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Biochemistry I/II > Lecture 28: Iron Metabolism > Flashcards

Lecture 28: Iron Metabolism Flashcards

1
Q

What type of mineral is iron?

A

Micromineral

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2
Q

Compare and contrast heme-bound iron vs. non-heme bound iron?

A

Heme-bound Iron: Found in animal tissues, greater absorption

Non Heme-Bound Iron: Found in plants, less absorption

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3
Q

Main function of iron?

A

O2 transport

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4
Q

While iron ____ is tightly regulated, there is no regulation of iron ____

A

Absorption; excretion

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5
Q

In what four tissues is iron distributed in?

A

1) Muscle (myoglobin)
2) Bone marrow (RBC)
3) Erythrocytes (hemoglobin)
4) Liver*
5) Intestine
6) Reticuloendothelial macrophages (destroy RBC)

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6
Q

What organ stores iron? What oran is important for iron absorption?

A

Storage: The liver
Absorption: Intestinal cells (enterocytes)

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7
Q
A
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8
Q

Iron is utilized in the bone marrow for ____ and in RBC’s for ____

A

Bone marrow: RBC production
RBC’s: O2 transport

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9
Q

What three structures are involved in absorption of non-heme iron?

A

1) Duodenal Cytochrome B: converts non-heme iron to Fe3+ to Fe2+ (Vit C required!)
2) DMT1: Transport iron into intestinal cell (enterocyte)
3) Ferritin(Fe3+): stores iron

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10
Q

What three structures are involved in absorption of heme-containing iron?

A

1) Heme Carrier Protein: allows iron to be transported into enterocyte (intestine cells)
2) Heme Oxygenase: breaks iron out of heme group, resulting in free iron
3) Ferritin: stores iron

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11
Q

What structure is the main intracellular structure for storing iron?

A

Ferritin

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12
Q

True or False:
Since ferratin has ferroxidase activity, it can convert Fe3+ to Fe2+

A

True

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13
Q

What three structures are important for iron export?

A

-Ferroportin
-Hephaestin
-Transferrin

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14
Q

What is the function of Hephaestin—a structure that is important for iron export?

A

Hephaestin: oxidizes Fe2+ to Fe3+

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15
Q

What is the function of Transferrin—a structure that is important for iron export?

A

Transferring binds and transports Fe3+ in the serum

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16
Q

Iron export takes places from what 3 structures?

A

1) Enterocytes
2) Hepatocytes
3) RE macrophages

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17
Q

How does iron import occur?

A

1) Transferrin bound to Fe3+ bind to the transferrin receptor (endocytosis)
2) Endosome will increase pH
3) Iron liberated from transferrin
4) Free iron leaves endosome via DMT1
5) Ferritin (storage)

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18
Q

What are the two main proteins that control iron transport?

A

1) Hepcidin: Negative regulator of iron transport
2) Erythroferrone: Positive regulator of iron transport

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19
Q

How does Hepcidin act as a negative regulator of iron transport?

A

When present, it binds to ferroportin and triggers its internalization. If ferroportin gets internalized, iron cannot be exported.

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20
Q

How does Erythroferrone act as a postive regulator of iron transport?

A

Represses the expression of hepcidin

21
Q

If someone has an infection, positive acute phase reactants such as ____ increase, leading to ____ ____. Taken together, this is known as _____

A

hepcidin
iron witholding
nutritional immunity

22
Q

True or False:
Reducing iron availability can slow down an infection

A

True

23
Q

How are hepcidin and serum iron levels affected during nutrional immunity?

A

Hepcidin: increases
Serum iron: decreases
Bacterial Growth: decreases

24
Q

Under low iron conditions, iron regulatory proteins (IRP’s) bind to ____, which result in the production of the ____ receptor

A

3’ iron responsive elements (IRE); transferrin receptor (allow for greater transport of iron)

25
Q

What happens to the iron regulatory protein (IRP) and the iron-responsive-element under high level iron conditions?

A

IRP do not bind to IRE. Therefore, there is less translation of transferrin receptor.

26
Q

The ___ ___ ___ is the RNA sequence found in the non-coding part of the transferrin mRNA

A

Iron Response Element

27
Q

___ is a condition caused by low hemoglobin. Symptoms include: extreme fatigue and dizziness.

A

Anemia

28
Q

______ is the type of anemia that is characteristic of an iron deficiency. In this disorder, circulating RBCs are smaller than the usual size of RBCs and have decreased red color

A

Microcytic hypochromic anemia

29
Q

What would you expect to see on CBC if one has anemia? (Hb, hematocrit?)

A

Low hemoglobin/hematocrit
Also: microcytic hypochromic anemia

30
Q

What populations may develop anemia?

A

1) Vegetarians
2) Pregnant women
3) Blood loss
4) Poor absorption conditions

31
Q

What vitamins can prevent anemia?

A

-Iron
-Vit C
-Folate
-B12

32
Q

You can develop anemia of chronic disease under what conditions?
If you have untreated chronic ____or ____; increased expression of ____, nutritional immunity, or iron witholding

A

inflammation; infection; hepcidin

33
Q

Anemia of chronic disease look similar to what type of anemia?

A

Microcytic hypochromic anemia

34
Q

Macrocytic Normochromiac Anemia is a result of deficiency in vitamin ____or ___

A

B12 ; folate

35
Q

True or False: Hereditary hemochromatosis is a condition in which minimal amounts of iron are made

A

False - excessive amounts of iron are made

36
Q

What is the cause of hereditary hemochromatosis? Treatment?

A

Mutations in hepcidin, ferroportin, and regulators of hepcidin

Treatment: phlebotomy

37
Q

Iron overload can occur by taking supplements. How can iron poisoning be treated?

A

Chelating agents

38
Q

What are the three positive acute phase reactants?

A

1) Ferritin
2) C Reactive Protein
3) Hepcidin

(Serum levels of these will elevate upon infection or inflammation)

39
Q

____ is the only iron (Fe2+) exporter

A

Ferroportin

40
Q

Where does iron import take place from?

A

1) Erythroid cells
2) Hepatocytes

41
Q

What three structures are important for iron import?

A

1) Transferrin: Binds and transports Fe3+
2) Transferrin Receptor: Binds Tf-Fe3+ and internalizes it
3) Divalent Metal Transporter: Exports Fe3+ out of endosome

41
Q

What three structures are important for iron import?

A

1) Transferrin: Binds and transports Fe3+
2) Transferrin Receptor: Binds Tf-Fe3+ and internalizes it
3) Divalent Metal Transporter: Exports Fe3+ out of endosome

42
Q

What are the three negative acute phase reactants?

A

1) Albumin
2) Pre-albumin

43
Q

What are the three negative acute phase reactants?

A

1) Albumin
2) Pre-albumin
3) Tranferrin

serum levels of these analytes decrease upon infection/inflammation

44
Q

________ are proteins that bind to the transferrin receptor mRNA and stabilize it to promote its translation/iron transport. They are inactivated by high iron levels.

A

Iron regulatory proteins

45
Q

What four structures are important for iron import?

A

1) Transferrin
2) Transferrin Receptor
3) Divalent metal transporter
4) Ferritin

46
Q

What does a CBC evaluate?

A

Hemoglobin
Hematocrit
RBC/WBC
Platlets

47
Q

What three markers could you use to assess iron status? Which would you prefer to use if person is feeling ill/has other infection/inflammatory conditions?

A

Ferritin, Transferrin, or Transferrin Receptor

48
Q

What value will elevate as anemia worsens?

A

Total iron binding capacity

Biochemistry I/II (23 decks)

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