27: Red Cell Metabolism - Schmidt

Question 1

erythrocytes lose nuclei __ entering circulation

Answer 1

before

mRNA disappears 1-2 d after release; no prtn synthesis, no replacement of damage, etc.

Question 2

old, inelastic RBC are trapped in ___ and phagocytosed by _____

Answer 2

spleen; macrophages

extravascular hemolysis - no RBC lysis in vasculature

Question 3

hereditary spherocytosis –>

Answer 3

spectrin mutation leads to rounded, short-lived cells

defects of cytoskeleton shorten RBC lifespan

Question 4

neonatal jaundice, failed phototherapy, blood analysis shows hemolysis –> what might it be?

Answer 4

G6PD deficiency

infant has a problem producing NADPH leading to hemolysis

Question 5

intravascular v. extravascular hemolysis

Answer 5

intravascular: mechanical disruption, relase of hemoglobin from RBC –> hemoglobinuria
extravascular: normal, removal of stiff RBC, relase of bilirubin from RBC, possible jaundice

Question 6

4 purposes of RBC metabolism

Answer 6

• keeping iron reduced in Fe2+ form (NADH)
• maintaining K/Ca gradients (ATP)
• keeping prtn SH groups reduced (NADPH)
• maintaining cell shape (ATP)

Question 7

If RBC metabolism fails (3 things) …

Answer 7

• cells fill with Ca2+
• cells release K+
• lose biconcave shape

Question 8

Red blood cell eats…

Answer 8

only glucose as an energy source

insulin has no effect on RBCs

Question 9

look at slide 11

Answer 9

energy clutch and electron sources

Question 10

what is the purpose of the energy clutch?

Answer 10

keep degrading 1.2bisphosphoglycerate even if no ADP available

Question 11

2 regulated steps of glycolysis in RBC

Answer 11

• hexokinase
• phosphofructokinase I

acidic pH inhibit glycolysis - less lactate producton

Question 12

acidic environment –> low 2,3 BP glycerate –>

Answer 12

increased binding affinity of oxygen to RBC

acidosis reduces 2,3BPG production

acidosis reduces 23BPG concentration and improves oxygen saturation

Question 13

hemolytic crises triggered by:

Answer 13

infection, H2O2 producing drugs, Fava beans

Question 14

see RBC with a bite taken out of them by a macrophage

Answer 14

G 6PD deficiency

also heinz body

Question 15

blebbing of outer membrane of the RBC

Answer 15

pyruvate kinase deficiency

Question 16

tumor cells get energy from..

Answer 16

glycolysis

produce large amounts of lactate

express hypoxia inducible factor 1a to support anaerobic metabolism

Question 17

what is the cytoskeleton of RBCs like

Answer 17

mesh of spectrin under the PM with glycophorin and/or band/4.2/ankyrin anchoring to the membrane

Question 18

most common cytoskeletal defect

Answer 18

hereditary spherocytosis

“rounding off of cells”

most commonly an ankyrin mutation but could be others

Question 19

is glycolysis in RBC insulin dependent?

Answer 19

nope

Question 20

provides reduction equivalents in the form of NADPH

Answer 20

PPP pentose phosphate pathway

Question 21

low intraceullar NADPH –>

Answer 21

activates G6PD

pentose products are re-introduced into glycolysis

Question 22

importance of glutathiione

Answer 22

GSH keeps sulfhydryl groups reduced

provides electrons to convert H2O2 to H20

Question 23

what converts O2- to H2O2

Answer 23

superoxide dismutase

Question 24

causes hemolytic anemia for lack of NADPH

Answer 24

G6PD deficiency

PPP defect

Question 25

causes hemolytic anemia for lack of NADH/ATP

Answer 25

pyruvate kinase deficiency

glycolysis defect