MLS 332 Unit 2

Function of Erythrocytes

transport oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs

Lifespan of an Erythrocyte

~120 days

Dimensions/Shape of an Erythrocyte

-biconcave disc

-7-8 mcM in diameter

-MCV= 80-100 fL

RBC Concentration Age Characteristic

highest at birth then gradually decreases

RBC Concentration Gender Characteristic

higher in males than females

RBC Concentration Location Characteristic

higher in high altitudes

Functions of RBC Membrane

-Special erythropoiesis receptors

-Regulates RBC metabolism

-Takes in vital components

-Release metabolic waste

-Balances exchange of ions

-Provides antigenic expression

-Responsible for strength & deformability

Erythrocyte Membrane Composition

~52% protein

~40% lipid

~8% carbohydrate

Erythrocyte Membrane Lipids

-Phospholipids

-Cholesterol

-Glycolipids

Erythrocyte Inner Membrane Phospholipids

PS, PI, PE

Erythrocyte Outer Membrane Phospholipids

PC, SM

Erythrocyte Membrane Integral Proteins

Glycophorins and transport proteins

Glycophorins

-integral proteins

-A,B,C

-Zeta potential

-RBC antigens

-Anchors skeletal proteins

Zeta Potential

degree of negative charge on the surface of a red blood cell

Transport proteins

-type of internal protein

- >100 types

-Band 3

Band 3

-intergral transport protein

-responsible for the chloride/bicarbonate exchange

-major binding site

-anchors skeletal proteins

Peripheral Proteins

-on the cytoplasmic side of membrane

-structural proteins

Horizontal Structural Proteins

support lipid bilayer

Vertical Structural Proteins

attach protein skeleton

Spectrin

-peripheral proteins

-α and β heterodimers

-interacts horizontally to the cell membrane

-responsible for spring-like deformability of RBC

Ankyrin

-Binds spectrin to Band 3

-Strengthened by band 4.2

Erythrocyte Deformability

-biconcave shape

-internal viscosity

-viscoelastic membrane

Which of the following RBC membrane component is responsible for spring-like deformability of the RBC and interacts horizontally to the cell membrane?

a. glycophorin c

b. spectrin

c. ankyrin

d. band 3

b. spectrin

Erythrocyte Metabolism

energy-dependent metabolic process are required to maintain cation pumps, hgb iron in the reduced state, and membrane integrity/deformability

Glycolytic Pathway Function

-provides RBC with ATP by breaking down glucose

-metabolizes ~90-95% of RBC glucose

Glycolytic Pathway Mechanism

-glucose is broken down lactate or pyruvate

-net gain of 2 ATP per 1 glucose

Hexose Monophosphate (HMP) Shunt Function

-provides NADPH and reduced glutathione (GSH)

-maintain hemoglobin in the reduced (functional) state

-safeguards vital cellular enzymes from oxidation

Raport-Leubering Shunt Function

-controls the amount of 2,3-BPG produced which in turn affects the oxygen affinity of hemoglobin

-regulates oxygen delivery to the tissues

Raport-Leubering Shunt Mechanism

Sacrifices the production of one of the 2 ATP molecules produced by glycolysis to make 2,3 BPG

Methemoglobin Reductase Pathway Function

-protects hemoglobin form oxidation by using NADH (from the glycolytic pathway) and methemoglobin reductase

-maintains methemoglobin levels at ~2% as opposed to 20-40% in its absence

Methemoglobin Reductase Pathway Mechanism

methemoglobin reductase and NADH reduce methemoglobin back to hemoglobin

Which erythrocyte metabolic pathway is responsible for controlling 2,3 BPG production and therefore controlling oxygen affinity within the cell?

a. glycolysis

b. hexose monophosphate shunt

c. rapaport-leubering shunt

d. methemoglobin reductase pathway

c. rapaport-leubering shunt

Erythrocyte Production Regulation

regulated by EPO

Erythropoeietin (EPO)

-thermostable, renal, glycoprotein hormone

-80-90% produced in kidneys

-<15% produced in the liver

-stimulates erythropoiesis

Erythropoiesis Release

release of EPO increases rate of bone marrow cell production/rate of release and releasee in response to tissue hypoxia

EPO Action

-EPO binds to EPO-R which initiates JAK/STAT pathway and CFU-E

EPO Cellular Effects

-prevents apoptosis

-increases erythropoiesis 5 to 10 fold

RBC Senescence

-decline in cellular enzymes, ATP production, and redox capabilities

-oxidative damage, inability to maintain osmotic equilibrium via cation pumps

-accumulation of IgG on RBC surface

-exposure of PS (inner phospholipid) on outer leaflet

Extravascular RBC Destruction

-located in spleen, bone marrow, and liver

-90% of all RBC destruction

Intravascular RBC Destruction

occurs in the bloodstream

Hemoglobin

highly specialized intracellular tetrameric protein

Hemoglobin Critical Values

<6.6 g/dL

Hemoglobin Subunits

2 alpha and 2 beta global chains and one heme molecule

Hemoglobin Structure

tetrameric molecule with 4 globin chains and one heme molecule held together by salt bonds, hydrophobic contacts, and hydrogen bonds

Heme

tetrapyrrole ring with ferrous iron in center

Ferrous Iron

Fe++

Ferric Iron

Fe+++

Each heme molecule binds with ______

1 oxygen molecule

Globin Chain

-amino acid chain responsible for function & physical properties of hgb

-changes hemoglobin stability and oxygen affinity if altered

-2 identical alpha and 2 identical beta chains

Ontogeny of Hemoglobin

type of hemoglobin is determined by the globin chains it is made up of

Adult Hemoglobins

Hgb A, Hgb A2, Hgb F

HbA Globin Chains

2 alpha ; 2 beta chains

HbA Reference Interval

> 95%

HbA2 Globin Chains

2 alpha ; 2 delta chains

HbA2 Reference Interval

1.5-3.7%

HbF Globin Chains

2 alpha ; 2 gamma chains

HbF Reference Interval

< 2%

Glycosylated Hemoglobin

-Hgb A1c

-3.5% normal

-7.5% diabetes

Which of the following hemoglobin types makes up >95% of hemoglobin in an adult?

a. HgbA

b. HgbA2

c. HgbA1C

d. Hgb F

a. HgbA

What is the globin chain structure of the main type of hemoglobin in adults?

a. 2 alpha ; 2 beta chains

b. 2 alpha ; 2 gamma chains

c. 2 alpha ; 2 delta chains

d. 2 alpha ; 2 epsilon chains

a. 2 alpha ; 2 beta chains

Oxygen Affinity

the ease at which hgb binds and releases oxygen

Oxyhemoglobin

-relaxed (R) structure

-HIGH O2 affinity

-hgb WITH bound oxygen

Deoxyhemoglobin

-tense (T) structure

-LOW O2 affinity

-hgb WITHOUT oxygen

Partial Pressure of O2 (PO2)

-measured in mmHg

-rate at which gases diffuses across membrane

Oxygen Dissociated Curve (ODC)

graph that explains the quantity of hemoglobin that will be saturated with oxygen at different partial pressures of oxygen

Hgb saturation and PO2 have a ____ relationship, meaning there is progressive binding of O2 to hgb.

sigmoidal

ODC Left Shift

-decreased H+

-decreased CO2

-decreased temp

-decreased 2,3-BPG

HIGHER AFFINITY = O2 BINDS EASIER

ODC Right Shift

-increased H+

-increased CO2

-increased temp

-increased 2,3-BPG

LOWER AFFINITY = O2 RELEASES EASIER

Allosteric Property of Hemoglobin

-structure and function are affected by other molecules

Hemoglobin and 2,3-BPG

2,3-BPG produced by Rapaport-Leubering Shunt causes a decrease of O2 affinity which encourages release of O2 to tissues

What property of oxygen is responsible for the rate at which it diffuses across cellular membranes?

a. pH

b. partial pressure

c. allosteric properties

d. affinity

b. partial pressure

Which of the following would shift the oxygen dissociation curve to the right (increases release of oxygen to the tissues/decreases oxygen affinity)?

a. decreased H+

b. decreased CO2

c. decreased temperature

d. increased 2,3-BPG

d. increased 2,3-BPG

Extravascular Hemolysis

-90% of hgb destruction

-located in spleen, liver, bone marrow

-done by macrophages

-detected by increased urine/fecal urobillinogen and/or unconjugated bilirubin in plasma

Intravascular Hemolysis

-10% of hgb destruction

-occurs in blood vessels

Intravascular Hemolysis Laboratory Detection

-Hemoglobinuria

-Hemosiderinuria

-Hemoglobinemia

-Methem

oglobinemia

-Decreased haptoglobin/hemopexin

-Increased unconjugated bilirubin

-Increased LDH (lactate dehydrogenase)

Haptoglobin

binds free hgb in blood

Methemoglobin

-ferric iron (Fe3+)

-produced by loss of reducing enzymes, globin chain mutations, toxic substances

-cyanosis

-dark brown blood

-non-functional hgb

Sulfhemoglobin

-sulfur + hemoglobin

-environmental exposure

-greenish blood

-non-functional hgb

Carboxyhemoglobin

-carbon monoxide and hgb

-200x affinity for carbon monoxide compared to oxygen

-cherry-red blood

-non-functional hgb

Mean Corpuscular Volume (MCV)

-correlates to the SIZE of RBCs

-calculated by (hematocrit/RBC count)x10

-about 80-100 fL

Mean Corpuscular Hemoglobin (MCH)

-about 28-34 pg

-calculated by (hemoglobin/RBC count)x10

Mean Corpuscular Hemoglobin Concentration (MCHC)

-correlates to HEMOGLOBINATION

-about 32-36 g/dL

-calculated by (hemoglobin/hematocrit)x100

RDW-CV

RBC distribution width

>15 = anisocytosis

<15 = no anisocytosis

Poikilocytes

Change in RBC SHAPE

Anisocytosis

change in RBC SIZE

RBC Size Assessment

compare to small lymphocyte nucleus and MCV

RBC Hemoglobination Assessment

-assess diameter of central pallor and MCHC

Poikliocytosis Terms

1-3 = few

4-6 = moderate

> 6 = many

Anisocytosis Terms

slight

moderate

marked

Would a macrocyte (a larger than normal RBC) be considered a poikilocyte?

a. yes

b. no

b. no

What word best described a RBC whose central pallor is greater than 1/3 the diameter?

a. normochromic

b. hypochromic

c. spherocytic

b. hypochromic

Which of the following poikilocytes is the result of increased surfac area-to-volume ratio?

a. acanthocyte

b. codocyte

c. echinocyte

d. spherocyte

b. codocyte

A drepanocyte (sickle cell) can be seen in iron deficiency anemia.

a. true

b. false

b. false

What is the name of the RBC change in which increased plasma proteins cause the red blood cells to "stick together" in a stack of coins formation?

a. agglutination

b. rouleaux

c. Babesia

d. clumping

b. rouleaux

Rheostat

used to adjust light preference

Condensor

up for stained and down for unstained

Par focal

when one lens is in focus, the other lenses will also have the same focal length and can be rotated into position without further major adjustment.

Par objective

when switching from one objective to the next, the image that was in the center of the field should remain in the center of the field

Azure (Methylene Blue)

purplish basic dye that binds acidic groups like DNA and RNA

EosinY

reddish acidic dye that binds basic components like hemoglobin