Metabolism 2 Study guide Exam 21. Explain the DRI. The goal of the DRI is to prevent chronic diseases, not to prevent defiencys. The focus is now on malnutrition from over nutrition. DRI started in 1835 with lemons on ships. Then first RDA was in 1949 with the focus to prevent defiency in the military. Changed because it was too broad (focus on healthy people, and too many fat unhealthy people). Now have EAR, RDA, AI, and UP. 2. What are vitamins and difference between fat and water soluble? They are micronutrients that must be supplied from the diet. Needed for normal function and their absence cause certain symptoms with each one. The body can make some, but not in appreciable amounts. Fat soluble is obviously soluble in fat, stored in the body in large amounts so it’s not required every day. Since it’s stored, defiency takes a long time to occur. Most have precursors, and only higher organisms need them. Can be toxic at low amounts (but still way higher than the UL). Water soluble arestored minimally, excreted in the urine, so defiency can happen much faster. Absorbed into blood, sincewater soluble and both simple and complex organisms need. Since they aren’t really stored, they are only toxic at mega doses (100x DRI)Folate1. What is the synthesis? It’s made from 9 different precursors, such as PABA, glutamic acide, Pterdine. The body can make all, except Pterdine acid.2. How is it absorbed? It must be absorbed as a monoglutamate form, so the polyglutamate is hydrolyzed with a conjugase. The conjugase is also Zinc dependent, so you need Zinc to absorb Folic acid. Some foods have conjugaseinhibitors though, like oranges cabbage, lentin. Then it is reduced in the liver to its active form, THF. Minimal storage of 11-28 mg.3. What are the functions? It is use in one carbon transfers, in the synthesis of the purines and pyridimes (Nucleic acids) and in some AA metabolism, such as the glycine-serin, but the important one is the methionine regeneration.4. What are the sources? Green, leafy veggies, oranges, yeast. It is destroyed with cooking, 50-95%5. What is the defiency? The risk groups are those that prolonging the cooking. Alcoholics, pregnant and lactating women are also at risk. And some intestinal diseases, such as Celiac disease. Some drugs also interfere with the absorption, such as methotrexate in chemo, some antimicrobials, and Dilantin, an anticonvulsant. The defiency causes megaloblastic RBC (large and immature) 6. How to assess and what is the DRI? There are 2 ways: You can check the RBC folate level, but this only shows long term. You can check the plasma folate levels, it will be as 5-methyl THF. The DRI is 400 ug, and 600 ug in pregnant women. Expressed in DFE= 1ug folate + 1.7ug synthetic folate, and synthetic has better bioavailability. Also learnthe whole Folate-Cobalamin-Methionine reaction!Cobalamin1. What is its active form? They forms are also known as corrinoids, and they are multiple forms. They all has 4 rings surrounding the cobalamin. The two active forms are 5-deoxyadenosylcobalamin, which has 4 deoxys, and methylcobalamin, which has 4 methyls. All the other forms can also be converted into these.2. How is it absorbed? This vitamin has the most complicated absorption. So first the pepsin releases the cobalamin from its ring, and the cobalamin bounds to an “R” protein, and then travels to the small intestine. In the first part, the duodenum, the “R” protein is hydrolyzed and then the cobalamin binds then something called Intrinsic Factor, which is made in the stomach. Now it gets absorbed in the ileum, where the receptors are. Once the cobalamin is in the blood, it then binds to either Transcobalmin 1,2, or 3. (Although 2 is the most common one) And then it is stored in the liver mostly and some in the muscles. Stored better than most water soluble vitamins, so defiency take several years to occur. Bacteria in the intestinal also can make a little3. What are the functions? Works with folate in that whole methione reaction. Also in DNA synthesis, and myelin synthesis for the neurons. 4. What is the defiency? It rarely occurs in the diet, mostly in some absorption problem. This is easy to see when you look at how many molecules are involved in its absorption. Those that can’t make the Intrinsic Factor, since as patients with gastrectomys, or impaired mucosa are at risk. Or they have a lower surface area for absorption, with a blind loop, or ilealitis. Pancreatis and parasites don’t help either. Of coursealcoholics and elderly also. Defiency always occurs in stages. So first you get low serum Trancoblamin 2levels. Then you get low RBC levels. Then you get lower DNA synthesis, greater homocysteine levels (these are bad), Anemia, and neuropathy. And finally you get Pernicious Anemia, which is characterized by appearance of megaloblastic RBC’s, and GI abnormalities.5. What are the sources? Animal in animal products! About 30% is destroyed in cooking.6. What is the DRI? It is 2.4-2.6 ug dailyZinc1. Main properties- Most of the Zinc is in the muscles and bone, but it is not available there. It is a catalytic,structural, and regulatory mineral.2. Absorption and transport.- Needs to be hydrolyzed obviously, and animal sources (oysters are the best) are better absorbed. It enters the brush border and then the cytosol, then binds to metallothionein (Zinc pool)- To enhance: If deficient (like all nutritients) Pregnant, lactating Human milk better absorption.- To inhibit: Phytate, oxalate, fiber High dose of Ca Fe if supplemented Cu supplementation- Excreted In poop3. Functions- Catalytic Lots of enzymes, such as carbonic anhydrase in acid-base balance, DNA polymerase. - Structural It stabilizes biomembranes, and helps proteins fold up.- Regulatory Gene expression, stimulator of the trans-acting factors.4. Deficiency- Mild is slower growth, impaired immune function and wound healing, dermatitis, sore throat. Severe is all of the above and anorexia (from loss of taste), dwarfism, hypogonadism, and night blindness- Acrodermatitis Enteropathica is an inherited disease where the body does not produce the enzyme to shuttle zinc across the intestine. Treated with large oral doses, cause some will leak in5. Toxicity- It is rare, but it does occur when food is prepared in galvanized containers or when
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