Digestion and Absorption of Carbohydrates, September 18, 2015
In order to learn about nutrition in the body, we need to know about all the different metabolic processes. One can ask the questions, “Is sugar bad for you? If so, why?” As we will find out, these are very complex questions. And we need to know how glucose is handled by the body in order to even come close to answering these questions. Today’s lecture involved a blackboard demonstration of carbohydrate digestion and glucose absorption. I spent a great deal of time on this, but I thought it was important to go through it in detail.
Digestion- What is interesting to me is that both amylose and amylopectin are digested so fast—see their glycemic indices. However, there are versions of amylose that are very long that are more slowly digested because the chain curls up on itself and the enzyme can’t get at it.
Also in the diagram is cellulose, which looks very similar to amylose (long chain of glucose molecules) but if you look closer it uses a different kind of bond (called Beta) that links the glucoses together and human enzymes can not cleave it.
Sucrose is only a disaccharide and it is only half glucose. The other half is fructose.
No matter what, the glucose transporter in the enterocyte requires sodium and there is co-transport of glucose and sodium into the enterocyte cell. Then the glucose enters the blood and flows fairly directly to the liver. The increase in glucose in blood stimulates the secretion of insulin from the pancreas. Insulin is important in removing glucose from the blood. We will go over this in great detail in the next lecture.
Here are some of the figures.
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