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CPR Exam 2 > 5: RBC Biochem > Flashcards

5: RBC Biochem Flashcards

1
Q

Lifespan of an RBC

A

120 days

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2
Q

During what stage of erythropoiesis is the majority of Hb synthesized?

A

Before nulceus is extruded to form a reticulocyte from a normoblast

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3
Q

HbF composition

A

A 2 y 2

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4
Q

Two types of adult Hb composition

A

HbA: a 2 B 2
HbA2: a 2 D 2 (only 3%)

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5
Q

Iron positioning in heme before vs after O2 binds

A

Before: Fe slightly outside plane of porphyrin
After: moves into plane -> pulling down proximal histidine -> changes interactions with associated globin chains

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6
Q

Type of oxygen dissociation curve for hemoglobin vs myoglobin

A

Hemoglobin: sigmoid also (due to cooperativity)
Myoglobin: hyperbolic

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7
Q

Cooperative binding of Hb

A

Binding one molecule of O2 facilitates binding of another by pulling the proximal histidine downward

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8
Q

Partial pressure of O2 in the lungs

A

About 100 mmHg

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9
Q

Why is Fe an ideal catalyst for redox reactions

A

It readily exchanges electrons

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10
Q

Two states of iron

A

Ferrous: Fe2+
Ferric: Fe3+

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11
Q

Two major functions of Fe

A
  1. Oxygen transport via Hb

2. Component of cytochromes in ETC

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12
Q

Main way iron is regulated

A

Modulating absorption

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13
Q

Two major places iron is found in the body

A
  1. Hb: 67%

2. Stored iron as ferritin: 27%

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14
Q

What product is formed during ferritin breakdown

A

Hemosiderin

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15
Q

Main source of heme vs non-Heme iron

A

Heme: animal products on-heme: plant products

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16
Q

What does ferric reductase require to function?

A

Vitamin C

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17
Q

What does ferroportin require vs what regulates it?

A

Requires hephaestin, blocked by hepcidin

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18
Q

What happens when hepcidin binds ferroportin?

A

Internalization of ferroportin + degradation in lysosomes

19
Q

Three things that control levels of hepcidin

A
  1. Transferrin
  2. Transferrin receptor
  3. HFE: human homeostatic iron regulator protein
20
Q

Hepcidin expression when iron is high vs low

A

High iron: high hepcidin

Low iron: low hepcidin

21
Q

Causes of iron deficiency

A
  1. Insufficient dietary iron or absorption
  2. Excess blood loss
  3. Overuse of aspirin
  4. Ulcers of GI tract
22
Q

What type of anemia occurs from iron deficiency

A

Hypochromic microcytic anemia

23
Q

Two compounds necessary for RBC production

A

Folate, vitamin B12

24
Q

Why does a deficiency in vitamin B12 or folate cause anemia?

A

Diminished DNA synthesis

25
Where is folic acid found in diet?
Most foods - fruits, liver, eggs, milk, legumes, yeast, and especially leafy veggies
26
How much folate is stored in the liver?
5-10 mg, which can last 3-6 months
27
Methotrexate
Inhibits FH2 reductase -> antineoplastic agent
28
85% of B12 deficiency is due to what?
Lack of intrinsic factor
29
Test to determine cause of pernicious anemia
Schilling test
30
Describe part one of schilling test
1. Given Cobalt-labeled B12 + unlabeled B12 -> saturates receptors in liver so that if absorbed, will pass into urine 2. Urine collected for 24 hours 3. If radioactivity is present -> normal 4. If radioactivity NOT present -> pernicious anemia -> move to part 2
31
Describe part 2 of the schilling test
1. Give dose of cobalt-labeled B12 + intrinsic factor + some unlabeled B12 to saturate the receptors 2. Urine collected for 24 hours 3. If radioactive B12 present -> pernicious anemia due to lack of intrinsic factor
32
How many globular units comprise hemoglobin
Four
33
Describe a Porphyrin ring
Four 5-membered rings containing N connected by single carbon bridges
34
Two locations of heme biosynthesis
Liver, erythroid cells of bone marrow
35
What occurs with defects in heme synthesis?
Porphyrias
36
Major antagonist of ALA synthase
Heme
37
Two enzymes inactivated by Lead, especially in lead poisoning
1. ALA dehydratase | 2. Ferrochelatase
38
Lead poisoning - what accumulates and what is causes
ALA accumulates -> is neuro toxic -> neuro sx and anemia and energy metabolism is impacted
39
Porphyria
Genetic disorder caused by defects in heme synthesis
40
Acute hepatic vs erythropoietin porphyrias in general
Acute hepatic: neuro sx | Erythropoietin: skin sx, photosensitivity
41
What does porphyria mean in Greek?
Purple pigment
42
Which type of bilirubin is insoluble?
Unconjugated/indirect
43
What is added to bilirubin to make it conjugated?
Glucuronic acid
44
How does phototherapy work for jaundice?
Blue fluorescent light causes BR to undergo conversion into a more soluble isomer

CPR Exam 2 (22 decks)

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