Hematolology week 4 (rbc energy metabolism)

RBC energy metabolism Major Pathway:

Emden-Meyerhof Pathway

RBC energy metabolism Shunt:

• Hexose monophosphate or Pentose phosphate Pathway

• Methemoglobin Reductase Pathway

• Rapaport- Luebering Pathway

Emden-Meyerhof Pathway

Major energy provider

90% anaerobic glycolysis

glycolysis of Emden-Meyerhof Pathway

Glucose

______ enters the RBC without energy expenditure via the transmembrane protein GLUT - 1

Most common enzyme deficiency

Pyruvate Kinase

EMP

Converts glucose to lactic acid and generate a net ATP gain of 2 ATP molecules

Phases of Emden-Meyerhof Pathway

F1, 6-BP —> G3P —> 3-PG —> Pyruvate (2 ATP)

Emden-Meyerhof Pathway

- converts glucose to lactic acid

- generate a net ATP gain of 2 ATP molecules

Pyruvate kinase

most common enzyme deficiency

Hexose monophosphate or Pentose phosphate Pathway

detoxifies peroxide (H2O2), which arises from O2 reduction in the cell's aqueous environment, where it oOxygen xidizes and destroys heme iron, proteins, and lipids, especially lipids containing thiol groups.

10% AEROBIC GLYCOLYSIS

glycolysis of Hexose monophosphate

Detoxifying peroxide

HMP extends the functional life span of the RBC by

Hexose monophosphate or Pentose phosphate Pathway

- Reduction of NADP to NADPH

- Provides reduced glutathione

Reduction of NADP to NADPH

subsequently required to reduce glutathione

Reduced glutathione (GSH)

prevent oxidative denaturation of hemoglobin which makes it a protective mechanism

Glucose 6 phosphate dehydrogenase (G6PD)

provides the only means of generating NADPH for glutathione reduction, and in its absence, erythrocytes are particularly vulnerable to oxidative damage

Glucose 6 phosphate dehydrogenase (G6PD)

most common inherited enzyme deficiency and is associated with heinz bodies

Methemoglobin Reductase Pathway

converts methemoglobin back to normal hemoglobin using the methemoglobin reductase enzyme which makes it a corrective mechanism

Heinz Bodies

Bite Cells

Heme iron

constantly exposed to oxygen and peroxides.

Peroxide

oxidizes heme iron from the Ferrous (2+) to the Ferric (3+) state.

Methemoglobin

When the iron state is ferric, the affected hemoglobin molecule is called

Cytochrome b5 reductase / methemoglobin reductase

involved for reducing ferric iron into ferrous state

Rapaport- Luebering Pathway

- Generates 2,3 Diphosphoglycerate (2,3-DPG)

- important in the oxygen-carrying capability of erythrocytes.

Ferrous Iron

Reduced

Fe2

Found in RBCs

Ferric

Oxidized

Fe3

Bound to transferrin

Chocolate brown

2,3-diphosphoglycerate (2,3-DPG)

decreases hemoglobin affinity to oxygen

↑2,3DPG

↓Hb affinity to Oxygen

Shift to right

↓2,3DPG = ↑ Hb affinity to Oxygen

Shift to the Left

Oxygen Dissociation curve - Shift to the right

pH

PCO2

2,3-DPG

Temperature

Hb affinity for O2

“FACE RIGHT CADET”

pH - Decrease

PCO2 - Increase

2,3-DPG - Increase

Temperature - Increase

Hb affinity for O2 - Decrease

red blood cell ages

a decrease in its enzyme, a decrease in ATP, a decrease in size, and an increase in density

1%

mononuclear phagocytic system

___% of the red blood cells leave the circulation each day and broken down by the ____________________