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