1Metabolism 2 Study Guide 2Zinc1. What is the RDA and where is it found?- The RDA for zinc in men is 8 mg/day and in women it is 18 mg/day.- It is found in seafood, meats, eggs and dairy, whole grains and in vegetables. It can also be in theendogenous form of carboxypeptidase.2. Absorption and transport.- Like all other food, zinc has to by hydrolyzed out of the food in digestion with HCl. Once hydrolyzed, it is absorbed in the jejunum best at around 12-60%. Before absorption, zinc has to bind to a protein called metallothionein—this does not serve as a transporter, but more as a zinc pool. This is required. Animal products are absorbed best.- The two transporters are called Nramp2 and DC/MT1.- Phytate, fiber, and oxalates decrease the absorption of it. There are many interactions with other minerals for zinc: calcium decreases its absorption at high does, iron decreases it, and so does copper. The reason will be gone over in the copper section. - Citric acid increases the absorption rate, since an acidic environment will help hydrolyze the zinc faster, so it is available faster to absorb. Amino acids also enhance the absorbtion- Once it is in the enterocyte, it can either be used there, stored there or transported elsewhere.If stored there, it is stored with metallothionein, if transported out, then four different transporters can be used. ZnT-1 through ZnT-4. 3. Functions- Zinc is a catalytic, structural, and regulatory mineral. As a catalyst, it is involved in many reactions: most notably the carbonic anhydrase in respiration (Co2 + H2o H+ + HCO3) and with alkaline phosphatase. It is used with Tony Berardi1alcohol dehydrogenase, superoxide dismutase, and as carboxypeptidase in protein digestion. Structurally it stabilizes the membranes of the cell and help in the folding of polypeptides into functional proteins and for tissue growth and bone formation, along with immunity. It has various roles in carbohydrate metabolism, BMR, taste, and other transporter proteins. Regulatory is it has a role in gene expression. 4. What are some nutrient interactions that it has?- There are many interactions with other minerals for zinc: calcium decreases its absorption at high doses, iron decreases it, and so does copper. The reason will be gone over in the copper section. 5. DeficiencyThere are two levels of deficiency:• Mild deficiency has 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. Know the differences, like with dwarfism and hypogonadism. • Acrodermatitis Enteropathica is an inherited disease where the body does not produce the enzyme to shuttle zinc across the intestine. It is treated with large oral doses, because some will still leak in, despite the lack of the enzyme.• Everyone who is at risk for deficiency should be common sense: alcoholics are at risk for every deficiency, and any one where getting nutrients will be a problem: burn patient, those on TPN (tube feeding) surgery. 6. Toxicity• It is rare, but it does occur when food is prepared in galvanized containers or when zinc is inhaled. Very high doses will interfere with iron and copper metabolism and therefore lead to anemia. The patient will present nausea, vomiting, and cramps.7. How to assess status. Tony Berardi1• A WBC test is the best to assess the zinc status. For functional tests, we have a light-dark test, taste acuity, and a zinc tolerance. It might be best to use a combo of serum zinc and the metallothionen—as it will decrease when deficient. Remember that this is that zinc pool.Copper1. What is the RDA and where is it found?- The RDA is 900 ug/day for both men and women and it found in organ meats, legumes, nuts, and seeds. It is in the body as two forms, Cu+ (cuprous) Cu++ (cupri) 2. How is it absorbed and transported? • Range from 12% to 50% depending on intake (if you need a lot, your body will absorb more). With a low intake, it will be absorbed active transport (taking energy) and a high intake will make it passive transport. Think of the concentration gradient: If you are trying to absorb a small amount, you must have a larger amount in your body, so it will have to move against its concentration gradient. And as usual, it has to be freed from the proteins via HCl and proteases.• Now to things that inhibit it: Zinc. The reason for this is because, as we know, zinc needs to bind to the metallothionein (shown as MT) first, but copper has a higher affinity to it for some reason. Sothe copper will displace the zinc from the MT, and get “trapped” in it. If are zinc intake is higher than the RDA, it will make more MT as a result: more MT means more copper will bind to it and notbe absorbed.• Sulfur, fiber, vitamin C, and phytates also inhibit it Once in the blood, copper travels on the proteins albumin and transcuprein. It is excreted via bile through the intestine. Somewhat in sweat. 3. What are the functions?• Copper acts oxidize ferric to ferrous. Going back to iron, iron has two forms: ferric (iron++) and ferrous (iron+++). It is readily absorbed as ferric, but it can only bind to transferrin to travel in the body as ferrous; so it must be oxidized. Copper picks up an electron from the ferric, oxidizing it to ferrous. This is why a copper deficiency will lead to anemia: copper is required for iron function. It does this through the enzyme ceruloplasmin.Tony Berardi1- Superoxide dismutase depends on copper also, along with amine oxidases, cytochrome C oxidase and tyrosine metabolism. It is connected to immune and nervous function and gene expression. - Its other functions are in various oxidases that act as either free radicals or catabolizes neurotransmitters.4. Is there a deficiency with copper and how can you assess it?- You can simply look at ones plasma levels or their serum ceruloplasmin to assess status. - Deficiency is rare, but it will cause hypochromatic anemia, a lowered immune function, osteopenia and myocardial diseases.- Wilson’s disease is a genetic disease that leads to copper excess with impaired excretion. It is caused by a mutation in the ATP 7B gene.5. Toxicity- Is rare, with 200x normal intake, and retarded people that eat pennies. It will lead to nausea, liver and kidney disease. Iron1. What is Iron and where is it stored?- When you think of iron, think of hemoglobin and oxygen transport.
View Full Document
Unlocking...