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Mercy CLS 6: Hematology > 4) RBC metabolism > Flashcards

4) RBC metabolism Flashcards

1
Q

4 things an RBC must do during its lifespan that require energy

A
  1. keep hgb in reduced form (Fe2+)
  2. operate Na-K pump to maintain volume
  3. keep membrane deformable
  4. produce NADPH
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2
Q

prinicipal, almost exclusive source of RBC energy

A

glucose

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3
Q

4 RBC metabolic pathways

A
  • Embden-Meyerhoff pathway (glycolysis)
  • Luebering-Rapaport pathway (2,3-DPG pathway)
  • Hexose monophosphate shunt (PPP)
  • Methemoglobin reductase pathway
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4
Q

90% of glucose metabolism occurs via the…

produces what?

A

EM pathway

pyruvate or lactate, ATP, and NADH

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5
Q

ATP needed in RBC for…

A
  • maintaining shape and deformability
  • operate Na/K pumps
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6
Q

NADH is needed in RBC for…

A

reduction of methemoglobin to hemoglobin

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7
Q

no net energy produced from glycolysis

A

if LR pathway is used

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8
Q

accounts fo 2/3 of RBC phosphorus
chief regulator of O2 transport and delivery

A

2,3-diphosphoglycerate

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9
Q

10% of RBC glucose is metabolized through the…

A

HMS/PPP

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10
Q

2 ways of reducing methemoglobin

A
  • nonenzymatically via glutathione
  • enzymatically via methemoglobin reductase
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11
Q

sequence of events when RBC is exposed to oxidant drugs

A
  • GSH is oxidized to GSSG
  • Fe3+ is oxidized to Fe2+
  • sulfhydryl groups of hgb are oxidized
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12
Q

if oxidative stress continues, ———– attach themselves to the cell membrane and are removed by spleen, which can cause…

A

Heinz bodies (aggregates of oxidated globin chains)

hemolytic anemia

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13
Q

2 ways oxidation can affect RBC, and the pathway that responds

A
  1. oxidation of Fe2+ to Fe3+ (methemoglobin)—MRP
  2. oxidation of globin chains (Heinz bodies)—HMS/PPP
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14
Q

cause accumulation of H2O2

A

oxidant drugs
infection

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15
Q

Hexose monophosphate shunt

H2O2 oxidizes ——- to ——- via ——-

——- is oxidized to ——-, giving GSH, via ——-

——- combines with ——- to form NADPH, via ——-

A

H2O2 oxidizes GSH to GSSG via glutathione peroxidase

NADPH is oxidized to NADP, giving GSH, via glutathione reductase

NADP combines with G6P to form NADPH, via G6PD

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16
Q

if the HMS is deficient, the amount of reduced ——– will be insufficient, and oxidants within the cell will…

A

glutathione
oxidize hgb sulfhydryl groups, leading to globin denaturation (Heinz bodies)

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17
Q

Methemoglobin reductase pathway

——- and methemoglobin give ——- and hemoglobin, via ——-

A

NADH and methemoglobin give NAD and hemoglobin, via methemoglobin reductase

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18
Q

——% mHgb gives hypoxia and cyanosis

A

20-40%

19
Q

LR pathway gives accumulation of ———-

A

2,3-DPG

20
Q

O2 + Hgb =

A

oxyhemoglobin

21
Q

OH released from deoxyhemoglobin…

A

combines with CO2 to form carbonic acid, which then dissociates to form bicarbonate

5% of CO2 carried in solution

22
Q

3 ways of transporting CO2

A
  1. in solution (5%)
  2. direct, carbamate molecule (20%)
  3. indirect, forming carbonic acid and then bicarb in RBC, after which chloride shift occurs (70%)
23
Q

chloride shift

A

HCO3 moves out of RBC, Cl moves in

24
Q

factors that affect affinity of O2 and Hgb

A
  • pO2
  • pCO2
  • temperature
  • pH
  • 2,3-DPG
25
Q

shift from deoxyhgb to oxyhgb when…

A

3rd heme is oxygenated

26
Q

responsible for sigmoid shape

A

heme-heme interaction

27
Q

tense state
relaxed state

A

2,3-DPG present, deoxygenated

2,3-DPG expelled, increased O2 affinity

28
Q

factors that decrease Hgb affinity for O2 (right shift), allowing O2 to be released into tissues

A

↑ temperature
↑ 2,3-DPG
↓ pH (Bohr effect)
↓ pO2
↑ pCO2

29
Q

concentration of intra-erythrocytic 2,3-DPG affected mostly by…

A

pH and pO2

30
Q

during deoxygenation, —— chains pull apart, allowing 2,3-DPG to bind

A

beta

31
Q

——- and O2 are competitive

A

2,3-DPG

32
Q

p50 value

A

pO2 at which Hgb is 50% saturated with O2, under standard temp/pH conditions

33
Q

O2-Hgb affinity will be (greater/less) in rapidly metabolizing tissues

A

less

34
Q

3 abnormal hemoglobin pigments

A
  • carboxyhemoglobin (HbCO)
  • methemoglobin (Hi)
  • sulfhemoglobin (SHb)
35
Q

HbCO results in…

A

death from anoxia
cherry red blood

36
Q

toxic level of CO

A

5.0g%

37
Q

affinity for CO is ——x greater than that for O2

A

218

38
Q

2 types of methemoglobinemia

A
  • hereditary
  • acquired (most common; drug effects)
39
Q

2 types of hereditary methemoglobinemia and tx

A
  • MR enzyme deficiency—tx with ascorbic acid, methylene blue
  • HgbM, abnormal structure with enhanced tendency toward oxidation—no response to reducing agents
40
Q

SHb

A

Hgb binds sulfur rather than O2
very stable compound, lasts until RBCs die
normal RBC lifespan

41
Q

causes of SHb

A

sulfur-containing drugs
TNT explosives

42
Q

SHb (does/does not) respond to reducing agents

A

does not

43
Q

toxic SHb level

A

0.5 g%

44
Q
A

heinz bodies

Mercy CLS 6: Hematology (25 decks)

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