Microvilli - Distinction of Nutrients

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In summary, the human digestive system is complex and involves the absorption of various nutrients through the villi and microvilli in the small intestine. These structures are specific to certain nutrients and use a lock-and-key mechanism to transport them into the bloodstream. Vitamins and minerals are absorbed indirectly by attaching to fats and amino acids which then bind to sodium ions and enter the bloodstream. This process also explains why isolated minerals can be treated as toxins by the body and are only absorbed when hidden in other nutrients. The receptor sites in cell membranes on the villi work on molecules, not particles, and there can be competition for these sites. This is why taking large amounts of certain nutrients, such as vitamin C, can lead to deficiencies in other nutrients,
  • #1
I've been reading about the human digestive system and diving deeper into the details, however I can't seem to find a webpage that answers my questions. All my current knowledge can be summed by these two links:


The epithelium in the small intestine is lined by villi and microvilli which are responsible for transporting nutrients, fats, lipids, sugars, amino acids, etc. However, each microvilli is specific to the nutrient it absorbs. What I'd like to know is, how do enterocytes differentiate between various nutrients and target them? I know, as per the article, that vitamins and minerals are absorbed indirectly; they latch onto fats and amino acids, which in turn latch onto sodium ions, and ride through the enterocytes and into the bloodstream like a trojan horse.

Reading this, it seems to me that the body doesn't "see" the fats or the amino acids, it only detects sodium -which happens to bind to these nutrients and conveniently reel them in. Furthermore, isolated minerals are actually treated as toxins by the body, they are also "unseen" by our metabolism; the only reason we absorb these minerals is because they hide in other nutrients. They're like refugees hiding in the trunk of your car to cross the border.

My question:

How do fat-enterocytes identify fats while amino acid enterocytes identify and target each individual amino acid? Are minerals somehow filtered too? Or can an Fe particle latch onto any fat or amino acid and ride them into the bloodstream indiscriminately through it's vehicle's specific gate?
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  • #2
Receptor sites in cell membranes on the villi:
They work on molecules, not particles. There is a sort of lock-and-key mechanism - as an analogy.
Here is a technical explanation for glucose absorption by villi in the small intestine:

Note: - the exact same lock-and-key system may work well for several different nutrients. Example: Cu, Zn, and ascorbates (vitamin C ester) all are picked up by the same transporter. So there can be "competition" for given receptor site. Taking a vitamin C pill floods the intestine with lots of ascorbate, which means the relatively very few Cu bearing molecules present may never get a ride out even though it is on the correct binder molecule. This explains why taking lots of vitamin C long term can cause a copper deficiency.
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Related to Microvilli - Distinction of Nutrients

What are microvilli?

Microvilli are microscopic, finger-like projections found on the surface of cells. They are most commonly found in the lining of organs involved in absorption, such as the small intestine.

What is the function of microvilli?

The main function of microvilli is to increase the surface area of cells, allowing for more efficient absorption of nutrients and other substances. They also play a role in cell signaling and adhesion.

How do microvilli distinguish between nutrients?

Microvilli have specialized proteins on their surface that act as receptors for different nutrients. These receptors bind to specific molecules and trigger a series of events that allow for the absorption of those nutrients into the cell.

What happens when microvilli are damaged or destroyed?

If microvilli are damaged or destroyed, the surface area of the cell decreases, leading to a decrease in nutrient absorption. This can result in malnutrition and other health issues.

Can microvilli be regenerated?

Yes, microvilli can be regenerated if they are damaged. The cells that make up microvilli have the ability to divide and produce new microvilli. This process can be stimulated by certain growth factors and hormones in the body.

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