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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
Q

Where is folic acid found in diet?

A

Most foods - fruits, liver, eggs, milk, legumes, yeast, and especially leafy veggies

26
Q

How much folate is stored in the liver?

A

5-10 mg, which can last 3-6 months

27
Q

Methotrexate

A

Inhibits FH2 reductase -> antineoplastic agent

28
Q

85% of B12 deficiency is due to what?

A

Lack of intrinsic factor

29
Q

Test to determine cause of pernicious anemia

A

Schilling test

30
Q

Describe part one of schilling test

A
  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
Q

Describe part 2 of the schilling test

A
  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
Q

How many globular units comprise hemoglobin

A

Four

33
Q

Describe a Porphyrin ring

A

Four 5-membered rings containing N connected by single carbon bridges

34
Q

Two locations of heme biosynthesis

A

Liver, erythroid cells of bone marrow

35
Q

What occurs with defects in heme synthesis?

A

Porphyrias

36
Q

Major antagonist of ALA synthase

A

Heme

37
Q

Two enzymes inactivated by Lead, especially in lead poisoning

A
  1. ALA dehydratase

2. Ferrochelatase

38
Q

Lead poisoning - what accumulates and what is causes

A

ALA accumulates -> is neuro toxic -> neuro sx and anemia and energy metabolism is impacted

39
Q

Porphyria

A

Genetic disorder caused by defects in heme synthesis

40
Q

Acute hepatic vs erythropoietin porphyrias in general

A

Acute hepatic: neuro sx

Erythropoietin: skin sx, photosensitivity

41
Q

What does porphyria mean in Greek?

A

Purple pigment

42
Q

Which type of bilirubin is insoluble?

A

Unconjugated/indirect

43
Q

What is added to bilirubin to make it conjugated?

A

Glucuronic acid

44
Q

How does phototherapy work for jaundice?

A

Blue fluorescent light causes BR to undergo conversion into a more soluble isomer

CPR Exam 2 (22 decks)

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