4) RBC metabolism

Question 1

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

Answer 1

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

Question 2

prinicipal, almost exclusive source of RBC energy

Answer 2

glucose

Question 3

4 RBC metabolic pathways

Answer 3

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

Question 4

90% of glucose metabolism occurs via the…

produces what?

Answer 4

EM pathway

pyruvate or lactate, ATP, and NADH

Question 5

ATP needed in RBC for…

Answer 5

• maintaining shape and deformability
• operate Na/K pumps

Question 6

NADH is needed in RBC for…

Answer 6

reduction of methemoglobin to hemoglobin

Question 7

no net energy produced from glycolysis

Answer 7

if LR pathway is used

Question 8

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

Answer 8

2,3-diphosphoglycerate

Question 9

10% of RBC glucose is metabolized through the…

Answer 9

HMS/PPP

Question 10

2 ways of reducing methemoglobin

Answer 10

• nonenzymatically via glutathione
• enzymatically via methemoglobin reductase

Question 11

sequence of events when RBC is exposed to oxidant drugs

Answer 11

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

Question 12

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

Answer 12

Heinz bodies (aggregates of oxidated globin chains)

hemolytic anemia

Question 13

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

Answer 13

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

Question 14

cause accumulation of H2O2

Answer 14

oxidant drugs
infection

Question 15

Hexose monophosphate shunt

H2O2 oxidizes ——- to ——- via ——-

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

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

Answer 15

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

Question 16

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

Answer 16

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

Question 17

Methemoglobin reductase pathway

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

Answer 17

NADH and methemoglobin give NAD and hemoglobin, via methemoglobin reductase

Question 18

——% mHgb gives hypoxia and cyanosis

Answer 18

20-40%

Question 19

LR pathway gives accumulation of ———-

Answer 19

2,3-DPG

Question 20

O2 + Hgb =

Answer 20

oxyhemoglobin

Question 21

OH released from deoxyhemoglobin…

Answer 21

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

5% of CO2 carried in solution

Question 22

3 ways of transporting CO2

Answer 22

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%)

Question 23

chloride shift

Answer 23

HCO3 moves out of RBC, Cl moves in

Question 24

factors that affect affinity of O2 and Hgb

Answer 24

• pO2
• pCO2
• temperature
• pH
• 2,3-DPG

Question 25

shift from deoxyhgb to oxyhgb when...

Answer 25

3rd heme is oxygenated

Question 26

responsible for sigmoid shape

Answer 26

heme-heme interaction

Question 27

tense state relaxed state

Answer 27

2,3-DPG present, deoxygenated 2,3-DPG expelled, increased O2 affinity

Question 28

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

Answer 28

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

Question 29

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

Answer 29

pH and pO2

Question 30

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

Answer 30

beta

Question 31

------- and O2 are competitive

Answer 31

2,3-DPG

Question 32

p50 value

Answer 32

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

Question 33

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

Answer 33

less

Question 34

3 abnormal hemoglobin pigments

Answer 34

- carboxyhemoglobin (HbCO) - methemoglobin (Hi) - sulfhemoglobin (SHb)

Question 35

HbCO results in...

Answer 35

death from anoxia cherry red blood

Question 36

toxic level of CO

Answer 36

5.0g%

Question 37

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

Answer 37

218

Question 38

2 types of methemoglobinemia

Answer 38

- hereditary - acquired (most common; drug effects)

Question 39

2 types of hereditary methemoglobinemia and tx

Answer 39

- **MR enzyme deficiency**—tx with ascorbic acid, methylene blue - **HgbM**, abnormal structure with enhanced tendency toward oxidation—no response to reducing agents

Question 40

SHb

Answer 40

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

Question 41

causes of SHb

Answer 41

sulfur-containing drugs TNT explosives

Question 42

SHb (does/does not) respond to reducing agents

Answer 42

does not

Question 43

toxic SHb level

Answer 43

0.5 g%

Question 44

Answer 44

heinz bodies