This is part 1 of a 3-part series about how the three macronutrients (carbohydrates – proteins – fats) are absorbed by the body. Here I explain how digestive enzymes break down food and how the intestines take up nutrients into the body. The textbook ‘Medical Physiology’ 2nd edition by Boron & Boulpaep is the source of this information.
BB005 – Carbohydrate digestion Basics
The challenge of this series is to create complete figures that do not require much or any additional explanation. All essential info is listed in the figure itself in small text boxes. Interesting trivia or more detailed explanations are put in the blog post.
This is an overview of the different types of sugars commonly found in food and a legend of the schematic depictions thereof in the following figures.
Complex carbohydrates are mainly starches from plants and glycogen from animal meat. They are long carbohydrate chains (much longer than depicted here). Depending on the source, they can contain a million carbohydrate rings.
The prefix ‘oligo-‘ is use to indicate ‘a few’ (I am not sure what the exact definition is in this context). The ‘mono-‘ prefix means ‘one’, so a monosaccharide indicates a single carbohydrate ring. Complex carbohydrates are also called polysaccharides, where ‘poly-‘ means ‘many / a lot’.
The enzymes are named after the disaccharide (2 carbohydrate chains) they are able to cut. Lactase cuts lactose (milk sugar), which is made out of glucose and galactose. Sucrase cuts sucrose (table sugar), which is made out of glucose and fructose.
The use of sodium to improve the function of transporters is used in a lot of ways in the body, also for other transporters of other cell types.
BTW: the transporter that exchanges sodium and potassium (Na-K exchanger) is needed to empty the cell of sodium, so it can be used to facilitate the uptake of glucose from the intestinal lumen. Of course, there are many other transporters used by intestinal epithelial cells, but I will keep things simple here ;).
Part 2 of this series will be about proteins. In part 3 I will discuss fats.