Hematology Chapter 9 – Flashcards
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Hereditary nonspherocytic hemolytic anemia
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Hereditary deficiency of nearly every enzyme involved in glycolysis. A common result of these deficiencies is shortened RBC survival, known as __?
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Cation pumps
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Transmembranous cation gradient concentration proteins
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-maintenance of intracellular cationic electrochemical gradients -maintenance of membrane phospholipid -maintenance of skeletal protein plasticity -maintenance of functional ferrous Hb -protection of cell proteins from oxidative denaturation -initiation and maintenance of glycolysis -synthesis of glutathione -mediation of nucleotide salvage reactions
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Erythrocyte metabolic processes requiring energy:
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-O2 exchange -O2 binding to heme iron
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Erythrocyte metabolic process not requiring energy:
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facilitated membrane transport system
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How does plasma glucose enter the RBC?
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involves glucose phosphorylation, isomerization, and diphosphorylation --> fructose 1,6-biphosphate (substrate for aldolase cleavage) --> glyceraldehyde 3-phosphate (G3P)
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Explain 1st phase of glucose catabolism.
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G3P --> 3-phophoglycerate (3-PG) --> 1,3-biphosphoglycerate (1,3-BPG) --[dephosphorylated by phosphoglycerate kinase]--> ATP + 3-PG
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Explain 2nd phase of glucose catabolism.
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3-PG --[isomerized by phophoglyceromutase]--> 2-phosphoglycerate (2-PG) --[enolase]--> phosphoenolpyruvate (PEP) --[pyruvate kinase]--> ATP + pyruvate
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Explain 3rd phase of anaerobic glucose catabolism.
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Hexose Monophosphate
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detoxifies accumulated peroxide, oxidizes heme iron, proteins, and lipids.
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G6PD activity
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able to detoxify oxidative compounds and safeguard Hb, sulfhydryl-containing enzymes, and membrane thiols, allowing normally functioning RBCs to carry enormous quanitities of O2 safely
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G6PD deficiency
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Most common human RBC enzyme deficiency worldwide resulting in hereditary nonspherocytic anemia.
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Methemoglobin
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Hemoglobin with iron in the ferric state.
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methemoglobin reductase [cytochrome b5 reductase (cytob5r)]
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-Reduction of methemoglobin by NADPH is more efficient in the presence of ___? *acts as an intermediate electron carrier
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Rapoport-Luebering Pathway
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-generates 2,3-biphosphoglycerate -cell is put in ATP deficit by this diversion
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2,3-biphosphoglycerate (2,3-BPG)
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-regulates O2 delivery to tissues by essentially competing with O2 for Hb -when it binds, O2 is released, which enhances delivery of O2 to the tissues
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RBC deformability
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-property of a RBC to stretch undamaged up to 2.5 times their resting diameter as they pass through narrow capillaries and through splenic pores 2 um in diamter
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1. RBC geometry 2. Cytoplasmic (Hb) viscosity 3. Membrane elasticity (pliancy)
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RBC properties that contributes to deformability:
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Cholesterol
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-confers tensile strength to the lipid bilayer
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Acanthocytosis
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-results from deficiency in membrane enzymes that maintain the cholesterol concentration by regularly exchanging membrane and plasma cholesterol
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Target cell
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-In liver disease with low bile salt concentration, membrane cholesterol concentration becomes reduced. It results in this RBC appearance *plasma bile salt concentration affects cholesterol exchange
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Glycocalyx
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A layer of carbs whose net negative charge prevents microbial attack and protects the RBC from mechanical damage caused by adhesion to neighbouring RBCs or to the endothelium.
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Glycolipids
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-make up 5% of external half of RBC membrane -associate in clumps and support carb side chains that extend into plasma to form glycocalyx -antigens of ABO/Rh and Lewis blood group systems are made up of this
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-support surface carbs -serve as transport (disruption changes osmotic tension=rise in viscosity and loss of deforambility) and adhesion sites (change permits RBC to adhere to each other and vessels) and signaling receptors (signal tarnsduction) -skeletal anchorages (i.e. ankyrin) provide RBC membrane structural integrity
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What are some functions of transmembranous proteins?
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- a-spectrin - B-spectrin
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What are the principal skeletal proteins?
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Spherocytes
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-Too few vertical anchorages to maintain stability -The lipid membrane peels off in small blebs called vesicles, whereas the cytoplasmic volume remains intact. It generates this form of RBC
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Elliptocytes
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-membrane fails to rebound from deformation, and RBCs progressively elongate to form this RBC -causes a mild to severe hemolytic anemia
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Aquaporin 1
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a transmembranous protein that forms pores or channels whose surface charge create inward flow of water in response to internal osmotic changes
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Colloid Osmotic Hemolysis
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Pump machanism damage permits the influx of Na+, with water following osmotically. The cell swells, becomes spheroid, and eventually ruptures, spilling Hb. What is this phenomenon called?
