Structure of RBCs Flashcards
What is the Bombay phenotype?
A person that has an O blood type, regardless of the alleles present at the I loci. This is due to h/h or O/h genotype that prevents mutation of an intermediate needed to generate A or B antigens
RBCs do not adhere to vessel walls or other RBCs. How is this possible?
Due to the presence of glycophorin on the outer membrane, which gives RBCs a negative charge
The pentose phosphate pathway is a shunt of glycolysis. How is this pathway utilized by the RBC?
The PPP generates NADPH, which the RBC needs to maintain stores of reduced glutathione. Glutathione is used to detoxify ROS and prevent oxidation of hemoglobin to metehemoglobin.
This protein is present on young RBCs to prevent phagocytosis, but is lost with aging.
CD47
Rh (+/-) is determined by the presence/absence of what antigen?
D antigen - contributes to membrane stability
True/False. Scramblases require ATP for activation.
False. Flipases & flopases require ATP. Scramblases require Ca2+/
This pathway is a shunt of glycolysis that accounts for over 65% of an RBC’s ability to reduce methemoglobin to hemoglobin.
Methemoglobin Reductase/ Cytochrome b5 Reductase
Glycophorin is sometimes referred to as a decoy receptor. What does this mean?
The protein serves as a receptor for some pathogens; however, the pathogen cannot infect or replicate inside the RBC. The pathogen is essentially stuck and the infected RBC is removed by the spleen.
The H gene is responsible for the H antigen, which is present on all RBCs. The I gene has three potential alleles. What are they?
A allele - N-aceytlgalactosamine transferase
B allele - galactose transferase
O allele - frameshift mutation with no functional protein
These alleles and their encoded proteins are responsible for blood type.
What is the role of alpha and beta spectrin?
Cytoskeleton proteins that form antiparallel dimers that provide horizontal stability to the RBC and contribute to deformability
Bone marrow is primarily responsible for erythropoiesis in adults. Where does erythropoiesis take place in the developing fetus?
Yolk sac, spleen, liver
Phospholipids of the RBC membrane are distributed asymmetrically. What is the effect of the loss of this asymmetry?
Loss of asymmetry indicates an aging or abnormal RBC. These RBCs are detected by the spleen and destroyed.
True/False. RBCs have a biconcave disk shape that provides a large area-to-volume ratio for gas exchange and deformability.
True - enhances gas exchange and survival under various pressures
Glucose enters RBCs through the insulin-independent GLUT1. How do RBCs generate ATP?
Anaerobic glycolysis
This RBC defect is caused by a spectrin mutation that causes loss of horizontal stability and the progressive elongation of RBCs.
Hereditary Elliptocytosis
What two complexes are responsible for anchoring the RBC membrane to the cytoskeleton?
Ankyrin complex, actin junctional complex
What is a reticulocyte?
The final immature form of an RBC that is released by bone marrow. They lack many organelles and a nucleus and mature in the blood to become a RBC.
This RBC defect is caused by a mutation to a protein in the ankyrin complex that causes loss of vertical stability.
Hereditary Spherocytosis - mutations to Band3, ankyrin, or spectrin that cause RBCs to become spherocytes without deformability
The Rapoport-Leubering Pathway is a shunt of glycolysis. What is the product of this pathway and its effect on oxygen delivery to cells?
Produces 2,3-BPG, which reduces hemoglobin’s affinity for O2 and promotes O2 delivery to tissues
These proteins bind to the GPI anchor on RBCs to prevent complement activation.
CD55 & CD59
