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Clinical Problem Solving > 4 - Sickle Cell Disease > Flashcards

4 - Sickle Cell Disease Flashcards

1
Q

Why is it difficult to bind the first oxygen to hemoglobin?

A

Hemoglobin is in its T form when oxygen is low

Remember: first drink on a night out

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2
Q

Until which age Is HbF present in the blood?

A

6 months

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3
Q

What are the 3 components of a hemoglobin molecule?

A
  1. 4 globin subunits
  2. 4 heme units
  3. 4 ferrous ions
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4
Q

Concentration of which 2 substances controls blood pH?

A
  1. H+ ions

2. CO2

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5
Q

Which 4 body parts are most commonly affected by sickle crises?

A
  1. Bone
  2. Chest
  3. Brain
  4. Kidney
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6
Q

How would you diagnose sickle cell disease in a newborn?

A

Heel prick test

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7
Q

Which component of the blood binds H+ ions?

A

Hemoglobin

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8
Q

Why is oxygen readily picked up in the lungs, but given up easily to the tissues?

A

Hemoglobin’s AFFINITY for oxygen varies dramatically over a small range of oxygen levels

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9
Q

Sickle cell disease makes the transition of hemoglobin from its T form to its R
form ___ likely.

A

Less

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10
Q

Which secondary protein structure looks like a loop?

A

Alpha helix

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11
Q

Which organ destroys most of the body’s defective red blood cells?

A

Spleen

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12
Q

Why is oxygen given to patients in a sickle cell crisis?

A

Increased oxygen encourages hemoglobin to adopt its R form, reducing polymerisation

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13
Q

Compare the partial pressure of oxygen in the lungs and the tissues.

A

Lungs: higher
Tissues: lower

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14
Q

What is the secondary structure of a protein?

A

Local spatial arrangement of polypeptide backbone

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15
Q

Which component of proteins determines their tertiary structure?

A

R groups

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16
Q

Compare the symptoms of sickle cell trait and sickle cell disease.

A

Trait: asymptomatic
Disease: symptomatic; hemolysis, vaso-occlusion

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17
Q

In sickle cell patients, anemia does not have a huge impact on their quality of life. List 2 reasons why.

A
  1. It’s easier for hemoglobin to GIVE UP oxygen to tissues in its T state
  2. Increased PUMPING of blood helps compensate for low amounts of hemoglobin
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18
Q

2 carriers for sickle cell disease have a child. What is the chance that the child will have the disease?

A

1 in 4

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19
Q

Describe the process by which sickle cell disease causes cells to deform.

A

Hemoglobin polymerizes in its T form ->
Repeated oxygenation/deoxygenation cycles causes repeated distortions ->
Cells eventually stiffen and remain distorted

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20
Q

What percentage of Africans are carriers for sickle cell disease?

A

25%

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21
Q

Why might patients with sickle cell disease experience pain?

A

Vaso-occlusion of capillaries by stiff RBCs blocks blood flow, causing ischemia and infarction of downstream tissue

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22
Q

List 2 consequences of high bilirubin production.

A
  1. Jaundice

2. Gallstones

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23
Q

Why do RBC have a shortened life in sickle cell disease?

A

Repeated cycles of hemoglobin distortion weakens RBC

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24
Q

Describe the process by which a sickle crisis arises.

A

RBC must distort to fit through the capillaries ->
Sickled cells do not distort ->
Block the capillaries ->
Infarction of downstream tissues

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25
The HbS mutation is found on which protein subunits?
Beta
26
The sickling process in general terms results in 2 broad consequences. What are these?
1. Hemolysis (shorter RBC lifespan -> hemolytic) | 2. Vaso-occlusion (RBC stiffness -> blocking of capillaries)
27
Compare ischemia and infarction.
Ischemia: obstructed blood flow; tissue still alive Infarction: obstructed blood flow; tissue dead
28
What are the two forms of hemoglobin?
1. R | 2. T
29
How does a slightly reduced negative charge lead to a sickled shape in RBC?
Molecules in tense form polymerise
30
What is the result of imbalance between RBC production and loss in sickle cell disease?
Anemia
31
Which component of the blood is responsible for transporting oxygen?
Hemoglobin
32
Compare the genotype for sickle cell trait and sickle cell disease.
Trait: HbAS Disease: HbSS
33
What form of hemoglobin exists in low oxygen environments?
T
34
What form of hemoglobin exists in high oxygen environments?
R
35
Which form of hemoglobin binds oxygen? | R
Remember: RELAXED, loves to bind oxygen
36
Which amino acid mutation causes sickle cell disease?
Glutamic Acid -> Valine
37
What type of subunits are there in normal adult hemoglobin, and how many are there of each type?
2 alpha | 2 beta
38
Why has sickle cell trait persisted in some populations?
Carrier status helps protect against malaria
39
What is the inheritance pattern for sickle cell disease?
Autosomal recessive
40
List 2 advantages conferred by the biconcave shape of normal RBC.
1. More flexible | 2. Increased surface area for oxygen uptake
41
Which base pair mutation causes sickle cell disease?
Adenine -> Thymine
42
What is the quaternary structure of a protein?
Arrangement of multiple tertiary structures
43
Sickle cell disease gives hemoglobin a slightly reduced affinity for oxygen. How would this present on an oxygen dissociation curve?
Right shift
44
In sickle cell disease, a valine replaces a glutamic acid in the beta chain. How does this affect the charge of the molecule?
Slightly reduced negative charge
45
The core function of hemoglobin is the transport of O2 and ___.
CO2
46
List 4 factors that decrease hemoglobin’s affinity for oxygen (i.e., right shift).
1. Increased CO2 2. Increased H+ 3. Increased 2,3-DPG 4. Increased temperature Remember: Isabel Chang Has 2 Tits
47
What is splenomegaly?
Abnormal enlargement of the spleen
48
How does the subunit structure of the hemoglobin in a person with sickle cell disease differ from normal adult hemoglobin?
A beta subunit is replaced with a defective unit
49
Which form of hemoglobin gives up oxygen? | T
Remember: TENSE, does not want to bind oxygen
50
What is the average lifespan of an RBC?
120 days
51
List 4 factors that increase hemoglobin’s affinity for oxygen (i.e., left shift).
1. Decreased CO2 2. Decreased H+ 3. Decreased 2,3-DPG 4. Decreased temperature Remember: Drew Carey Has 2 Testicles
52
What is hematopoiesis?
The process by which blood cells are formed
53
Why does it get progressively easier to bind oxygen to hemoglobin?
Hemoglobin transitions to its R form as oxygen increases | Remember: additional drinks on a night out
54
What is the definitive diagnostic test for HbS?
Hb electrophoresis
55
The definitive diagnostic test for HbS is by Hb electrophoresis, which plots out different hemoglobins. However, in an urgent situation, there is a rapid bedside screening test (Sickledex) which uses a solubility method. What are the limitations of this test?
Cannot differentiate between sickle cell trait (HbAS) and sickle cell disease (HbSS)
56
What is the tertiary structure of a protein?
Its three-dimensional shape
57
Which component of proteins determines their secondary structure?
Amino acids
58
What are the 2 most common secondary protein structures?
1. Alpha helix | 2. Beta-pleated sheet
59
List 4 clinical sequalae of sickle cell disease.
1. Sickle crises 2. Infections 3. Splenomegaly 4. Jaundice
60
What is the secondary structure of collagen?
Triple helix
61
Where are RBC produced?
Bone marrow
62
List 5 triggers that increase cell sickling.
1. Low oxygen 2. Dehydration 3. Cold 4. Infection 5. Acid blood
63
What is the shape of the hemoglobin dissociation curve?
Sigmoid
64
Which secondary protein structure looks like a plane with many folds?
Beta-pleated sheet
65
List 4 treatments for a sickle crisis.
1. Oxygen 2. Antibiotics 3. Painkillers 4. Fluids
66
Which organ conjugates and excretes bilirubin?
Liver
67
What is the primary structure of a protein?
A linear sequence of amino acids
68
Which component of hemoglobin binds oxygen?
Heme
69
What is the only cure for sickle cell disease?
Bone marrow transplant
70
There are many different abnormal hemoglobins. What is the name given to the hemoglobinopathy suffered by people living around the Mediterranean basin?
Thalassemia
71
What causes jaundice?
Accumulation of bilirubin in the blood
72
What are 2 symptoms of infarction?
1. Pain | 2. Fever
73
Define infarction.
Tissue death caused by inadequate blood supply

Clinical Problem Solving (10 decks)

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