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Biochem 2.1 - PCC
Water Soluble Vitamins
| Question | Answer |
|---|---|
| Is digestion necessary for vitamin C? | No |
| How is vitamin C absorbed? | Ascorbic acid is absorbed via sodium dependent active transport in the small intestine and dehydroascorbic acid is aborbed via facilititaed diffusion via niacin but is quickly reduced back to ascorbic acid in enterocytes. |
| Is absorption of vitamin C directly or inversibly proportional to cnsumption? | It is inversibly proportional. The more you consume, the less is absorbed. |
| What can else can influence the absorption of vitamin C? | 1. Glucose 2. Large doses of iron |
| How is vitamin C transported? | In the plasma through the blood stream |
| Does folic acid need to be digested? | No |
| What amino acid is attached to folic acid? | Glutamic acid |
| Where does the glutamic acid get's stripped off and by what? | The residue is removed by conjugase (Zn-dependent enzyme) in the brush border |
| What type of absoprtion occurs with folic acid? | It is absorbed by active transport (food) or by passive diffusion (oral doses) in the small intestine. |
| What are the carriers of folic acid? | 1. Folate binding proteins (FBP) 2. Reduced folate transporter (RFT) |
| What is the reduced form of folate and where does it occur? | In the enterocytes, it is reduced to tetrahydrofolate then it is methylated ti 5-methyl THF |
| Where is the protein bound B12 released? | Stomach |
| What stimulates the relase of B12 in the stomach? | Pepsin and HCL |
| What does free B12 bind to? | R proteins from saliva and gastric juices |
| What does B12 bind to in the stomach? | Intrinsic factor |
| How is B12 absorbed? | IF receptors in ileum bind B12-IF complex and absorb it by endocytosis |
| How is B12 transported in the blood? | Transcobalamins |
| Can B12 be sotred in the body? | Yes! Only water soluble vitamin to have this feature. |
| What is zollinger-Ellison Syndrome? | Increased production of stomach acid causes the SI pH to drecrease to 4.2. Optimal pH for SI proteases to hydrolyze the vitamin B12-R protein complex is around 5.5. Therefore very little or no absorption. |
| Where can you find vitamin B12? | Aminal products: meat, milk, eggs, fish |
| What is spirulina? | Group of blue algae |
Created by:
LrB
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