans Krebs, who first identified the process. Before it begins, the glucose in your mitochondria gets converted into a substance called pyruvate or pyruvic acid, as well as a small amount of a substance called adenosine triphosphate. In the presence of oxygen, pyruvic acid gets converted to another substance, called acetyl coenzyme A. During the Krebs cycle, acetyl coenzyme A is broken down and its constituent atoms are used to generate more ATP, which your body uses as a main source of energy.
Significance
The conversion process that begins with carbohydrate consumption and leads to the Krebs cycle is responsible for the energy that powers almost all of the cells in your body, according to Teachers' Domain. When you eat foods that contain protein or fat, they also ultimately take part in this process. However, before your body can use proteins and fat for this purpose, the molecules inside them must be broken down in your liver and transformed into glucose.
Considerations
When your body has enough energy to meet its current needs, it stores your excess glucose supply in your liver as fat and a glucose derivative called glycogen. When your energy levels fall, glycogen and fat get reconverted into glucose, which enters your bloodstream and then your cells' interiors, where it plays its role in the process that leads to the Krebs cycle. However, if you don't take in enough oxygen, the Krebs cycle won't begin. Instead, your body will take the pyruvic acid in your cells and use it to make a substance called lactate or lactic acid.
References
- Teachers' Domain: Krebs Cycle
- Biology Online: Krebs Cycle
- Visionlearning.com: Carbohydrates; Anthony Carpi, Ph.D.; 2003
- Centers for Disease Control and Prevention: Nutrition for Everyone; Carbohydrates
- Biology Online: Pyruvic Acid
- "Scientific American": Why Does Lactic Acid Build Up in Muscles? And Why Does It Cause Soreness?; January 23, 2006
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