Hemoglobinometry and Erythrocyte Features

Comprehensive vocabulary flashcards covering erythrocyte features, hemoglobin synthesis, derivatives, hemoglobinopathies, and clinical methods of hemoglobin determination (hemoglobinometry) based on the lecture transcript.

Cyanmethemoglobin method

The widely accepted clinical laboratory determination of hemoglobin that involves converting hemoglobin into hemoglobin cyanide.

Erythrocyte biconcavity

The flattened, biconcave disc shape of an RBC that ensures a large surface area to volume ratio for efficient gas exchange and results in a pinkish color when stained with Romanowsky stain.

MCV Reference Range

$80-100\,cu\,\mu$ ($\mu m^3$) or femtoliters ($fL$).

MCHC Reference Range

$32-36\%$.

MCT

Mean Corpuscular Thickness (or Mean Average Corpuscular Thickness), with a normal range of $1.7\,\mu - 2.5\,\mu$.

RBC Membrane composition

Approximately $8\%$ carbohydrates, $52\%$ proteins, and $40\%$ lipids.

Transmembrane proteins

Proteins in the RBC membrane that channel ions, water, and glucose, and provide vertical support to maintain cell shape.

Protoporphyrin IX

A ring of carbon, hydrogen, and nitrogen atoms that, together with a central atom of divalent ferrous iron, makes up heme.

Methemoglobin

An oxidized form of hemoglobin where iron is in the ferric state ($Fe^{3+}$), rendering it unable to bind with oxygen.

Hemoglobin Tetramer

The structure of hemoglobin consisting of four globin polypeptide chains ($2\alpha$ and $2\beta$), each with a heme molecule attached.

Heme Synthesis start

Begins in the mitochondria with the amino acid glycine and succinyl-CoA forming $\delta$-aminolevulinic acid (ALA).

Globin Gene Loci

$\alpha$ and $\zeta$ genes are on chromosome 16; $\epsilon$, $\gamma$, $\delta$, and $\beta$ genes are on chromosome 11.

Hb A1 (Hb A)

The major hemoglobin in adults ($90\%$) composed of $\alpha_2\beta_2$ chains.

Hb A2

A minor adult hemoglobin composed of $\alpha_2\delta_2$ chains, comprising less than $3.5\%$ or $5\%$ of total hemoglobin.

Hb F (Fetal Hemoglobin)

Hemoglobin composed of $\alpha_2\gamma_2$ chains; it is the primary form in fetuses and remains in small amounts ($<2\%$) in adults.

Erythropoietin (EPO)

A protein produced by the peritubular cells of the kidney that regulates RBC production in response to tissue hypoxia.

Reference Interval: Men

$14-18\,g/dL$ ($140-180\,g/L$).

Reference Interval: Women

$12-16\,g/dL$ ($120-160\,g/L$).

Deoxy-Hb color

Purple (associated with cyanosis when concentration is $>5\%$).

Carboxy-Hb color

Cherry red.

Sulfhemoglobin

A greenish, irreversible hemoglobin derivative formed by a sulfur atom addition to the pyrrole ring, often due to drugs like sulfonilamides.

Qualitative Hemoglobinopathy

A defect in the amino acid sequence, such as the Valine to Glutamic Acid substitution at the 6th position in Sickle-cell Anemia.

Quantitative Hemoglobinopathy

A partial or complete depression of the synthesis of one of the polypeptide chains, such as in Thalassemia.

Alkali Denaturation Test

A specific identification test used for Hb F (Fetal Hemoglobin).

Katayama's test

A test for carboxyhemoglobin using ammonium sulphate and acetic acid, yielding a rose red color for positive results.

Sickledex

A commercial test for Hb S based on the insolubility of sickling hemoglobin in certain buffers, resulting in turbidity.

Iron Content Method (Wong)

An accurate chemical method for hemoglobin determination based on the constant that $1.0\,gram$ of $Hb$ contains $3.47\,mg$ of $Fe$.

Gasometric Method

Measurement using the Van Slyke apparatus based on the principle that $1.0\,gram$ of $Hb$ can combine with $1.39\,ml$ of $O_2$.

Specific Gravity Method

A gravimetric method using copper sulfate ($CuSO_4$) solutions with specific gravities ranging between $1.048-1.066$.

Drabkin's Solution components

Contains Potassium ferricyanide ($K_3Fe(CN)_6$), Potassium cyanide ($KCN$), Sodium bicarbonate ($NaHCO_3$), and a surfactant.

540 nm

The wavelength at which the absorbance of cyanmethemoglobin is measured using a spectrophotometer.

Cyanmethemoglobin dilution

The standard procedure uses a $1:251$ dilution ($0.02\,mL$ blood in $5.0\,mL$ reagent).

Lipemia error

A source of error in hemoglobinometry that causes turbidity and falsely high results; it is corrected by using a plasma-reagent blank.