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Final Exam > Chap 6 > Flashcards

Chap 6 Flashcards

Erythrocyte Metabolism and Destruction

1
Q

3 layers of RBC Membrane?

A

Outermost: Glycolipids & Glycoproteins
Central: Cholesterol & Phospholipids
Inner: Cytoskeleton

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2
Q

Spectrin

A

Skeletal protein composed of Alpha and Beta globin chains.

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3
Q

Ankyrin

A

Binding site for Spectrin

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4
Q

Spectrin and Ankyrin are the components of which layer of the RBC membrane?

A

Cytoskeleton layer, inner most layer

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5
Q

RBC Membrane Function?

A

Shape of cell and provides permeability to water and electrolytes to exchange via cation pumps.

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6
Q

How do RBCs control volume and water content?

A

Primarily through control of Sodium and potassium content.

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7
Q

What are the RBC functions that require energy?

A
  1. Maintain Cation gradient
  2. Maintain phospholipid membrane and deformability
  3. Maintain functional Hb
  4. Initiate and maintain Glycolysis
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8
Q

What are the 4 key metabolic pathways for the Erythrocyte?

A

Glycolysis (Embden-Meyerhoff) (EMP)
Hexose Monophosphate Shunt
Methemoglobin Reductase
Rapoport-Luebering Shunt

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9
Q

Glycolysis (EMP) generates how much of the needed energy for RBCs?

A

90-95%

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10
Q

In the EMP pathway, glucose is metabolized to produce how many ATP?

A

2 molecules

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11
Q

What is the enzyme involved in the EMP?

A

Phosphofructokinase
Pyruvate Kinase (PK)

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12
Q

What are the functions of the EMP?

A

Maintenance of the RBCs:
Shape
Flexibility
Cation Pumps

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13
Q

Hexose Monophosphate Shunt (HMS) metabolizes how much glucose?

A

5-10%

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14
Q

HMS occurs aerobically or anaerobically?

A

Aerobically

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15
Q

What is the end product of the HMS?

A

NADPH

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16
Q

What is the enzyme involved W/ HMS?

A

Glutathione Reductase
G6PD

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17
Q

What is the function of HMS?

A

Protects the RBC from oxidative injury by detoxing accumulated peroxide.

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18
Q

What is the most common defect of the HMS?

A

Deficiency of G6PD

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19
Q

If the HMS is deficient, what happens to the globin?

A

Globin is denatured and then precipitates, referred to as Heinz bodies (HBs).

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20
Q

Methemoglobin Reductase Pathway (MHBR) maintains what?

A

Iron in the ferrous state (Fe 2+)

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21
Q

What is methemoglobin the result of?

A

Oxidation of heme iron, from the ferrous state to the ferric state (Fe 3+).

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22
Q

In the absence or deficiency of methemoglobin reductase, what accumulates?

A

Methemoglobin

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23
Q

What can methemoglobin not do, that other Hgbs can?

A

Carry oxygen.

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24
Q

What enzyme is involved W/ MHBR?

A

Methemoglobin Reductase

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25
Q

Functions of the MHBR?

A

Protects Hb from oxidation via NADPH.

26
Q

NADPH W/ methemoglobin reductase is more efficient at reducing what?

A

Methemoglobin

27
Q

The Rapoport-Leubering Shunt (RLS) helps the RBC do what?

A

Regulate oxygen transport during hypoxic or acid-base imbalance conditions.

28
Q

The RLS permits the accumulation of what, that is essential for maintaining normal oxygen tension and regulating hemoglobin oxygen affinity?

A

2,3-DPG (BPG)

29
Q

The accumulation of 2,3 DPG regulates?

A

Oxygen delivery to tissues

30
Q

What is the enzyme involved W/ RLB?

A

DPG Synthetase

31
Q

What are the 3 areas of RBC metabolism that are important for normal survival and metabolism?

A

RBC Membrane
Hemoglobin Structure and Function
RBC metabolic pathways (Cellular Energy)

32
Q

Which Erythrocyte metabolic pathway is responsible for providing the majority of Cellular energy?

33
Q

Which metabolic pathway regulates oxygen affinity?

34
Q

Which metabolic pathway maintains hemoglobin in a reduced state?

35
Q

Which metabolic pathway prevents oxidation of Hemoglobin by peroxide?

36
Q

Towards the end of its 120 day life cycle, RBCs begin to breakdown how?

A

Membrane is less flexible.
Concentration of cellular Hgb increases.
Enzyme activity diminished.

37
Q

Senescent RBCs

A

aging RBCs

38
Q

What removes senescent RBCs from circulation?

A

Reticuloendothelial System (RES)

39
Q

Reticuloendothelial System (RES)

A

a system of fixed macrophages, that are essential to removing senescent RBCs.

40
Q

Erythrocyte destruction occurs in 2 pathways?

A

Extravascular
Intravascular

41
Q

What is the % of extravascular RBC destruction?

42
Q

What is the % of intravascular RBC destruction?

43
Q

Steps of Extravascular RBC destruction?

A
  1. Hostile surrounding in spleen, stress RBC.
  2. Glycolysis slows, ATP production ends.
  3. Intracellular Na+ increases K+ decreases.
  4. Water enters cell, RBCs loose flexibility.
  5. RBCs are now trapped in Spleen.
44
Q

RES cells lyse RBC and digest them, what happens to the other RBC components?

45
Q

Iron after Extravascular RBC destruction?

A

Transported to BM via transferrin and used in Hgb or stored in macrophages (Nurse Cells).

46
Q

Amino acids after Extravascular RBC destruction?

A

Recycled into new globin chains.

47
Q

Protoporphyrin Ring of extravascular RBC destruction?

A

Broken down and converted to Biliverdin.

48
Q

The biliverdin from the protoporphyrin ring breakdown is converted to what?

A

Unconjugated Bilirubin

49
Q

What carries the newly unconjugated bilirubin to the liver?

A

The plasma protein Albumin

50
Q

Bilirubin is conjugated in the liver, before being excreted into?

A

The Intestine

51
Q

Intestinal flora convert the conjugated bilirubin into?

A

Urobilinogen

52
Q

How is most urobilinogen excreted?

53
Q

(T or F): The blood can pick up some of the Urobilinogen and it can be excreted in Urine as well?

54
Q

What can Conjugated (Direct) and Unconjugated (Indirect) bilirubin be used to monitor?

55
Q

What protein carrier picks up and binds W/ free Hgb A and B dimers?

A

Haptoglobin

56
Q

Haptoglobin

A

plasma protein that irreversibly binds free Hgb, forming a complex, that is broken down by Splenic Macrophages.

57
Q

When the Haptoglobin-Hemoglobin complex happens, where is it carried to?

A

The liver.

58
Q

Once in the Liver, the hapto-hgb complex, is broken down extravascularly by what cells?

59
Q

When increased intravascular destruction occurs, what may be all used up?

A

Haptoglobin

60
Q

When the haptoglobin is used up and free Hgb is excreted in the urine, it is called?

A

Hemoglobinuria

Final Exam (27 decks)

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