Erythrocyte Biochemistry Flashcards Preview

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Flashcards in Erythrocyte Biochemistry Deck (26):
1

Structure of hemoglobin

Tetramer of four helical peptide chains (2 alpha and 2 beta globin chains in adults) with a heme group containing reduced iron (Fe2+) in the center

2

T State of hemoglobin

occurs in the absence of oxygen

3

R state of hemoglobin

occurs when oxygen binds

4

Cooperativity of hemoglobin is exhibited by

When one oxygen binds a heme group within hemoglobin, it induces a conformation change in the ring (by pulling the iron into the plane of the ring) which induces a conformational change in other rings that make it bind oxygen more easily

5

Effects of 2,3-BPG, H+, and CO2 on the oxygen dissociation curve of hemoglobin

All shift the curve to the right
2,3-BPG reduces the affinity of hemoglobin for oxygen
H+ -- Bohr effect

6

HBF

fetal hemoglobin
does not bind well to 2,3-BPG, therefore it has a higher affinity for oxygen than maternal hemoglobin - probably important

7

Iron is absorbed by enterocytes in the _____ State

Fe2+ state

8

Ferritin

stores Fe3+ in enterocytes

9

Ferroportin

Transports Fe2+ out of enterocyte into lumen
activated by low dietary iron
inhibited by hepcidin and high dietary iron

10

Hemochromatosis

caused by unregulated duodenal reabsorption of iron due to low levels of hepcidin
or (?)
deficient ferroportin results in an overabundance of iron - cirrhosis, arthritis, endocrinopathy, skin pigmentation, cardiomyopathy

treat with bloodletting

11

Hepcidin

regulates iron content in the body
binds ferroportin when iron is high and causes it to be internalized and destroyed by proteolysis

when iron levels are low, hepcidin isnt expressed and doesnt tag ferroportin

regulated by Hfe (TF that binds trf2 to express hepcidin)

12

Transferrin

transports Fe3+ to liver, spleen and bone marrow
activated by low stored iron
inhibited by high stored iron

13

Iron deficiency consequences

fatigue and anemia
deficiency results from insufficient diet
depletion can occur from bleeding

14

Iron overload consequences

Iron poisoning -->
1)Hemochromatosis
2)Hemosiderosis
3)Sideroblastic anemia

15

Hemosiderosis

ferritin is degraded into insoluble hemosiderin which accumulates (in alcoholics and blood transfusion recipients)

alvealoar hemorrhage can result

16

Sideroblastic anemia

impaired heme synthesis --> iron buildup in mitochondria
pale skin, fatigue, enlarged spleen

17

B12 and B9 necessary for the production of

Red blood cells
deficiency of either can cause megaloblastic anemia due to diminished DNA synthesis

18

N5-methyl THF (dietary folate) requires _____ to be _____ to become folic acid

cobalamin
demethylated

19

Cobalamin is composed of

nucleotide, protoporphyrin like ring, cobalt, sugar, nitrogen ring

20

Cobalamin is absorbed by

binding R binder proteins made by mucosa in stomach
pancreatic enzymes degrade R protein in the duodenum

Parietal cells also in the stomach release intrinsic factor, which picks up B12 in the duodenum and carries it to the ileum, where it is absorbed by cubulin

21

R-binder proteins

produced by mucosa cells in the stomach
bind cobalamin in the stomach and carry it to the duodenum before it is degraded by pancreatic enzymes

22

Intrinsic factor

produced by parietal cells in the stomach
binds cobalamin in the duodenum and carries it to the ileum where it is absorbed by cubilin

23

Cubilin

receptor in the ileum that absorbs intrinsic factor bound cobalamin

24

Transcobalamin

carries cobalamin in the blood

25

Megaloblastic macrocytic anemia

Large erythrocytes - normal hemoglobin content in relation to size
can result from B6/B12 deficiency (co factors in DNA synthesis required for production of so many RBCs in a day)
Bone marrow will exhibit large erythroblasts and hypersegmented neutrophils

26

Pernicious Anemia

Vitamin B12 deficiency as a result of lack of intrinsic factor (necessary for uptake in the duodenum) as a result of lack of gastric mucosa due to autoimmune diease or decreased protein production