[BCHEM] BLOOD GENERALITIES & RBC METABOLISM

transport, regulate, and protection

What are the major functions of the blood

red blood cells, platelets, white blood cells, and plasma

What are the four main components of the blood

hemoglobin, heme protein

This is the principal determinant of blood color, attributed to the presence of oxygen bound to which protein

planar structure, bright red

oxygen binds with the heme iron to create (this particular structure of hemoglobin) and appears as what (color)

non-planar stucture

The blood darkens when deoxygenated and creates which kind of stucture

Infants and neonates

Volume of Blood in

1) Infants and neonates 2) Adults

Males

Volume of Blood in

1) Males 2) Females

Serum

Which liquid portion when centrifuged does not contain anticoagulants?

Plasma

Which liquid portion when centrifuged contain anticoagulants, which prevents clotting of blood?

as a fibrin clot

The formed elements in serum are seen as which structure on top of the centrifuged whole blood?

they are easily separated and still suspended (due to anticoagulants added)

What is the characteristic of the formed elements in the plasma that differs from serum?

red blood cells

What are the heaviest/most dense elements in the blood that make up the majority of the formed elements?

Buffy coat

This is a thin white, middle layer of a centrifuged whole blood

WBC, Platelets

Buffy coat contains which elements?

plasma (55%) and formed elements (45%)

In the circulation, whole blood is composed of

fibrinogen

Serum is only formed during blood extraction when clotting factors, specifically ( ) are removed from plasma

Water (majority), Solutes (Organic, and Inorganic compounds)

Composition of the plasma of the whole blood in the circulation?

Hematopoiesis

This refers to the synthesis of blood cells

hematopoietic stem cells

All formed elements from blood have a common precursor derived from

bone marrow

These cells migrate from sites of hematopoiesis to reside in which structure

Cytokines

These are a subtype of growth factors and are cell-signaling molecules that mediate and regulate immunity, inflammation, and hematopoiesis

JAK-STAT Pathway

Most of the cytokines are recognized by the receptors which activate which pathway?

phosphorylated

Janus Kinases (family of tyrosine kinases) are usually active when in this state

dimerization and activation of JAKs

Step 1 in JAK STAT Pathway involves cytokine binding to receptors initiating which processes that favors phosphorylation of JAK tyrosine residues

binding of additional signal transduction molecules to the STAT

Step 2 in JAK STAT Pathway involves JAK dimerization and phosphorylation that promotes

gene transcription

Step 3 of JAK STAT Pathway: Binding and phosphorylation of STAT promotes its dimerization and its translocation to the nucleus, which then activates?

F; promote proliferation

T/F: Activation of gene transcription would then inhibit proliferation of specific cell lineages from the hematopoietic stem cells

Silencer of Cytokine Signaling (SOCS) proteins (4&5)

What are the negative regulators of the JAK-STAT pathway that may either bind to the phosphorylated receptors or bind to the JAKs itself and inhibit them

common myeloid progenitor cells

Hematopoietic stem cell proliferation & differentiation produce?

Stem cell factor (SCF) and Granulocyte-monocyte colony-stimulating factor (GM-CSF)

Hematopoietic stem cell proliferation & differentiation into common myeloid progenitor cells are stimulated by

RBCs - erythropoietin (EPO)

Platelets - thrombopoietin

Granulocytes and monocytes - Stem cell growth factor (GM-CSF + IL-5,6)

Myeloid progenitor cells then differentiate into:

RBCs by

Platelets by

Granulocytes and monocytes by

Common Lymphoid Progenitor cells

HSCs also form this lineage that eventually formsi B and T lymphocytes

Hematocrit Level

This refers to the volume of erythrocytes compared to the total blood volume (proportion of blood by volume consisting of RBC)

T

T/F: Hct level is directly proportional to the RBC count

Hemoglobin

This represents the protein component within each RBC and delivers oxygen to the organs and tissues; carries CO2 to lungs

Anemia

This occurs when Hgb concentration is below normal values

Mean Corpuscular Volume (MCV)

Red cell size is measured by?

NV: 80-100 fL

Normal value and Formula of MCV

Mean Hemoglobin Concentration (MCHC)

Hemoglobin concentration is measured by

NV: 32-36 g/dL

Normal value and Formula of MCHC

heme iron from animal foods

Which is better absorbed, non-heme iron from plant-based iron or heme iron from animal foods?

Ferroportin

These are proteins within the intestinal cells that will facilitate the reabsorption of iron

Transferrin

This protein carries iron around the circulation because iron in its ferrous form is toxic

Ferritin and Hemosiderin

These proteins bind with storage iron (storage form) will give it back to transferrin to be delivered to the bone marrow if needed for hemoglobin synthesis

Hephaestin

Copper-containing protein in the intestinal cells that also assists in the reabsorption of iron

ferroxidase activity

Why does ferroportin require hephaestin

oxidation of ferrous (Fe2+) to ferric (Fe3+)

Ferroxidase activity of hephaestin with ferroportin will facilitate which process for proper transport of iron for heme synthesis, allowing it to bind to transferrin

Ceruloplasmin

Major Cu++ carrier protein in blood that facilitates transport of Cu++ and also has ferroxidase activity

Copper Deficiency

This condition results into decrease of iron transport → iron accumulation in tissues

Hephaestin and Ceruloplasmin

Recall: What are the two proteins that have ferroxidase activity?

Coenzyme in the synthesis of heme, particularly in the enzyme aminolevulinic acid (ALA) dehydratase to produce porphobilinogen (PBG)

Folic Acid (Vit B9), Cobalamin (Vit B12)

These are essential for DNA synthesis and critical in the synthesis of new cells, including the RBCs

proerythroblast

EPO will stimulate synthesis first ( ) which also marks the start of hemoglobin production

erythroid committed precursors

In erythropoiesis, multipotent (common) myeloid progenitor cells commit to differentiate into

Reticulocytes and Pyrenocytes

Eventually the erythroblast will lose its nucleus and some organelles forming two daughter cells

T

T/F: Reticulocytes retain their capacity to synthesize polypeptides (eg. globin) because they have some ribosomes and mRNAs

F; Devoid of organelles and are unable to reproduce by itself and thus requires erythropoietin stimulation for synthesis of new RBCs

T/F: Mature erythrocytes contain organelles and therefore can reproduce by itself

Hemoglobin

What comprises 95% of the intracellular protein of red blood cells

Unique RBC cytoskeletal network enables it to fold over and squeeze through

The RBC membrane is strongly flexible and has reversible deformation due to which characteristic?

intracellular hemoglobin concentration

Viscosity of the cytoplasm of RBC is dependent on?

Phospholipids, Sphingolipids, Cholesterol, Integral membrane proteins

Lipid bilayer of RBC includes

Band 3, Glycophorins

What are the integral membrane proteins found in the lipid bilayer of RBC

tropomyosin-tropomodulin junctional complexes

Cytoskeleton of RBC, which consist of spectrin tetramers, is connected to actin via

Band 3

Cytoskeleton of RBC is tethered to the lipid bilayer through this protein at the spectrin-ankyrin binding sites

Adducin

This forms bridge between RBC bilayer and cytoskeleton

Accumulate Oxidative Damage

This reason of RBC Aging is caused by cycle of gas exchange and exposure to extrinsic chemicals which accumulates in the proteins within RBC

Cytoskeletal Damage

This reason of RBC Aging is due to osmotic swelling and shrinkage as well as gradual loss of surface area → decreases deformability and repetitive deformation

Absence of organelles

Reason why RBC is unable to repair cytoskeletal proteins and unable to synthesize new hemoglobin

Spleen and liver; macrophages

Aged RBCs are removed in these organs by which cells?

Hemoglobin components are further broken down, recycled, or metabolized into

Globin

Protein portion of hemoglobin that is broken down into amino acids and is sent back to bone marrow for the production of new RBCs

T

T/F: Recycled Iron is stored in the liver or spleen as ferritin and hemosiderin and is carried by the bloodstream by transferrin to the bone marrow

Biliverdin

Heme is degraded into this green pigment that will eventually be converted to bilirubin

Bilirubin

Degraded product of heme that appears as a yellow pigment and the discoloration often associated in cases of jaundice

albumin

Bilirubin binds to this protein to travel via bloodstream to the liver for bile production

urobilinogen and stercobilin

In the large intestines, bilirubin is broken apart from bile by bacteria and converts it to

urine

In the kidneys, bilirubin and other related byproducts (urobilin) are eliminated through

Biliverdin

This degraded component of heme is responsible for the dramatic colors associated with bruising

T

T/F: Body assumes a yellow-tinged color if you block bilirubin before or after the liver

no mitochondria

Reason why mature RBCs have no TCA cycle, ETC, β-oxidation pathway, No oxidative phosphorylation

No nucleic acid and protein synthesis

What are the consequences of RBC having no nucleus and ribosomes?

Maintenance of electrolyte gradient, synthesis of glutathione, maintenance of ferrous (Fe2+) state, and maintain the biconcave shape of RBCs

Mature RBCs require energy to maintain several functions

GLUT-1 transporter

Glucose is taken up by the RBC via

high affinity, NOT affected by insulin

GLUT-1 transporter has high/low affinity glucose and is/not affected by insulin

Glycolysis (EMP) - anaerobic; net gain of 2 ATP

Major utilization of the glucose supply of RBC and what is its net gain of ATP

Hexokinase (Step 1), Phosphofructokinase (Step 3)

Two ATP-consuming steps of the Preparatory Phase of Glycolysis

Phosphoglycerate kinase and Pyruvate kinase

Two ATP-generating steps of the Payoff Phase of Glycolysis

Lactate Dehydrogenase, G3PD step

This reduction of pyruvate to lactate through this enzyme subsequently regenerates NAD, which can be reutilized in this step and in turn generates NADH

Triosephosphate Isomerase

Important enzyme in EMP that exhibits the highest glycolytic enzyme activity to isomerize DHAP to G3PO4 → enter the payoff phase

G3PO4 dehydrogenase

Transforms G3P to 1,3-BPG with NAD as a cofactor (which comes from the conversion of pyruvate to lactate via LDH)

1,3-BPG (intermediate to 2,3-BPG)

Products of EMP that serves as a regulator (regulatory intermediate) of oxygen affinity to hemoglobin

NADH

Products of EMP that converts iron to its functional ferrous state

Rapoport-Luebering Shunt

Unique branch of the glycolytic pathways seen in mature RBCs

Rapoport-Luebering Shunt generates and dephosphorylates 2,3-bisphosphoglycerate (2,3-BPG) via this enzyme

Isomerize 1,3-BPG to 2,3-BPG

Mutase activity of BPGM by bisphosphoglycerate mutase

Hydrolysis of 2,3-BPG to 3-PG (→ reenter the main glycolytic pathway)

Phosphatase activity of BPGM by bisphosphoglycerate phosphatase

2,3-BPG

This facilitates the supply of oxygen to the tissues by binding to hemoglobin

R-state

When hemoglobin is deoxygenated, the equilibrium is driven to this state in which majority of O2 will attach to Hgb (oxygen loading)

oxygen unloading (decreases O2 affinity to Hgb)

In the presence of 2,3-BPG, it binds to the center pocket of the 2 beta-globin chains of Hb → stabilizes hemoglobin in the T-state, which favors?

GSH Reductase

Enzyme to reduce GSSG into its sulfhydryl form (GSH) through disulfide cleavage