1
Q
Vitamins
A
- Organic compounds (minerals are inorganic)
- Not synthesized in adequate amounts by the body
- Not used for energy (not catabolized to CO₂ + H₂O)
- Often function as coenzymes
- Two classes: water-soluble and fat-soluble
2
Q
Essential Elements
A
- 6 essential organic elements → building blocks of nearly all organic molecules
- ~16 essential inorganic elements → specialized physiological roles
3
Q
Classification by Requirement
A
Macro elements (>100 mg/day): calcium, phosphorus, magnesium, sodium, potassium, chloride Micro/trace elements (1–100 mg/day): iron, zinc, manganese, copper, fluorine Ultra-trace (<1 mg/day): selenium, iodine, chromium → Low requirement ≠ low importance
4
Q
Physiological Roles of Essential Elements
A
- Intracellular signaling and trafficking
- Enzyme catalysis
- Molecular structure and synthesis
- Antioxidant defense
- Hormone function
5
Q
Anemia
A
- ~⅓ of world population affected
- ~50% due to iron deficiency
- Defined as low hemoglobin, not low iron
6
Q
Hemochromatosis
A
- Genetic disorder
- Iron overload with excess tissue deposition
7
Q
Hepcidin
A
- Liver-derived hormone
- Inhibits ferroportin → ↓ iron release and absorption
- ↑ with inflammation and iron loading
- ↓ with iron deficiency and erythropoiesis
8
Q
Oxidation States
A
- Ferrous iron (Fe²⁺): soluble, absorbable
- Ferric iron (Fe³⁺): insoluble, transport/storage form
9
Q
Why Iron Is Essential
A
- Oxygen transport (hemoglobin, myoglobin)
- Brain development
- Cellular metabolism
- Enzyme systems and electron transfer
10
Q
Heme Iron
A
- Absorbed intact → high bioavailability
- Found in hemoglobin, myoglobin
- Present in cytochrome P450, peroxidases
11
Q
Non-Heme Iron
A
- Found in Fe-S clusters and single-iron enzymes
- Requires reduction and transport
before absorption
12
Q
Key Protein Examples
A
- Hemoglobin: carries 4 O₂ per molecule
- Cytochrome P450: detoxification enzymes * Ribonucleotide reductase: oxygen-bridged iron for DNA synthesis
13
Q
Adult Iron Distribution
A
- Functional iron: ~78% (Hb, myoglobin, enzymes)
- Storage iron: ~22% (ferritin, hemosiderin) * Transport iron: ~0.001% (transferrin)
- ~⅔ of total iron is in hemoglobin
14
Q
Iron Losses & Needs
A
- Basal loss: males ~1.0 mg/day,
females ~0.75 mg/day - Menstruation: up to ~1.5 mg/day
- Highest needs: growth, pregnancy, blood loss
15
Q
Infants
A
- 0–6 months: AI (no EAR)
- Rapid growth
- Iron supplied as lactoferrin (highly bioavailable)
16
Q
DRIs
A
- Higher: females, pregnancy, lactation, vegetarians (×1.8)
- Lower: oral contraceptive users
- Lowest: males
17
Q
Heme Iron (Animal-Only)
A
- Red meat, fish, poultry
- 45–65% of animal iron is heme
18
Q
Non-Heme Iron (Animal + Plant)
A
- Legumes, grains, vegetables, fortified foods (LGVF)
19
Q
Food Source Quality
A
Excellent: clams, beef liver, parsley Moderate: tuna, tofu, beef, cereals, tomato, broccoli
Lower: eggs, chicken, dairy, oatmeal, fruit
20
Q
Heme Iron
A
- Released during digestion
- Absorbed intact via HCP-1
- Minimal regulation
21
Q
Non-Heme Iron
A
- Released as Fe³⁺
- Reduced to Fe²⁺ by DCYTB
- Transported by DMT1
- Highly regulated and inhibitor-sensitive
22
Q
Enterocyte Transport Sequence
A
Iron released from food Fe³⁺ reduced to Fe²⁺ Fe²⁺ enters via DMT1 —>Iron binds —> cytosolic proteins Export via ferroportin Oxidation to Fe³⁺ by hephaestin Binding to transferrin in plasma
23
Q
Enterocyte Turnover
A
- Lifespan ~3 days
- Retained iron lost when cells slough
24
Q
Enhancers
A
- Vitamin C
- Acidic pH
- Meat factor protein
- Organic acids (citric, lactic)
- Mucin
25
Inhibitors
* Phytates, polyphenols, fiber
* Oxalates, tannins
* Calcium, zinc, manganese, nickel
* Alkaline pH
26
Absorption Example (15 mg Intake)
* ~7.5 mg solubilized
* ~4 mg enters mucosa
* ~1.5–2.0 mg enters plasma
27
Transferrin
* Plasma iron transport protein
* Binds Fe³⁺
* Carries 2 iron atoms
* ~30% saturated normally
28
Ferritin
* Cytosolic storage of Fe³⁺
* Safe, soluble, regulated
* Low = depletion, high = overload
29
Hemosiderin
* Lysosomal storage
* Seen in iron overload
30
Ferritin Structure
* 24 subunits (H + L)
* H-rich: detox tissues (brain, heart)
* L-rich: storage tissues (liver, spleen)
31
Hepcidin Decreases With
* Iron deficiency
* Erythropoietic demand
* Hypoxia
32
Hepcidin Increases With
* Inflammation
* High iron
* BMP signaling (HJV)
33
Effect
* Binds ferroportin → degradation
* ↓ iron export and absorption
34
Erythropoiesis
* Occurs in bone marrow
* Stimulated by erythropoietin (kidney, hypoxia)
* Requires ~24 mg iron/day
* Also requires B12 and folate
* Heme synthesized in mitochondria
35
Recycling & Turnover
* Dietary absorption: 1–2 mg/day
* Iron recycled from RBCs: ~2300 mg
* Ferritin + hemosiderin: ~500 mg
* Myoglobin: ~400 mg
36
Transferrin Saturation
* <30%: deficient
* <15%: erythropoiesis impaired
* >60%: overload
37
Ferritin
* Normal: – Males 18–270 ng/mL – Females 18–160 ng/mL
* <18: depletion
* High: overload/inflammation
38
Hemoglobin
* Normal: females 120–160 g/L, males 135–175 g/L
* Anemia: <110 females, <125 males
39
Iron Deficiency Progression
Storage depletion: ↓ ferritin Functional deficiency: ↓ transferrin saturation Iron-deficiency anemia: ↓ Hb, ↓ MCV
40
Diagnostic Patterns
Iron deficiency anemia: ↓ hepcidin, ↓ ferritin, ↑ sTfR
Anemia of inflammation: ↑ hepcidin, normal-high ferritin
Mixed: intermediate pattern
NUTR 302 Topic 1 -Iron
flashcards
Decks in class (7)
# Cards
