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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
Functions of the MHBR?
Protects Hb from oxidation via NADPH.
26
NADPH W/ methemoglobin reductase is more efficient at reducing what?
Methemoglobin
27
The Rapoport-Leubering Shunt (RLS) helps the RBC do what?
Regulate oxygen transport during hypoxic or acid-base imbalance conditions.
28
The RLS permits the accumulation of what, that is essential for maintaining normal oxygen tension and regulating hemoglobin oxygen affinity?
2,3-DPG (BPG)
29
The accumulation of 2,3 DPG regulates?
Oxygen delivery to tissues
30
What is the enzyme involved W/ RLB?
DPG Synthetase
31
What are the 3 areas of RBC metabolism that are important for normal survival and metabolism?
RBC Membrane Hemoglobin Structure and Function RBC metabolic pathways (Cellular Energy)
32
Which Erythrocyte metabolic pathway is responsible for providing the majority of Cellular energy?
EMP
33
Which metabolic pathway regulates oxygen affinity?
RLB
34
Which metabolic pathway maintains hemoglobin in a reduced state?
MHBR
35
Which metabolic pathway prevents oxidation of Hemoglobin by peroxide?
HMS
36
Towards the end of its 120 day life cycle, RBCs begin to breakdown how?
Membrane is less flexible. Concentration of cellular Hgb increases. Enzyme activity diminished.
37
Senescent RBCs
aging RBCs
38
What removes senescent RBCs from circulation?
Reticuloendothelial System (RES)
39
Reticuloendothelial System (RES)
a system of fixed macrophages, that are essential to removing senescent RBCs.
40
Erythrocyte destruction occurs in 2 pathways?
Extravascular Intravascular
41
What is the % of extravascular RBC destruction?
90%
42
What is the % of intravascular RBC destruction?
10%
43
Steps of Extravascular RBC destruction?
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
RES cells lyse RBC and digest them, what happens to the other RBC components?
Recycled
45
Iron after Extravascular RBC destruction?
Transported to BM via transferrin and used in Hgb or stored in macrophages (Nurse Cells).
46
Amino acids after Extravascular RBC destruction?
Recycled into new globin chains.
47
Protoporphyrin Ring of extravascular RBC destruction?
Broken down and converted to Biliverdin.
48
The biliverdin from the protoporphyrin ring breakdown is converted to what?
Unconjugated Bilirubin
49
What carries the newly unconjugated bilirubin to the liver?
The plasma protein Albumin
50
Bilirubin is conjugated in the liver, before being excreted into?
The Intestine
51
Intestinal flora convert the conjugated bilirubin into?
Urobilinogen
52
How is most urobilinogen excreted?
Poop
53
(T or F): The blood can pick up some of the Urobilinogen and it can be excreted in Urine as well?
True
54
What can Conjugated (Direct) and Unconjugated (Indirect) bilirubin be used to monitor?
Hemolysis
55
What protein carrier picks up and binds W/ free Hgb A and B dimers?
Haptoglobin
56
Haptoglobin
plasma protein that irreversibly binds free Hgb, forming a complex, that is broken down by Splenic Macrophages.
57
When the Haptoglobin-Hemoglobin complex happens, where is it carried to?
The liver.
58
Once in the Liver, the hapto-hgb complex, is broken down extravascularly by what cells?
RES Cells
59
When increased intravascular destruction occurs, what may be all used up?
Haptoglobin
60
When the haptoglobin is used up and free Hgb is excreted in the urine, it is called?
Hemoglobinuria
61

Final Exam (27 decks)

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