Glucose, Where Does It Come From, How We Use It, Store It and Recycle It
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Posted: Saturday, May 08, 2010
by Samantha Mendoza
Lifetime Fitness Nutrition
Glucose gives us "gasoline" for living. It is a single molecule used in animals and plants. We also know it as blood sugar or dextrose.
When you eat food containing single carbohydrates like: fructose, glucose or galactose, you absorb them directly into your capillary, but when you eat disaccharides or polysaccharides, you must digest them first, with special enzymes that work like a scissor, making them available for your needs.
1) Fiber, starch, monosaccharides and disaccharides enter the stomach and pass into the small intestine. Some of the starch partially breaks down.
2) An enzyme found in the pancreas, digests most of the starch and dissacharides.
3) Enzymes on the surface of intestinal wall cells split disaccharides to monosaccharides.
4) Monosaccharides enter capillary, then are delivered to liver via the portal vein.
5) This body's lab converts galactose and fructose to the final most used molecule we're talking about.
6) Finally, fiber travels without changes to the colon.
How do we use it?
We should all know that carbohydrates are essential, there is no substitute for them, that is why we can't take them out of our diet (no carbs diets are wrong).
Glucose can be converted into body fat, but not the other way around. This is the reason why fasting and low carbohydrate diets are dangerous. A severe carbohydrate deficit can produce two problems:
1) Without this molecule, body will turn to protein, diverting protein from critical functions.
2) Fat fragmens have to combine with carbs before they can be used for energy. Using fat without carbs causes your body to go into ketosis (unusual products of fat breakdown called ketone bodies accumulate in the circulatory system, disturbing the normal acid-base balance.
Ketosis can be dangerous for the baby during pregnancy, being able to cause irreversible mental retardation after birth.
The minimum amount of carbohydrates needed to avoid protein sparing action and ketosis is about 100 grs/day for an average size person. 3-4 Times this minimum is most recommended and you can cover it with your 5-10 vegetables, fruits and grains.
How do we store it?
Let's say you ate. Your level of glucose in the blood rises. The pancreas responds releasing a hormone called insulin. This signal will induce muscle and liver cells to use some of the glucose to build a polysaccharide called: glycogen (like a reserve of energy for 4-6 hours of fast.
Muscle appropiates 2/3 of the body's total glycogen. The liver stores the other 1/3 and is more generous, by making it available as dextrose for the brain or other organs when you run out of supply.
When dextrose concentration drops and cells need energy, a pancreatic hormone called: glucagon floods the bloodstream. Glycogen starts breaking into small units of your favorite "gasoline" molecule and then, you can continue working.
How we return it to the bloodstream?
Have you sometime felt dizzy or weak? Probably you're working with the reserve.
Have you become confused or with difficulty for breathing? Then, you have probable raised high levels of dextrose. And guess what, either one or the other condition is regulated in order to balance your levels to adequate in your body.
You depend on two safeguards:
1) Your glycogen stores (remember the liver is the one who shares) or, 2) Diverting excess of glucose into the muscles and the liver liver to convert it into glycogen or even fat (by the liver only).
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Remember, if you're running low, glucagon will be released and glycogen will break into small usable units. Another hormone, epinephrine, will also break liver glycogen as part of a defense mechanism in times of danger or stress situations. Good thing!
How glucose is affected by the duration of the activity?
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