Biochem: Plasma, RBC, & WBC Chapters 52-54

Albumin

Which plasma protein accounts for roughly 60% of plasma protein by mass and is the principal determinant of intravascular osmotic pressure?

Albumin

Which plasma protein transports fatty acids, bilirubin, metal ions, and certain drugs?

Haptoglobin

Which plasma protein binds free hemoglobin released into the circulation and helps prevent damaging hemoglobin-derived precipitates in the renal tubules?

Ferritin

Which intracellular iron-storage protein can bind approximately 3000–4500 ferric iron atoms?

Transferrin

Which liver-synthesized plasma glycoprotein transports Fe3+ through the circulation?

Ceruloplasmin

Which major copper-containing plasma protein functions as a ferroxidase and oxidizes Fe2+ to Fe3+ during iron recycling?

Hepcidin

Which 25-amino-acid peptide is the chief regulator of systemic iron homeostasis and decreases iron absorption by causing ferroportin internalization and degradation?

Ferroportin

Which cellular iron-export protein is internalized and degraded after binding hepcidin?

Transferrin receptor 1

Which receptor is found on most cells and mediates cellular uptake of transferrin-bound iron through receptor-mediated endocytosis?

Transferrin receptor 2

Which transferrin receptor is found primarily on hepatocytes and intestinal crypt cells and functions mainly as an iron sensor rather than an importer?

DMT1

Which transporter moves Fe2+ from the endosome into the cytoplasm during the transferrin cycle?

HFE

Which MHC class I–like protein participates in sensing circulating iron and regulates hepcidin expression?

Iron response element

What RNA hairpin structure binds iron regulatory proteins to control translation of ferritin and stability of TfR1 mRNA?

Iron regulatory protein

What cytoplasmic protein binds iron response elements and reciprocally regulates ferritin and TfR1 expression according to intracellular iron levels?

Iron-deficiency anemia

What diagnosis is suggested by low ferritin, low serum iron, increased TIBC, decreased transferrin saturation, increased soluble transferrin receptor, and microcytic hypochromic RBCs?

Iron-deficiency anemia

A patient has fatigue and pallor with microcytic, hypochromic RBCs, serum ferritin below 15 μg/dL, serum iron below 30 μg/dL, and transferrin saturation below 10%. What is the diagnosis?

Anemia of inflammation

What type of anemia is described as microcytic and hypochromic, associated with increased hepcidin, and refractory to iron supplementation?

Hereditary hemochromatosis

What disorder is characterized by excessive intestinal iron absorption and accumulation of iron in tissues, commonly involving mutations in HFE?

Wilson disease

A patient has copper accumulation in the liver, brain, kidney, and RBCs, with decreased plasma ceruloplasmin. What disorder is described?

Wilson disease

Which disorder results from mutation of ATP7B, causing impaired biliary copper excretion and abnormal copper accumulation?

α1-Antiproteinase

Which major plasma serine-protease inhibitor neutralizes trypsin, elastase, and other serine proteases?

α1-Antiproteinase deficiency

A patient has emphysema associated with a ZZ genotype and low levels of a major plasma serine-protease inhibitor. What deficiency is suggested?

α1-Antitrypsin deficiency liver disease

What condition can occur in individuals with the ZZ phenotype because mutant α1-antiproteinase aggregates in the endoplasmic reticulum of hepatocytes?

α2-Macroglobulin

Which plasma protein uses a “bait” region and a conformational change to trap and neutralize a broad range of proteases?

Amyloidosis

What condition results from accumulation of insoluble protein aggregates rich in β-pleated sheet in interstitial spaces?

Primary amyloidosis

Which type of amyloidosis is typically associated with a monoclonal plasma-cell disorder and accumulation of immunoglobulin light-chain fragments?

Secondary amyloidosis

Which type of amyloidosis involves accumulation of serum amyloid A-derived fragments associated with chronic infection or cancer?

Familial amyloidosis

Which type of amyloidosis can result from accumulation of mutated transthyretin?

Immunoglobulin

What class of oligomeric glycoproteins consists of heavy and light chains and functions as antibodies?

IgG

Which immunoglobulin is the major antibody in the secondary immune response, crosses the placenta, fixes complement, and opsonizes bacteria?

IgA

Which immunoglobulin is the principal secretory antibody that prevents bacterial and viral attachment to mucous membranes?

IgM

Which immunoglobulin is produced first in the primary response, fixes complement, and serves as an antigen receptor on B cells?

IgD

Which immunoglobulin is found on the surface of B cells where it functions as an antigen receptor?

IgE

Which immunoglobulin mediates immediate hypersensitivity and contributes to defense against helminths?

J chain

Which polypeptide is associated with polymeric IgA and IgM?

Secretory component

Which component is present in secretory IgA but not serum IgA or IgM?

Fab

Which portion of an immunoglobulin contains the antigen-binding site?

Fc

Which portion of an immunoglobulin contains constant regions responsible for class-specific effector functions?

Hypervariable regions

Which regions of immunoglobulin light and heavy chains form the antigen-binding site and determine binding specificity?

Complementarity-determining regions

What are the hypervariable regions of immunoglobulins also called?

Hinge region

Which region of IgG provides flexibility to the Fab arms and facilitates binding to separate antigen molecules?

Combinatorial diversity

What mechanism generates antibody diversity by mixing and rearranging different immunoglobulin gene segments?

Activation-induced cytidine deaminase

Which enzyme converts cytidine to uracil and increases somatic mutation of immunoglobulin variable genes?

Junctional diversity

What mechanism of antibody diversity results from random addition or deletion of nucleotides when gene segments are joined?

Class switching

What process changes the immunoglobulin heavy-chain class while retaining the same antigen specificity?

Monoclonal antibody

What antibody is produced by an immortalized hybridoma cell line and targets a single epitope?

Hybridoma

What cell line is produced by fusing antigen-stimulated B cells with myeloma cells to generate an immortalized source of a monoclonal antibody?

Complement system

What humoral arm of the innate immune system consists of circulating zymogens activated through proteolytic cascades?

Classical complement pathway

Which complement pathway is triggered when an antibody-antigen complex activates C1?

Lectin complement pathway

Which complement pathway is initiated when mannose-binding lectin binds polysaccharides on a pathogen?

Alternative complement pathway

Which complement pathway involves spontaneous C3 activation and formation of a C3b:Bb complex?

Membrane attack complex

What complement complex is assembled from C5b through C9 and contributes to destruction of target membranes?

Mannose-binding lectin

Which complement-recognition protein binds mannose-rich polysaccharides on microbial surfaces?

Agammaglobulinemia

What immunodeficiency is characterized in the chapter by markedly impaired production of IgG and increased susceptibility to infection?

Autoimmune disease

What condition occurs when the immune system fails to distinguish host cells from foreign invaders and attacks its own tissues?

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Erythrocyte

What specialized blood cell is responsible for transporting oxygen and helping remove carbon dioxide?

Anemia

What condition is defined in the chapter as a deficiency in circulating hemoglobin below approximately 120–130 g/L?

Hematopoietic stem cell

What undifferentiated cell can self-renew and generate specialized blood-cell types?

Erythropoietin

Which kidney-derived glycoprotein hormone stimulates erythrocyte production in response to hypoxia?

Thrombopoietin

Which hormone directs myeloid progenitor differentiation toward platelet production?

Biconcave shape

What structural feature of erythrocytes increases surface-area-to-volume ratio and allows them to deform through narrow capillaries?

Glycolysis

What metabolic pathway provides ATP for mature erythrocytes because they lack mitochondria?

GLUT1

Which glucose transporter allows glucose to enter erythrocytes by facilitated diffusion and does not require insulin?

2,3-Bisphosphoglycerate

Which erythrocyte metabolite binds and stabilizes the T-state of hemoglobin?

2,3-BPG mutase

Which enzyme converts 1,3-bisphosphoglycerate to 2,3-bisphosphoglycerate in the RBC glycolytic shunt?

Carbonic anhydrase

Which erythrocyte enzyme rapidly converts CO2 to carbonic acid and facilitates transport of CO2 as bicarbonate?

Reticulocyte

What immature red blood cell retains some ribosomes, endoplasmic reticulum, mitochondria, and residual mRNA during its approximately 24-hour maturation?

Methemoglobin

What form of hemoglobin contains Fe3+ rather than Fe2+ and is unable to bind oxygen normally?

Cytochrome b5 reductase

Which enzyme transfers electrons from NADH to cytochrome b5 to reduce methemoglobin Fe3+ back to Fe2+?

Methemoglobinemia

A patient develops cyanosis after exposure to oxidizing substances such as nitrates or certain drugs. What condition involving excessive methemoglobin is suggested?

Glucose-6-phosphate dehydrogenase

Which X-linked enzyme provides NADPH through the pentose phosphate pathway and protects RBCs from oxidative stress?

G6PD deficiency

A patient develops hemolytic anemia after oxidative stress and has RBCs containing Heinz bodies. What enzymopathy is most likely?

Heinz bodies

What insoluble aggregates of oxidized hemoglobin form in RBCs during severe oxidative stress?

Glutathione

Which intracellular antioxidant must remain in its reduced form to protect RBCs from oxidative damage?

Hemolytic anemia

What type of anemia results from excessive destruction or lysis of red blood cells?

Sickle cell anemia

What hemoglobinopathy results from substitution of valine for glutamic acid at codon 6 of the β-globin gene?

Thalassemia

What group of disorders results from mutations affecting α- or β-globin synthesis and can cause hemolytic anemia?

Pyruvate kinase deficiency

What RBC enzymopathy reduces glycolytic ATP production and can impair the ability of erythrocytes to maintain ionic and water balance?

Paroxysmal nocturnal hemoglobinuria

What hemolytic disorder results from mutations in PIG-A affecting synthesis of GPI-anchored proteins?

Hereditary spherocytosis

A patient has hemolytic anemia, splenomegaly, and spherical RBCs caused by abnormalities involving spectrin or related membrane proteins. What is the diagnosis?

Hereditary elliptocytosis

What inherited disorder produces elliptically shaped RBCs due primarily to abnormalities involving spectrin or band 4.1?

Spectrin

Which major erythrocyte cytoskeletal protein forms an internal mesh that maintains RBC shape and flexibility?

Ankyrin

Which erythrocyte cytoskeletal protein binds spectrin to band 3 and anchors the cytoskeleton to the membrane?

Band 3 protein

Which transmembrane RBC protein exchanges chloride and bicarbonate across the erythrocyte membrane?

Glycophorin A

Which abundant transmembrane glycoprotein contains many O-linked oligosaccharides and contributes to the MN blood group system?

ABO system

What blood group system is based on genetically determined carbohydrate antigens on the erythrocyte surface?

H substance

What precursor carbohydrate structure is converted into A or B blood group substances?

A transferase

Which enzyme adds GalNAc to H substance to produce the A blood group substance?

B transferase

Which enzyme adds galactose to H substance to produce the B blood group substance?

Bombay phenotype

What blood group phenotype occurs in individuals with the homozygous hh genotype who cannot synthesize H substance and therefore appear type O regardless of A/B transferase genes?

Type AB

Which ABO blood type has both A and B antigens and neither anti-A nor anti-B antibodies, making it the universal recipient in the chapter?

Type O

Which ABO blood type lacks A and B antigens and has both anti-A and anti-B antibodies?

Platelet

What enucleated blood element contains mitochondria, dense granules, and α-granules and participates in hemostasis?

Dense granules

Which platelet granules contain Ca2+, ADP, and serotonin?

α-granules

Which platelet granules contain fibrinogen, fibronectin, platelet-derived growth factor, and von Willebrand factor?

Immune thrombocytopenic purpura

A patient has a low platelet count because antibodies bind the patient's own platelets, leading to their clearance by splenic macrophages. What is the diagnosis?

Von Willebrand disease

What inherited bleeding disorder results from impaired platelet adhesion to the endothelium rather than a reduced platelet number?

Bernard-Soulier syndrome

What inherited platelet disorder results from deficiency of glycoprotein Ib?

Glanzmann thrombasthenia

What inherited platelet disorder results from deficiency of the glycoprotein IIb/IIIa complex?

Hemolytic-uremic syndrome

An infant presents with progressive kidney failure, thrombocytopenia, and hemolytic anemia. What diagnosis is described in the chapter?