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BIIC > Biochem > Flashcards

Biochem Flashcards

1
Q

What major proteins determine RBC flexibility?

A 
Spectrin
Actin
Band 4.1
Band 4.2
Ankyrin
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2
Q

Hereditary Spherocytosis

A

Deficiency or abnormality in spectrin and less frequently in ankyrin, band 3, 4.1, or 4.2.

Symptoms: Spherocytes have short lifespan, hemolytic anemia, splenomegaly

Genetic: affect 1 in 5000 of Northern European ancestry Autosomal Dominant*

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3
Q

Hereditary Elliptocytosis

A

RBC assume elliptic shape

Abnormalities affect spectrin or, less frequently band 4.1 or glycophorin C.

Lower oxygen transport

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4
Q

Explain the Metabolism used in RBC Generally.

A

Glycolysis: ATP synthesis, production of 2,3 BPG, Reduction of Fe3+ to Fe2+

Pentose phosphate pathway. Role of NADPH in RBC

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5
Q

Specifically describe Anaerobic Glycolysis of RBC

A

Each glucose gives:
2ATP
2NADH
2Pyruvate

NAD+ is regenerated through lactate producation. Lactate is sent to liver for Cori cycle to be made back into glucose.

2,3 BPG is produced in RBC from 1,3 bisphophoglycerate by a Mutase. Can be sent back to glycolysis by Rappoport Luebering shunt through a phosphatase**

2,3 BPG is an allosterically regulator of )2 binding to Hb
It is increased when adapting to high altitudes. It binds to the 4 hemoglobins to keep them together.

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6
Q

Specifically HMP Shunt in RBC metabolism.

What is the Rate-limiting step?

Oxidative vs Nonoxidative Reactions

A

Oxidative Reactions:
Has three irreversible steps

Rate-limiting step: Glucose 6-phosphate dehydrogenase

Nonoxidative Reactions:
Reversible steps interconverting sugars with 3 C to 7 C.
Use Transaldolase and Transketolase (uses thiamine in TPP via vit. B1).
—Transketolase is important in diagnosis of thiamine deficiency.

Oxidative and Nonoxidative pathways are interconnected. Can make Ribose 5-phosphate for nucleotide biosynthesis. (ONLY used in the precursors). Oxidative reactions are used to make NADPH

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7
Q

Explain Pyruvate Kinase Deficiency

A

Results in Hemolytic Anemia (nonspherocytic)

Symptoms: fatigue, pale skin, SOB, jaundice, increase risk of gall sones.

2nd most common after G6PD deficiency. Can be distinguished from G6PD deficiency by lack of Heinz bodies (precipitated hemoglobin)

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8
Q

What are the biological roles of NADPH

A

Electron donor in biosynthesis of:

  • FA
  • Cholesterol
  • Steroids

Electron donor for the neutralization of ROS:

  • Hydrogen peroxide
  • Superoxide O22-
  • Hydroxyl radical

Provides reducing equivalents for Cytochrome P450 mono oxygenate system:

  • Biosynthesis of steroids
  • Detoxification of xenobiotics

Plays role in phagocytosis- destruction by macrophages and neutrophils

Substrate for the synthesis of Nitric oxide (NO)

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9
Q

What are the sources of NADPH in RBC?

A

On the HMG shunt (pentose phosphate pathway)

It reduces 2 GSH (Glutathione) to change H2O2 to 2 H2O.

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10
Q

Explain G6PD Deficiency

A

Episodic Hemolytic anemia induced by oxidative stress

Caused by oxidant stress: Infections, Certain drugs, and Fava beans

RBC contain Heinz bodies (precipitated hemoglobin)

One of the most common single gene disorders

X-linked recessive (Males are mostly affected)

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11
Q

What are the Variants of G6PD Deficiency and its effects on Blood?

A

Class 1: Very Severe: Chronic nonspherocytic hemolytic anemia.

Class 2: Severe: Acute hemolytic anemia less than 10% (G6PD Mediterranean)

Class 3: Moderate 10-60% of enzyme left (G6PD A)

Class 4: No symptoms: More than 60% of enzyme left

Mutations result in stability problems mostly

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12
Q

What are the causes of G6PD Deficiency?

A

Infections
Drugs:
-Antimalarials (Dapsone, Primaquine, Methylene blue)
-Analgesics/Antipyretics (Phenazopyridine, high doses of Aspirin)
-Antibacterials (Cortimoxazole, sulfadiazine, Qunollones, Nitrofurantoin)

Fava Beans: Bind to decrease GSH levels in RBC by Divicine and isouramil.

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13
Q

What are the kinds of anemia, their functional deficit and possible causes

A

Microcytic- Impaired hemoglobin synthesis
- Iron deficiency, mutation leading to thalassemia, lead poison

Macrocytic: Imparied DNA synthesis
- Vitamin B12 or Folic acid deficiency

Normocytic: Red cell loss
-Acute bleeding, sickle cell, RBC metabolic defects

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14
Q

Explain the structure of Heme

What are the proteins that use Iron?

A

4 pyrrole rings joined via methenyl bridges with a metal iron ion.

Heme can form 6 bonds. 4 with pyrrole rings and 2 with oxygen.

Hemoglobin Fe2+
Myoglobin Fe2+ :O2 storage in muscle
Cytochrome: Fe2+-3+. :ETC
Cyt P450: Fe2+-3+. :Hydroxylation
Catalase: Fe2+-3+. :Degradation of H2O2
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15
Q

Where is Heme synthesized?

Where is it Degradated

A

85% in the bone marrow. Requires Iron.

Degraded in Mononuclear phagocyte system (MPS) in the spleen, liver, and bone marrow.

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16
Q

Explain the bonding a and B Hemes in hemoglobin

A

The B and a chains have strong interactions to make aB dimers.

The interactions between the dimers are weaker ionic and hydrogen bonds.

Those bonds between the dimers are even weaker in the “relaxed” oxygenated state of hemoglobin.

T “Taut” state without oxygen
R “relaxed” state with oxygen

17
Q

Explain changing P50 based on changes in affinity of hemoglobin for O2

A

Increase in P50 reflects a decrease in affinity (shift right)

Decrease in P50 reflects an increase in affinity (shift to the left)

18
Q

Explain the transport of iron from food to the body, and what regulates it?

A

Fe2+ is bound to hemoglobin and is available to be taken right into the blood stream. Found in animals

Fe3+ Ferric iron needs an enzyme to make it bioavailable.

Hepcidin is used to down regulate the export of Fe into the blood.

19
Q

Why is hemoglobin a better transporter of oxygen to tissues.

A

It’s P50 is located around 26 mmHg. This curve is also steepest at the PO2 in tissue. So slight changes of PO2 in tissues will allow for oxygen transport from Hb to the tissue. Myoglobin will hold tight to its oxygen.

20
Q

How does pH affect affinity of oxygen for hemoglobin?

A

A decrease in pH will shift the curve to the right decreasing the affinity of oxygen to hemoglobin.

At low pH a greater PO2 is required to achieve any given oxygen saturation.

21
Q

Explain the Bohr effect and CO2 Transport

A

Protonation of Hb stabilizes the deoxy form (Taut) and decreases in the oxygen affinity for O2. As CO2 binds to side chains, O2 is released in tissue.

In the longs, the Oxygen saturation promotes O2 binding and converts the Hb to the R (relaxed) form which releases the protons to bind with bicarbonate to make carbonic acid which is cleaved to release CO2 to be exhaled.

22
Q

What are the allosterically effectors that change the P50 curve?

A

P02
PCO2
PH changes
2,3 BPG

23
Q

What does 2,3 BPG do to O2 affinity in Hemoglobin

A

In the Taut form, 2,3 BPG binds to Hb and and that shifts the curve right to help unload oxygen.

It can’t bind to the relaxed form, and is ejected from the T form as O2 is bound.

Without 2,3 BPG is affinity of O2 would be too high to effectively release O2 to tissues.

24
Q

What determines the overall blood O2 concentration

Does it help with saturation of O2?

A

Hb content

It is independent of SaO2 (O2 saturation)

25
Q

How does CO affect O2 saturation?

What is the related disorder

A

CO bound to Hb increases the affinity of O2 to Hb and so it can not release the O2 to the tissues

You get CO poisoning (constant cherry red color that persists in death)

26
Q

What is HbA1C

A

It is glucosindated a2B2 hemoglobin.

It is an indicated of prediabetes and diabetes.

5.7-6.4 is pre, over 6.5 is diabetes.

Shows glucose over last 120 days.

27
Q

Explain O2 transport to Fetus

A

HbF only weakly binds 2,3 BPG and has a higher affinity for O2 compared to adult Hb.

This facilitates transfer from maternal circulation across the placenta to the RBC of the fetus.

28
Q

Explain HbC disease

A

Generally mild condition associated with mild chronic hemolytic anemia without infarctive crisis

Doesn’t need any specific therapy.

29
Q

On a cathode test where does each type of normal and disordered Hb move?

A

HbA normal towards positive

HbS sickle in middle

HbC Problem in B globin negative.

30
Q

Explain Sickle Cell Disease

What is the benefit?

A

A point mutation of Glutamate to Valine. Causes rigid sticky fibers.

Can cause occlusion of capillaries and microinfarcts in tissues.

Being heterozygous for sickle cell shortens the life of RBC and stops malaria.

31
Q

Explain B Thalassemia

A

Disorder of chromosome 11 for B-globin.

There is one on each gene. Disorder in one is minor, on both is major B thalassemia.

Excess a-globin chains that are normal can’t form stable tetramers and die prematurely. This causes anemia.

32
Q

A-Thalassemia?

What are the names of the different kinds.

A

2 copies for a-globin on each chromosome 16 for 4 copies.

With one mutation you are a silent carrier. With 2 mutations you get minor defects

3 mutations is HbH disease showing hemolytic anemia

4 mutation is Hb Bart which results in Fetal death.

33
Q

What are Methemoglobinemias?

A

They can be Congenital or Acquired?

Certain drugs or oxidative stress can oxidize iron in Hb to methemoglobin. Usually it is turned back to hemoglobin using NADH-cytochrome b5 reductase, but in the event that there is too much it can cause hypoxia, and dark colored methemoglobin.

Congenital disorders GI are defects to the NADH-cytochrome b5 reductase or you can produce HbM resistant to the reductase.

This can cause the Kentucky Blue People

BIIC (8 decks)

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