Trace Minerals

Question 1

Heme Iron

Answer 1

• found in meats and muscle tissue
• associated with red blood cells in muscle and blood from animal products
• bound to heme and absorbed into intestinal cells by a heme receptor

Question 2

Non-heme Iron

Answer 2

• less bioavailable
• found in leafy vegetables
• must be converted to Fe2+ from Fe3+ before it can be absorbed (vitamin C or other acids help with this)
• duodenal cytochrome B also helps convert non-heme iron to Fe2+

Question 3

What factors increase iron absorption?

Answer 3

vitamin C (non-heme only), gastric acid (non-heme), meat/fish/poultry (heme), and in pregnancy growth and menstration

Question 4

What factors decrease iron absorption?

Answer 4

phytates, oxalates, tannins, decreased need, calcium, antacids, zinc, and some preservatives

Question 5

How is heme iron absorbed across the intestine and transported in the body?

Answer 5

• Heme is taken up and transported across the cell by heme carrier protein (hcp1)
• Heme oxygenase removes iron from the hemoglobin ring
• It’s transported to ferritin for storage

Question 6

How is Ferrous iron absorbed across the intestine and transported in the body?

Answer 6

• Ferrous iron leaves the enterocyte through a ferroportin or iron regulatory protein 1 (IREG1)
• must be converted to Fe3+ before transporting

Question 7

How is Non-heme iron absorbed across the intestine and transported in the body?

Answer 7

• Non-heme iron must be reduced to ferrous state (by vitamin C or gastric acidity)
• Then transferred across the Divalent metal transporter (DMT1)
• Then delivered to ferritin for storage or it’s transported and delivered to the luminal side of the enterocyte

Question 8

How does iron regulate expression of transferrin and ferritin when iron stores are low ?

Answer 8

• uses iron response proteins (IRPs) to bind to the 5 prime end of ferritin and this blocks translation of the protein
• same IRPs bind to the 3 prime end of transferrin and this has the opposite effect
• it stabilizes the DNA so that more transferrin is made to transport iron to cells

Question 9

How does iron regulate expression of trasnferrin and ferritin when iron stores are high?

Answer 9

• IRPs leave the 5 prime end of ferritin so translation of this protein can continue
• When IRPs leave the 3 prime end of transferrin, the DNA become unstable and is destroyed

Question 10

Function of iron

Answer 10

Cofactor in hemoglobin synthesis and in other enzymes

Question 11

Iron-deficiency anemia

Answer 11

can’t synthesize hemoglobin without iron

• can make DNA because you have B12 and folate
• blood cells will be small, because you don’t have enough heme

Question 12

B12 or folate deficiency

Answer 12

can make heme, but can’t synthesize DNA to make new red blood cells
- blood cells will be big and fat with too much heme

Question 13

Function of zinc

Answer 13

Cofactor for the most enzymes of any minor mineral
- enzymes that affect pH regulation, ethanol metabolism, bone mineralization, antioxidation, immunity, and nucleic acid metabolism

Transcription factor to form zinc finger proteins

Question 14

Zinc Finger

Answer 14

• transcription factors made when zinc binds to cysteine and histidine residue in DNA
• can then bind to mRNA to control which sections of the gene are expressed

Question 15

How is zinc absorbed across the intestine and transported in the body?

Answer 15

• DMT1 transporter (active mechanism which requires ATP)

- Can be transported by the ZIP 4 transporter

Question 16

Why must zinc have a constant supply in your diet?

Answer 16

• There isn’t a good long term storage mechanism for it