HNF 462Exam # 3 Study Guide Lectures: 22-28 Lectures 22 and 23Iron, Zinc, and Copper1. How does iron status regulate iron absorption?a. Iron regulation starts in the intestinal cells, where it is stored before being absorbed b. If iron status in the body is low, iron absorption will be initiatedc. If iron status in the body is sufficient, iron absorption will not occur, and the iron will instead be excreted from the body2. How does heme iron absorption compare to non-heme iron absorption? Do they use the same transporter? What are the transporters? For the non-heme iron, what form is better absorbed?a. Heme iron absorption:i. Better absorbed than non-heme ironii. Heme transporter protein expressed in the intestinal microvilli: releases iron inside of the cell for storage (stored in mucosal ferritin) b. Non-heme iron absorption:i. Ferric iron (Fe3+) is converted to ferrous iron (Fe2+) in the intestinal lumen; ferrous iron is transported into the intestinal cell by DMT1 protein for storageinside the cell (stored in mucosal ferritin)c. Use different transportersi. Heme: Heme transporter protein ii. Ferrous form: DMT1d. Both forms of iron:i. Transported into blood by ferroportin1 proteinii. If the body is iron sufficient, hepcidin will inhibit iron absorption by degradingferroportin 3. Identify the enhancers and inhibitors of non-heme absorptiona. Enhancers:i. MFP factor: associated with meat, fish and protein; promotes non-heme iron absorptionii. Ascorbic acid (vitamin C): enhances non-heme iron absorption if eaten at the same mealb. Inhibitorsi. Phytates and fibersii. Calcium and phosphorusiii. EDTA in food additivesiv. Tannic acidv. Polyphenolsvi. Oxalates4. How do Zn and Fe influence each other’s absorption?a. High zinc concentrations cause low Fe absorptioni. Zinc binds with transferrinb. High iron intakes cause low Zn absorption5. What’s the function of metallothionein in zinc homeostasis?a. Metallothionein stores zinc inside the intestinal cellsb. When cells need more zinc, metallothionein will be degraded c. Regulates Zn homeostasis by providing a defense against too much absorption into the body6. What protein transfers iron in the blood? What form of iron does it bind to? How is iron transported by this protein taken up by cells?a. Transferrin carries iron in the bloodb. Binds to ferric (Fe3+) ironc. Iron is taken up by cells from the blood by receptor-mediated endocytosis: transferrin bound to iron binds to a transferrin receptor on the cell membrane, and isthen taken in by the cell via endocytosis7. What protein stores iron inside of cells?a. Mucosal ferritin stores iron inside cells 8. How does iron status regulate the amount of ferritin and transferrin receptor? By what mechanisms?a. Low iron status: reduced ferritin levels and increased transferrin levelsi. Three iron atoms bind to mRNA sequence to suppress translation of ferritinii. Three iron atoms bind to mRNA sequence to increase translation of transferrin receptorsb. High iron status: increased ferritin levels and decreased transferrin levelsi. Four iron atoms bind to mRNA sequence and increases translation of ferritinii. Four iron atoms bind to mRNA sequence and suppresses translation of transferrin9. What organs store iron in the body?a. Note: this regulation is a good example of a nutrient regulating gene expression at the mRNA level as opposed to at the transcriptional level like vitamin D and A do.b. Liverc. Bone marrow: formation/maturation of RBCsd. Spleen: RBCs recycled10. What are the commonly used methods to determine iron status?a. Measure serum ferritin and transferrin receptorsb. Measure of transferrin saturation c. Measure erythrocyte porphyrin (a precursor to hemoglobin that accumulates in the plasma)d. Measure hemoglobin and hematocrit values (volume of RBCs)11. Generally, what are the functions of iron in the body? What are the functions of zinc in the body?a. Functions of ironi. Oxidation-reduction reactions of energy metabolism1. Cofactor to enzymes that control brain function, tissue formation, immune function, and hormone production2. Part of the electron carriers in ETCii. Structural/functional component of hemoglobin and myoglobin1. Carries oxygenb. Functions of zinci. DNA/RNA synthesis (cell division)ii. Manufactures hemeiii. Essential fatty acid metabolismiv. Releases vitamin A from liver storesv. Metabolizes alcohol in livervi. Antioxidantvii. Needed for the action of insulin/thyroid hormoneviii. Blood clotting/wound healing12. What are metalloenzymes?- Enzymes that have metals attached to them- Important function of minerals is to form these enzymes13. What are the major causes of iron deficiency?a. Low intake of bioavailable ironb. Increased iron requirements due to rapid growth, pregnancy, and menstruationc. Excess blood loss14. List a few main symptoms of iron deficiencya. Severe iron deficiency can cause anemiab. Impaired cognitive functions and immune functionc. Reduced work capacity d. Fatigue, weakness, headaches, apathye. Inability to regulate temperaturef. Pica: craving for nonfood substances15. Is the iron RDA the same between men and women? Why?a. Iron RDA for women (18mg/day) is higher than for men (8mg/day)b. Iron is stored differently in men than in womenc. Women’s menstrual cycleLecture 24Zinc and Immune Functions16. What is a zinc finger? What important function do zinc fingers have?a. A folding of peptides in which zinc is bound to the middle b. Contains 2 cysteines and 2 histidines, which hold zinc in placec. Important for the function of transcription factors—can inhibit or initiate DNA transcription17. Know that in zinc deficiency, less important zinc-proteins are degraded? Why?a. Degradation of less important zinc-containing proteins (not necessarily critical for proper body function) in order to release zinc into the system so that it can travel to other proteins where it is needed moreb. The body will also sacrifice the adaptive system (more potent line of immune defense) in order to conserve the innate system (first line of immune defense).18. As a general concept, understand some nutrients’ availability in plants is determined by their soil content. This applies to zinc, selenium, iodine, and others.a. Soil content affects the nutritional status of plants for some nutrients b. Zinc, selenium, iodine deficiencies can be common in some parts of the world if the soil is deficient of themLecture 25Selenium19. Know the metabolism of selenium; how is