7. Minerals Flashcards
What are minerals? Structural characteristics?
Chemical elements that cannot be formed by the body, but are required in the diet
- inorganic (no carbon)
- carry a (+) or (-) charge
What do combinations of minerals yield?
Salts
How are minerals classified?
By amount needed per day
What are the metabolic functions of minerals?
- Enzyme cofactors –> energy production
- Electrical conductivity –> cell communication
- Electrolytes –> fluid balance
- Protein structure –>bone and teeth health
- Electron carriers –> oxygen transport
List the major minerals
Ca, Mg, P, Na, K, Cl
List the trace minerals.
Fe, Zn, Cu, Cr, Mn, Mo, Se, I
Describe the digestion of minerals.
Many minerals in the diet are bound to proteins –> protein digestion in the stomach by HCl and pepsin are necessary to release the minerals from the proteins they’re bound to
What is mineral absorption regulated by?
Regulated by proteins in the enterocytes of our small intestines
In what forms are minerals generally transported?
- Free form
- Complexed w/ other minerals (sulfate, phosphate, citrate)
- Attached to protein carriers (albumin)
What is the main protein of the human blood plasma?
Albumin
What is the function of albumin?
Binds water, cations (like Ca2+, Na+, and K+), fatty acids, and hormones
What are the common sources of calcium?
- Dairy
- Seafood w/ bones
- Some veggies (greens)
- Fortified foods
- Supplements
What is the adequate intake of calcium?
- 19-50 years old = 1000 mg/day
- 51+ years old = 1200 mg/day
What are the 2 main process by which calcium is absorbed?
- Carrier-mediated active transport
2. Paracellular diffusion
What is carrier-mediated active transport? Where does it occur? What is it regulated by?
- Ca2+ transported across cell by carrier
- Main transport occurs in duodenum and proximal jejunum
- Saturable
- Requires energy
- Regulated by calcitriol (active vitamin D)
What is paracellular diffusion? Where does it occur?
- Ca2+ gets in b/t enterocytes and into circulation
- Passive
- Nonsaturable
- In small intestine, but mostly in jejunum and ileum
- Requires no carrier
List substances that enhance calcium absorption.
- Vitamin D
- Sugars and sugar alcohols
- Protein
List substances that inhibit calcium absorption?
- Fiber
- Phytic acid
- Oxalic acid
- Excessive divalent cations (have same charge)
- Unabsorbed FAs
When is parathyroid hormone released? Function?
- When blood Ca2+ is low
- Increase osteoclasts to break down bone and release Ca2+ into the blood
- Increases Ca2+ reabsorption
What substances regulate extracellular calcium concentration?
- Parathyroid hormone (PTH)
- Calcitriol
- Calcitonin
How does PTH affect serum calcium and bone calcium?
- Increases serum calcium
- Decreases bone calcium
How does calcitriol affect serum calcium and bone calcium?
- Increases serum calcium
- Not much effect on bone calcium
How does calcitonin affect serum calcium and bone calcium?
- Decreases serum calcium
- Increases bone calcium
Cortical vs. trabecular bone. Significance?
- More metabolically active than cortical bone
- More prone to bone loss
What are the functions of calcium?
- Bone mineralization
- Blood clotting
- Nerve conduction
- Muscle contraction
- Enzyme regulation
- Membrane permeability
What are the consequences of calcium deficiency?
- Rickets (poor bone mineralization in children) w/ a co-deficiency of vitamin D
- Increased risk of osteoporosis (poor bone mass in adults)
- Hypertension, colon cancer, obesity
What are the consequences of calcium toxicity?
Kidney stones
What are the common sources of phosphorus?
- Meat, poultry, fish
- Eggs
- Dairy
- Cola type soft drinks
- Supplements
What is the RDA of phosphorus?
700 mg/day
How is phosphorous digested?
Hydrolyzed (cleaved from the organic compound it’s bound to) into inorganic phosphate
What are the 2 processes by which phosphorus is absorbed?
- Saturable, carrier-mediated active transport
- Diffusion
What substances enhance phosphorous absorption?
- Calcitriol
- Vitamin D
What substances inhibit phosphorous absorption?
- Phytic acid
- Excessive Mg, Al, Ca
What are the functions of phosphorus?
- Bone mineralization
- Nucleotide/nucleoside phosphates (structure, energy storage and transfer, intracellular second messenger)
- Phosphoproteins and phosphorylated forms of vitamins
- Phospholipids
What substances influence phosphorus balance in the body?
- PTH
- Calcitriol
- Calcitonin
What is the significance of the phosphorylation of proteins or vitamins?
Will usually activate or inactivate the protein and vitamin –> affects its functional abilities
What are the consequences of phosphorous toxicity?
Heavy cola drinkers may be at risk for kidney probs and low bone mineral density
What are the common sources of magnesium?
- Nuts, legumes, whole grains
- Coffee, tea, cocoa
- Supplements
What is the RDA of magnesium?
- 19-30 years old = 310-400 mg/day
- 31+ years old = 320 - 420 mg/day
What are the 2 mechanisms by which magnesium is absorbed? At what concentrations does each operate?
- Saturable, carrier-mediated active transport operates w/ low Mg intake
- Simple diffusion operates w/ higher Mg intakes
What % of Mg is transported in its free form? Bound to protein? Complexed w/ (-) charged ions?
- 50-55% in free form
- 33% bound to protein
- 13% complexed w/ (-) charged ions
In what forms is Mg transported?
- Free form
- Bound to protein (albumin or globulin)
- Complexed w/ (-) charged ions
What substances enhance Mg absorption?
- Vitamin D
- Protein
- Carbs
- Fructose
- Oligosaccharides
What substances inhibit Mg absorption?
- Phytic acid
- Fiber
- Excessive unabsorbed FAs
What are the functions of Mg?
- Bone lattice and surface
- > 300 enzyme rxns as structural cofactors or allosteric activator
- Interactions w/ other nutrients
What conditions increase risk of Mg deficiency?
- Malabsorptive disorders
- Excessive alcohol or diuretic use
- Parathyroid disease
- Burns
What conditions increases the risk of Mg toxicity?
Impaired renal function
What are the consequences of Mg toxicity?
Excessive intake of Mg salts may lead to diarrhea and dehydration
What are the common sources of iron?
- Heme iron (meat, fish, poultry)
- Non-heme iron (nuts, fruits, veggies, grains, tofu)
- Grain foods fortified w/ iron
- Supplements
What is the RDA of iron for men vs. women?
- Men = 8 mg/day
- Women = 8-18 mg/day
Why do premenopausal women need more iron than postmenopausal women?
Iron is lost when blood is lost –> need twice as much iron
How is heme iron digested?
Hydrolyzed from hemoglobin/myoglobin in stomach and small intestine
How is heme iron absorbed?
- Absorbed intact by heme carrier protein 1 (HCP1)
- Hydrolyzed to inorganic ferrous iron and protoporphyrin to be stored
How is non-heme iron digested and absorbed?
- Hydrolyzed in the GI tract by gastric secretions
- Ferric (Fe3+) reduced to ferrous (Fe2+) iron, which remains fairly soluble
- Ferrous iron passes into small intestine via DMT1
What is the main transporter of ferrous iron?
Divalent cation metal transporter 1 (DMT1)
What affects the synthesis of DMT1?
Iron status: more iron in system –> less transporter you make (and vice versa)
What is the effect of hephaestin on iron?
When Fe2+ comes into contact w/ it, it it oxidized back to Fe3+
What is the primary storage form of iron in the cells?
Ferritin
In what form is iron stored and transported?
In the less active ferric (Fe3+) form
What is the transport form of iron?
Transferin-Fe3+
What substances enhance Fe absorption?
- Acids (ascorbic, citric, lactic, tartaric)
- Meat, poultry, fish
What substances inhibit Fe absorption?
- Oxalic acid
- Phytates
- Polyphenols
- Ca
- Zn
- Mn
What are the characteristics of free Fe2+?
- Very reactive
- Can generate harmful free radicals?
How much iron bound to transferrin is there in circulation at any given time?
4mg
In what forms is iron stored?
Storage proteins (ferritin, homosiderin)
Where are the iron storage sites?
- Liver
- Bone marrow
- Spleen
What are the functions of iron?
- Hemoglobin and myoglobin
- Cytochromes and other enzymes involved in e- transport
- Monooxygenases and dioxygenases
- Peroxidases
- Oxidoreductases
- Pro-oxidant
What individuals are more vulnerable to iron deficiency?
- Infants, young children, adolescents
- Menstruating females
- Pregnant women
What are the consequences of iron deficiency?
W/ or w/o anemia –> not able to carry oxygen properly in blood
What is hemochromatosis?
- Chronic iron overload
- Genetic disorder
- Body cannot accurately sense iron stores and down-regulate intestinal absorption
What are the common sources of zinc?
- Red meats, seafood, poultry, pork
- Dairy
- Whole grains
- Veggies
- Supplements
What is the RDA of zinc for men vs. women?
- Men = 11 mg
- Women = 8 mg
How is zinc digested?
Hydrolyzed from amino/nucleic acids in stomach and small intestine?
What are the mechanisms by which zinc is absorbed?
- Carrier mediated active transport
- Passive diffusion and paracellular absorption w/ high intake
How is zinc transported?
Bound loosely to albumin in the blood
What transports zinc into the cell? (facilitates absorption)
ZIP4
What can zinc be bound to?
- Albumin
- Alpha-2 macroglobulin
- Immunoglobulin G
- Transferrin
What enhances zinc absorption?
- Ligands (citric acid, AAs)
- Acidic environment
What substances inhibit zinc absorption?
- Phytate
- Oxylate
- Polyphenols
- Folate
- Fe
- Ca
Where is zinc stored?
All organs, especially the liver, kidneys, skin, bones
In what forms is zinc stored?
Zn containing metalloproteins and liver metalloproteins
What are the functions of zinc?
- Interacts w/ proteins, enzymes, AAs, and peptides
- Regulation of transcription
- Bone formation
- Cell replication
- Skin integrity
- Immune health
- Carb metabolism
What are zinc fingers? What gives it this name? Location? Function?
- Proteins w/ a secondary structure or shape like a finger due, in part, to the presence of a Zn atom linked through cysteinyl or histidyl residues in the protein
- Found w/in many transcription factors, which bind to metal response/regulatory elements in the promoter regions of genes to enhance/inhibit transcription
What conditions increase the risk of Zn deficiency?
- Elderly
- Children of low income
- Vegetarians
- Alcoholics
- Trauma
- Sickle cell anemia
- Malabsorption
What are the common sources of copper?
- Organ meats
- Shellfish
- Nuts, seeds, legumes, dried fruits
What is the RDA for copper?
900 micrograms
How is copper digested?
- Bound to organic components in food
- Released in stomach, small intestine gastric HCl and pepsin
- Proteolytic enzymes in small intestine hydrolyze proteins further
How is copper absorbed? Where? Mechanisms?
- Small amount in stomach (low pH)
- Small intestine (active carrier-mediated transport, passive diffusion)
What substances enhance copper absorption?
- AAs
- Organic acids
What substances inhibit copper absorption?
- Phytate
- Zn
- Fe
- Excessive antacid ingestion (high pH)
How is copper transported in the blood? (what is it bound to?)
Bound loosely to albumin or transcuprein or AAs
How is copper transported in the liver? (what is it bound to?)
Bound to ceruloplasmin for transport
Where is copper stored?
- Liver
- Brain
- Kidneys
- Skeleton
What organ controls copper homeostasis?
Liver
What is copper bound to for storage?
- AAs
- Proteins
- Metallothionein
What are the functions of copper?
- Ceruloplasmin (iron oxidation and antioxidant)
- Superoxide dismutase (antioxidant)
- Cytochrome c oxidase (ATP production)
What are the consequences of copper deficiency?
- Kidney issues (nephrosis)
- GI malabsorption
- Impairment of certain antioxidant and energy production enzymes
What is the consequence of copper toxicity?
Wilson’s disease (genetic disorder)
What are the classifications of minerals? Amounts?
- Major minerals: > 100 mg/day
- Trace minerals:
How does the body respond to low calcium levels in the blood?
PTH will be released from the parathyroid gland and help break down bone for its calcium
Phosphorus is a component of what substances/molecules?
LOOK AT QUIZ
What is hemoglobin? What does it bind? Transport?
A protein in RBCs that can bind iron, and is used to transport oxygen
Absorption of heme vs. non-heme iron.
- Heme iron is absorbed into enterocytes through HCP1
- Non-heme iron is absorbed through DMT1
How does vitamin D interact w/ diff minerals?
Enhances absorption of Ca, P, Mg
List the main inhibitors of minerals.
- Phytates
- Oxalates
- Polyphenols
Which of the minerals do we need the most?
Calcium (1000 mg/day)
List the minerals in order of highest to lowest RDA.
- Calcium = 1000 mg/day
- Phosphorus = 700 mg/day
- Magnesium = 310-420 mg/day
- Iron = 8-18 mg/day
- zinc = 8-11 mg/day
- Copper = 900 micrograms/day
What is the main transporter of minerals?
Albumin
