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Mercy CLS 6: Hematology > 2) RBC structure > Flashcards

2) RBC structure Flashcards

1
Q

3 main parts of RBC essential for survival and function

A
  • membrane
  • hemoglobin
  • metabolic pathways
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2
Q

3 layers of RBC membrane and components

A
  1. outer layer —glycolipids, glycoproteins, proteins
  2. central layer —proteins, cholesterol, phospholipids
  3. inner layer —proteins
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3
Q

chemical composition of RBC membrane

A

40% lipids
52% proteins
8% carbs

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4
Q

used to separate RBC membane proteins

A

SDS polyacrilamide gel electrophoresis (SDS-PAGE)

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5
Q

examples of integral proteins

A
  • glycophorins A, B, C
  • Band 3
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6
Q

most important integral protein

A

glycophorin A

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7
Q

2 functions of band 3

A
  • anion exchange channel
  • anchors cytoskeleton to the lipid bilayer
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8
Q

functions of glycophorins (3)

A
  • accounts for membrane sialic acid, giving RBCs a negative charge (repels others)
  • location of many antigens
  • anchors cytoskeleton to bilayer
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9
Q

examples of peripheral proteins

A
  • spectrin
  • ankyrin
  • adducin
  • band 4.1
  • band 4.2
  • actin
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10
Q

most abundant peripheral protein

A

spectrin

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11
Q

structure of spectrin

A

helix of two polypeptide chains (α,β)
They form dimers which link with other αβ chains to form tetramers.
The chains bind with other peripheral proteins to form a skeletal network that creates the “cytoskeleton”.

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12
Q

acts like a strong spring, giving membrane deformability

A

spectrin

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13
Q

functions of the cytoskeleton

A
  • strengthens membrane
  • protects cell from shear forces
  • controls shape and deformability
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14
Q

tie network of cytoskeleton together

A

the 2 spectrin complexes

require energy to stay together

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15
Q

critical to RBC survival as it passes through vessels, and for O2 delivery

A

deformability

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16
Q

2 causes of ↓ deformability

A
  • loss of ATP; ↓ phosphorylation of spectrin
  • deposits of Ca2+; ↑ membrane rigidity
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17
Q

extravascular sequestration

A

spleen function
cells are squeezed through small sinusoidal orifices, and removed or fragmented

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18
Q

passively transported across RBC membrane

A
  • H2O
  • anions (Cl and HCO3)

travel through band 3

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19
Q

actively transported across RBC membrane

A

Na+ and K+

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20
Q

intracellular:extracellular ratios for Na and K

A

Na—1:12
K—25:1

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21
Q

Na-K pumps prevent ——- hemolysis

A

osmotic

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22
Q

3 RBC membrane lipids

A
  • phospholipids
  • glycolipids
  • cholesterol
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23
Q

Changes in body lipid transport and metabolism may cause abnormalities in —————– that may alter RBC membrane composition.

A

plasma phospholipid concentration

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24
Q

interact with many glycoproteins to form antigens

A

glycolipids

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25
Q

RBC cholesterol is in continual exchange with…

A

unesterified plasma cholesterol

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26
Q

RBC morphology abnormality

proportional ↑ phospholipid & ↑ cholesterol in membrane

A

target cells

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27
Q

RBC morphology abnormality

abetalipoproteinemia with cholesterol accumulation in membrane (↑chol:PL ratio)

A

acanthocytes

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28
Q

↓ LCAT (lecithin cholesterol acyltransferase)

A

schistocytes & target cells

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29
Q

RBC morphology abnormality

↓ phosphorylated or altered spectrin

A

bite cells & spherocytes

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30
Q

RBCs are —–% Hgb

A

34%

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31
Q

Hgb is produced in…

A

65% in nRBCs
35% in reticulocytes (last stage in which hgb is made)

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32
Q

structure of hgb

A
  • 4 heme groups (4 Fe + 4 protoporphyrin IX rings)
  • 4 globin chains
33
Q

carries Fe to young RBC

A

transferrin

34
Q

after Fe is added, it goes to the ———– for insertion in to the protoporphyrin ring

A

mitochondria

35
Q

major sites of heme synthesis

A
  • young RBCs of marrow
  • hepatocytes
36
Q

ALA term

A

aminolevulinic acid

37
Q

byproducts of heme synthesis that do not produce heme

A

uroporphyrinogen I
coproporphyrinogen I

38
Q

lab tests measure ——— rather than unstable ———

A

porphyrins
porphyrinogens

39
Q

only type —– isomers of porphyrins form heme

A

III

40
Q

vitamin required for heme synthesis

A

Vit B6

41
Q

In conditions with ineffective utilization of protoporphyrin, there are ↑ amounts of…

A

free erythrocyte protoporphyrins (FEPs)

42
Q

lead inhibits…

A

ALA dehydrase
ferrochelatase

43
Q

porphyria

A

defect in porphyrin synthesis, especially inherited

44
Q

most common secondary porphyria

A

lead poisoning

45
Q

ways to classify primary porphyrias

A
  • organ —hepatic vs erythropoietic
  • symptoms —neurological or cutaneous
46
Q

neurological porphyrias

A
  • acute intermittent porphyria
47
Q

mixed porphyrias

A
  • variegate porphyria
  • hereditary coproporphyria
48
Q

cutaneous porphyrias

A
  • porphyria cutanea tarda
  • congenital erythropoietic porphyria
  • erythropoietic protoporphyria
49
Q

neurological porphyria sx

A
  • acute attacks
  • ↑ ALA and PBG in urine
  • abd pain
  • weakness
  • nausea
  • constipation
  • perspiration
  • HTN
  • tachycardia
  • motor dysfunction
  • sensory loss
  • mental disturbances
50
Q

cutaneous porphyria sx

A
  • photosensitivity
  • characteristic skin lesions
  • no ALA/PBG (no neuro sx)
51
Q

congenital erythropoietic porphyria sx

A
  • ↑ uro I and copro I (feces, RBCs)
  • splenomegaly
  • brown pigment to teeth; fluoresces
  • blistering
  • pink urine
52
Q

enzyme defect of PBG deaminase

A

acute intermittent porphyria

53
Q

enzyme defect of protoporphyrin oxidase

A

variegate porphyria

54
Q

enzyme defect of coproporphyrinogen oxidase

A

hereditary coproporphyria

55
Q

enzyme defect of uroporphyrinogen decarboxylase

A

porphyria cutanea tarda

56
Q

enzyme defect of ferrochelatase

A

erythropoietic protoporphyria

57
Q

enzyme defect of uroporphyrinogen III cosynthase

A

congenital erythropoietic porphyria

58
Q

↑ ALA in urine
↑ PBG in urine

A

acute intermittent porphyria

59
Q

↑ ALA, PBG in urine
↑ proto in feces
↑ copro in feces

A

variegate porphyria

60
Q

↑ ALA, PBG during attacks
↑ copro in feces

A

hereditary coproporphyria

61
Q

↑ uro
↑ copro isomer I

A

porphyria cutanea tarda

62
Q

↑ proto in RBC and feces
↑ FEP

A

erythropoietic protoporphyria

63
Q

↑ uro I
↑ copro I

A

congenital erythropoietic porphyria

64
Q

king george

A

variegate porphyria

65
Q

most common porphyria

A

porphyria cutanea tarda

66
Q
  • —— and —— are water soluble so appear in urine.
  • —— may be found in urine or feces.
  • —— is found only in feces.
A

PBG and uro
copro
proto

67
Q

globin chain production takes place in…

A

ribosomes in cytoplasm of nRBCs and retics

68
Q

globin chains on chromosome 16 and 11

A

16: zeta, alpha
11: beta, gamma, delta, epsilon

69
Q

3 types of normal adult hgb, structure, prevalence

A
  • Hgb A—2𝛼, 2β—97%
  • Hgb A2—2𝛼, 2δ—3.5%
  • Hgb F—2𝛼, 2𝛾—<1%
70
Q

we differentiate types of hgb by…

A

hgb electrophoresis

71
Q

Fe in each heme is ———–; binding sites:

A

hexacovalent
4 —binding N of protoporphyrin
1 —binding histadine in globin
1 —reversibly binding O2

72
Q

Fe in hemoglobin
Fe in methemoglobin

A

ferrous (Fe2+)
ferric (Fe3+) — no value in respiration

73
Q

globins and protoporphyrins won’t accumulate without one another, but —– will, causing…

A

iron
organ damage
pappenheimers (ferritin aggregates)
siderocytes/sideroblasts
ringed sideroblasts

74
Q

how does hemoglobin production change through gestation and infancy?

A

<3 months: Gower and Portland hgb (𝛇 and 𝛆)
Hgb F replaces these
20th week—β production begins
Birth—mostly Hgb F, some Hgb A
6 months—<8% Hgb F
1 year—<2% Hgb F

75
Q
A

target cells

76
Q

rate limiting step for heme synthesis
influenced by EPO

A

1) glycine and succinyl CoA to δALA

77
Q
A

acanthocytes

78
Q
A

schistocytes

Mercy CLS 6: Hematology (25 decks)

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