Water Soluble Vitamins

Liquid-soluble vitamins are transported across the plasma membrane through various processes involving specific transport mechanisms. Here are some examples of organs and processes for transporting liquid-soluble vitamins:

1. Vitamin C (Ascorbic Acid):

• Organ: Small intestine (where most vitamin absorption occurs)

• Transport Process: Active transport and facilitated diffusion

• Mechanism: Vitamin C is transported into the intestinal epithelial cells via specific transporters like the sodium-dependent vitamin C transporter1

2. Vitamin B1 (Thiamine):

• Organ: Small intestine

• Transport Process: Active transport

• Mechanism: Thiamine is transported into the intestinal epithelial cells through a specific sodium-dependent multivitamin transporter located on the apical side of the cells. From there, it can be transferred to the bloodstream and delivered to various tissues.

3. Vitamin B2 (Riboflavin):

• Organ: Small intestine

• Transport Process: Passive diffusion and carrier-mediated transport

• Mechanism: Riboflavin can cross the intestinal membrane via passive diffusion, but it can also be taken up by specific carriers like the riboflavin transporter 2 to enhance its absorption.

4. Vitamin B3 (Niacin):

• Organ: Small intestine

• Transport Process: Passive diffusion and carrier-mediated transport

• Mechanism: Niacin can passively diffuse across the intestinal membrane, but it can also be taken up through specific transporters like sodium-dependent multivitamin transporter and proton-coupled high-affinity niacin transporter 1.

5. Vitamin B5 (Pantothenic Acid):

• Organ: Small intestine

• Transport Process: Active transport and passive diffusion

• Mechanism: Pantothenic acid is taken up into the intestinal cells through a specific sodium-dependent carrier and passive diffusion. It then enters the bloodstream for distribution.

6. Biotin (Vitamin B7):

• Organ: Small intestine

• Transport Process: Active transport

• Mechanism: Biotin is transported across the intestinal membrane via a sodium-dependent multivitamin transporter (SMVT).

7. Vitamin B9 (Folate):

• Organ: Small intestine and liver

• Transport Process: Active transport and carrier-mediated diffusion

• Mechanism: Folate is taken up by intestinal cells through a proton-coupled folate transporter (PCFT) and then exported into the bloodstream. In the liver, folate is stored in the form of polyglutamates.

These examples demonstrate how different liquid-soluble vitamins utilize specific transporters and mechanisms to be absorbed and transported across the plasma membrane in various organs.