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🥗Intro to Nutrition

Mineral Functions

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Why This Matters

Minerals are the unsung heroes of your body's daily operations—they don't provide calories, but without them, you couldn't build bone, carry oxygen, fire a nerve impulse, or even keep your heart beating in rhythm. In Introduction to Nutrition, you're being tested on more than just matching minerals to functions; you need to understand how minerals work at the cellular level, why deficiencies cause specific symptoms, and which minerals interact with each other in absorption and function.

The key to mastering this topic is recognizing that minerals fall into functional categories: some build structures, some carry molecules, some regulate fluid and electrical signals, and some protect cells or activate enzymes. Don't just memorize that calcium builds bones—know that it also enables muscle contraction and nerve signaling, which explains why severe deficiency causes muscle cramps and numbness. Think in mechanisms, not just lists.


Structural Minerals: Building Bones and Teeth

These minerals form the physical framework of your skeleton and teeth. Hydroxyapatite crystals—made primarily of calcium and phosphorus—give bones their rigid strength, while other minerals support the matrix that holds everything together.

Calcium

  • Primary component of hydroxyapatite—makes up about 99% of body calcium stored in bones and teeth
  • Enables muscle contraction by triggering the release of calcium ions from the sarcoplasmic reticulum, allowing actin-myosin binding
  • Essential for nerve impulse transmission and blood clotting; deficiency causes hypocalcemia with muscle spasms and tingling

Phosphorus

  • Second most abundant mineral in the body—combines with calcium in an approximate 1:2 ratio to form bone mineral
  • Critical component of ATP (adenosine triphosphate\text{adenosine triphosphate}), the body's primary energy currency
  • Maintains acid-base balance through phosphate buffer systems; also forms the backbone of DNA and RNA

Magnesium

  • Cofactor for over 300 enzymes—involved in protein synthesis, muscle function, and blood glucose control
  • Supports bone health by influencing calcium metabolism and contributing to bone crystal formation (about 60% stored in bone)
  • Required for ATP activation—ATP must bind to magnesium to be biologically active, making it essential for energy metabolism

Compare: Calcium vs. Phosphorus—both are major bone-building minerals stored primarily in the skeleton, but calcium also drives muscle contraction while phosphorus powers energy metabolism through ATP. If an exam question asks about mineral interactions, remember these two work as partners in bone formation.


Oxygen Transport and Cellular Energy

These minerals enable your cells to receive oxygen and produce energy. Without adequate iron and copper, oxygen delivery fails and energy production stalls—explaining why deficiency causes profound fatigue.

Iron

  • Central atom in hemoglobin's heme group—each hemoglobin molecule contains four iron atoms that reversibly bind oxygen for transport
  • Also found in myoglobin (muscle oxygen storage) and cytochromes (electron transport chain), making it essential for aerobic energy production
  • Most common nutritional deficiency worldwide—causes microcytic hypochromic anemia with symptoms of fatigue, pallor, and impaired cognitive function

Copper

  • Required for iron metabolism—ceruloplasmin (a copper-containing enzyme) oxidizes iron so it can bind to transferrin for transport
  • Essential for collagen cross-linking—copper-dependent lysyl oxidase strengthens connective tissue in blood vessels, bone, and skin
  • Supports antioxidant defense as part of superoxide dismutase (SOD); deficiency mimics iron deficiency because iron can't be properly utilized

Compare: Iron vs. Copper—both are essential for preventing anemia, but iron is the oxygen carrier while copper enables iron absorption and transport. This explains why copper deficiency can cause iron-deficiency-like symptoms even when iron intake is adequate.


Electrolytes: Fluid Balance and Nerve Function

Electrolytes are minerals that carry electrical charges when dissolved in body fluids. They create the electrochemical gradients that drive nerve impulses, muscle contractions, and fluid movement across cell membranes.

Sodium

  • Primary extracellular cation—regulates fluid volume outside cells and maintains blood pressure through the renin-angiotensin system
  • Essential for nerve impulse generation—sodium influx through voltage-gated channels creates action potentials
  • Works with glucose transporters for nutrient absorption in the intestines; excess intake linked to hypertension in salt-sensitive individuals

Potassium

  • Primary intracellular cation—maintains cell membrane potential and counterbalances sodium's effects on blood pressure
  • Critical for heart rhythm—abnormal potassium levels (hypo- or hyperkalemia) can cause life-threatening cardiac arrhythmias
  • Supports muscle contraction by repolarizing cell membranes after sodium depolarization; deficiency causes muscle weakness and cramps

Compare: Sodium vs. Potassium—both are essential electrolytes for nerve and muscle function, but they work on opposite sides of the cell membrane. Sodium is concentrated outside cells; potassium inside. The Na+/K+\text{Na}^+/\text{K}^+-ATPase pump maintains this gradient, which is why both minerals must be balanced for proper cardiovascular and neuromuscular function.


Thyroid Function and Metabolism Regulation

The thyroid gland requires specific minerals to produce hormones that control your metabolic rate. Iodine forms the structural core of thyroid hormones, while selenium activates them—making both essential for metabolism regulation.

Iodine

  • Structural component of thyroid hormonesT3\text{T}_3 (triiodothyronine) contains three iodine atoms; T4\text{T}_4 (thyroxine) contains four
  • Deficiency causes goiter (enlarged thyroid) and hypothyroidism; severe deficiency during pregnancy causes cretinism (irreversible intellectual disability)
  • Iodized salt programs have largely eliminated deficiency in developed countries, but it remains a global public health concern

Selenium

  • Required for thyroid hormone activation—selenoenzymes (deiodinases) convert T4\text{T}_4 to the more active T3\text{T}_3
  • Powerful antioxidant function as part of glutathione peroxidase, protecting cells from oxidative damage
  • Supports immune function—deficiency impairs both innate and adaptive immunity and increases susceptibility to viral infections

Compare: Iodine vs. Selenium—both are essential for thyroid function, but iodine builds the hormone structure while selenium activates it. A deficiency in either can impair metabolism, but iodine deficiency causes goiter while selenium deficiency may worsen existing thyroid conditions.


Immune Function and Tissue Repair

These minerals support your body's defense systems and ability to heal. They act as cofactors for enzymes involved in immune cell function, protein synthesis, and wound repair.

Zinc

  • Essential for immune cell development—required for T-cell maturation and function; deficiency increases infection susceptibility
  • Cofactor for over 100 enzymes including those involved in DNA synthesis, protein metabolism, and cell division
  • Critical for wound healing—supports collagen synthesis, cell proliferation, and inflammatory response; deficiency delays healing and causes skin lesions

Compare: Zinc vs. Copper—both support immune function and connective tissue health, but zinc is more directly involved in immune cell activity and wound healing, while copper focuses on iron metabolism and collagen cross-linking. Both are trace minerals with similar food sources (meat, shellfish), so deficiencies often occur together.


Quick Reference Table

ConceptBest Examples
Bone and tooth formationCalcium, Phosphorus, Magnesium
Oxygen transportIron, Copper
Energy metabolism (ATP)Phosphorus, Magnesium, Iron
Electrolyte/fluid balanceSodium, Potassium
Nerve impulse transmissionSodium, Potassium, Calcium
Thyroid hormone functionIodine, Selenium
Antioxidant protectionSelenium, Copper, Zinc
Immune functionZinc, Selenium

Self-Check Questions

  1. Which two minerals work together in bone formation, and what is the approximate ratio in which they're stored in hydroxyapatite crystals?

  2. Explain why copper deficiency can cause symptoms similar to iron deficiency anemia, even when dietary iron intake is adequate.

  3. Compare and contrast the roles of sodium and potassium in maintaining the electrochemical gradient across cell membranes. Why is balance between these two minerals critical for heart function?

  4. A patient presents with goiter and fatigue. Which two minerals should be evaluated, and what are their distinct roles in thyroid hormone metabolism?

  5. If an FRQ asks you to identify minerals involved in enzyme activation, which three would provide the strongest examples, and what types of reactions does each support?