Red Blood Cells Flashcards
How is CO2 transported in the blood?
Converting it into freely soluble HCO3- via carbonic anhydrase
How are fatty acids transported in the blood?
Serum albumin
How are triglycerides transported in the blood?
Lipoproteins
What are the formed elements of blood?
Sedimenting portions RBCs Platelets WBCs
What is the major protein in blood?
Albumin
What are the major cellular components of blood?
RBCS then platelets then WBCs
What does a mature erythrocyte NOT contain?
Nucleus Ribosomes Mitochondria
What causes RBC crenation?
Depletion of ATP
What causes RBCs to be called echinocytes?
Entry of large amounts of calcium ions resulting in a spiky appearance.
What causes RBCs to be called spherocytes?
Loss of spectrin scaffolding results in a spherical shape
How do RBCs make ATP?
Anaerobic glycolysis
What metabolic processes do RBCs need ATP for?
Maintenance of Ca levels Maintenance of Na/K gradients Creation of 2,3-DPG
How do 2,3-DPG levels affect RBCs?
Affects the binding of oxygen to hgb
Describe the role of Methemoglobin reductase (aka diaphorase)
An enzyme that reduces ferric (Fe3+) methemoglobin to Fe2+ with the help of NADH as a cofactor
What forms as a result of an accumulation of denatured methemoglobin?
Heinz bodies
What does reduced glutathione (GSH) do? What maintains its reduced state?
Protect the cell from oxidants (esp H2O2) Maintained by NADPH + G6PD (enzyme)
In a healthy person, what percentage of circulating RBCs are reticulocytes? How is this value used clinically?
2%, Reticulocyte index used to diagnose anemia
What physiologic level stimulates erythropoietin production?
Low tissue pO2 and low pH
Describe heme.
A porphyrin ring structure containing iron which binds oxygen.
In each hemoglobin molecule there are ___ heme groups, ____ iron molecules, and ____ oxygen-binding sites.
4, 4, 4
What is the primary source of iron in newly synthesized RBCs?
Recycled iron from degraded RBCs
How is iron transferred in the blood?
Transferrin
How is iron stored?
Ferritin or hemosiderin proteins
What is intravascular hemolysis?
Destruction of freely-circulating RBCs in the blood. Usually a response to transfusion reaction of toxins.
Where are RBCs normally destroyed removed?
In the spleen when they are unable to deform through small pores.
Liberated hemoglobin after lysis of RBCs in free circulation is picked up by _______.
Haptoglobin
What is hemoglobinuria and what causes it?
Hgb in urine caused by free hemoglobin excess of haptoglobin capacity and by the renal tubule capacity to filter.
What are the steps of heme breakdown?
- Porphyrin ring broken down into bilirubin via release of CO 2. Bilirubin in plasma binds to albumin 3. Bilirubin is conjugated with glucuronic acid in liver 4. Bilirubin glucuronide is secreted into the bile/GI tract 5. Converted to urobilinogen by GI tract bacteria
What is the most common cause of anemia?
Low RBC production due to iron deficiency
What are the causes of anemia?
- Iron deficiency 2. Vit B12 deficiency 3. Folic acid deficiency 4. Bone marrow disease 5. Defective Hgb synthesis 6. Inadequate erythropoietin
What is pernicious anemia?
Vit B12 deficiency from failure of parietal cells in the GI tract to produce intrinsic factor needed to absorb B12.
What is a typical form defective hgb?
Thalassemia – alpha and beta chains are made in disproportionate amounts.
What are the components of hemoglobin?
alpha and beta chain, porphyrin ring, heme
Marrow has the capacity to expand its rate of production of red cells by a factor of ___.
6
What is hereditary spherocytosis?
Membrane defect causes spherical and fragile RBCs. Treated by removing the spleen
What causes sickle cell anemia?
Single glutamic acid residue in Beta chain replaced by valine
What is Hereditary glucose-6-phosphate deficiency?
Hexose monophosphate shunt has low activity so little NADPH/reduced glutathione is produced. RBCs become sensitive to oxidizing agents
What blood type is a universal donor?
O
What blood type is a universal acceptor?
AB
What is autoimmune hemolytic anemia?
Antibodies attack a patient’s own cells causing agglutination.
What do Rh-positive blood cells express?
D antigen
What is erythroblastosis fetalis?
Attack of a 2nd Rh+ fetus in an Rh- mother (she would have made Rh IgG antibodies with a first Rh+ pregnancy/fetus)
What is the most common cause of anemia?
RBC production too slow due to insufficient iron levels
What are the causes of anemia?
- Iron deficiency 2. Vit B12 deficiency 3. Folic acid deficiency 4. Bone marrow disease 5. Defective Hgb synthesis 6. Inadequate erythropoietin
Glucose can enter RBCs ______ and ______, due to the _______.
Freely and easily (i.e. without special transporter) due to the concentration gradient.
What effect does 2,3 DPG have on hgb?
Decreases the affinity for oxygen (thus often seen in high levels in somenoe who has been at high altitudes)
At what stage of blood cell production/manufacture is hemoglobin made?
Normoblast
What are 2 clinical indicators of an intravascular hemolytic event?
Decreased haptoglobin in blood and hemoglobinuria (hgb in blood)
