Minerals Flashcards
Folate (B9)
- precursor of tetrahydrofolate, coenzyme involved in generating precursors for DNA and protein synthesis
- hemopoietic B vitamin
Deficiency:
- neural tube defects in newborns of deficient mothers
- macrocytic anemia
- hyperhomocysteinemia (cardiovascular risk)
Suspectible:
- pregnancy
- elderly
- alcoholics
- patients with certain long term drug treatments
- people with genetic polymorphisms in folate metabolism
Folate supplementation
- inadequate folate early in pregnancy appears to be associated with neural tube defects. Mothers may have inadequate folate without symptoms
- demand very high in pregnancy and lactation
- grain products enriched in folate have lowered the risk
- defiency inhibits DNA synthesis by decreasing availability or purines and dTMP
- anticonvulsant drugs and oral contraceptives may also interfere with absorption of folates
Cobalamine (B12)
function:
- coenzyme in methionine synthesis and in conversion of methylmalonyl CoA to succinyl CoA
- needed in folate metabolism
- can be stored very effectively but deficiencies come from lack of absorption due to deficiency in intrinsic factor
Deficiency:
-pernicious anemia (megaloblastic anemia with demyelination)
Susceptible:
-elderly, patients with malabsorption diseases, long- term vegetarians
Megablastic anemia
- large size of RBCs in presence of folate/vitamin B12 deficiency
- arises from a deficiency in nucleotides, leading to decreased DNA and RNA synthesis. Cells increase in size without dividing, and large immature RBCs do not carry sufficient oxygen
- pernicious anemia refers specifically to a B12 deficent anemia arising from lack of intrinsic factor
Minerals
- inorganic compounds critical for human physiology
- many minerals are enzyme cofators, but they can also play structural roles in proteins or on their own
- categorized as macrominerals and microminerals based on level required (doesn’t correlate with importance)
- often work in parallel with vitamins, so supplements often contain both
Cobalamine and cobalt
- cobalamine contains a cobalt
- B12 in food must be released from protein by acid hydrolysis in the stomach. It then must bind to intrinsic factor to be absorbed in the ileum
Mineral classification
- Macrominerals:
- Potassium, Sodium, Chloride, Calcium, Phosphorus, Sulfur, Magnesium
- 100-200 mg/day
Microminerals:
- Iron, Copper, Zinc, Chromium, Iodine, Manganese, Selenium, Molybdenum, Fluoride, Boron
- lower 100 mg/day
Calcium
Function:
- major component of bone
- signaling
- coagulation
- muscle contractions
- neurotransmission
Deficiency:
mild- muscle cramps, osteoporosis
severe- rickets
Susceptible groups:
-children, adult women, elderly
Where does calcium come from and go?
- 98% of calcium is in bone and teeth
- hydroxyapatite is the basic mineral component of bones and teeth
- bone is the body’s calcium reservoir: bone releases Ca2+ if serum levels of insufficient
- 2% of calcium in rest of the body
- low serum calcium signals enhance intestinal absorption and stimulate bone resorption
Osteoporosis
- osteoporotic bone from calcium deficiency is porous
- calcium intake during period when bone is reaching maximum density (age 10-35) is important to prevent osteoporosis
- even higher levels of calcium intake are required to maintain bone mass in postmenopausal women (exercise also helps main bone density)
Magnesium
Functions:
- essential for many enzymes useing MgATP as substrate (usually transporters)
- present at high levels in bone
Deficiency:
-weakness, tremors, cardiac arrhythmia
Susceptible groups:
-alcoholics, patients taking diuretics or experiences severe vomiting and diarrhea
Phosphorus
Functions:
- most present in phosphates
- Major component of bone (hydroxyapatite)
- constituent of nucleic acids, membrane lipids
- required in all energy-producing reactions
Deficiency:
rare- can result in rickets, muscle weakness and breakdown, seizure
-quite abundant in food supply
Iron
Function
- O2/CO2 transport in hemoglobin
- oxidative phosphorylation
- cofactor in several nonheme iron proteins and cytochromes (redox properties of iron are important
- best sources are meat, dried legumes and fruit and iron enriched cereal products
Defiency:
-microcytic hypchromic anemia, decreased immunity
Susceptible:
-common in children and menstruating women, pregnant women, and elderly
Iron absorption and distribution
- reduction of Fe3+ and Fe2+ is promoted by vitamin C in diet (Vitamin C deficiency causes mild anemia)
- Low pH in stomach helps release Fe3+ from ligands and make it bioavailable
- uptake of iron in mucosal cells of small intestine is regulated in response to iron-deficient or overload states
- iron is carefully escorted both in circulation and in cells because of the potential for inadvertent redox damage
Major barriers to absorption
1) release of Fe3+ from food
2) availability of reducing agent to convert Fe3+ to Fe 2_
- although spinach does contain iron, it is so tightly chelated that it cannot be readily absorbed.
- the second requirement is often satisfied by vitamin C
-hepidin signals iron sufficiency and prevents export of Fe2+ from duodenal mucosal cell by downregulating the exporter
