Ch. 9 - Energy Metabolism and Membrane Physiology of the Erythrocyte Flashcards
Process that provides energy to the RBCs
Glycolysis
Average life span of RBCs
120 days
Disease where there is shortened RBC survival due to deficiencies in enzymes involved in glycolysis
Hereditary nonspherocytic hemolytic anemia
What are the intracellular levels sodium, potassium and calcium?
- Low sodium and calcium
- high potassium
What are the extracellular levels of sodium, calcium and potassium?
- low potassium
- high sodium and calcium
Main molecule that supplies the energy of RBCs
Glucose
What is the net gain of ATP with the Embden-Meyerhof pathway?
2 molecules of ATP
3 shunts/diversions in the glycolytic pathway to generate products that maximize oxygen delivery from several vantage points
- Hexose monophosphate pathway (HMP)/aerobic glycolysis/pentose phosphate shunt
- Methemoglobin reductase pathway
- Rapoport-Leubering pathway
What generally happens in the Hexose monophosphate pathway?
There is synthesis of glutathione that will reduce peroxide to water and oxygen. By detoxifying peroxide, the functional life span of the RBC is increased.
Molecule that is an essential requirement in the hexose monophosphate pathway. Without it, erythrocytes are vulnerable to oxidative reduction.
Glucose-6-phosphate dehydrogenase
What is the general purpose of the methemoglobin reductase pathway?
The pathway makes sure that the iron must be in the ferrous state to participate in the formation of heme.
What happens during the Rapoport-Leubering pathway?
2,3-bisphosphoglycerate regulates oxygen delivery to tissues by competing with oxygen for hemoglobin. Oxygen is released when 2,3-BPG binds which enhances delivery of oxygen to the tissues.
3 factors that affect RBC deformability
- geometry
- viscosity
- elasticity/plasticity/pliancy
Average volume of RBCs
90 fL
Average surface area of RBCs
140 um2
How many time can the RBCs be stretched without damage?
2.5 times their resting diameter
Normal range of mean cell hemoglobin concentration
32-36%
What is the relationship between hemoglobin concentration and viscosity?
Directly proportional; as hemoglobin concentration increases, viscosity rises
What are the percent composition of carbohydrates, proteins and lipids in the RBC membrane?
- 8% carbohydrates
- 52% proteins
- 40% lipids
Substances in the RBC membrane that reseals tears when the membrane is torn
Phospholipids
Substance in the RBC membrane that confers tensile strength to the lipid bilayer
Cholesterol
Substance that maintains the cholesterol concentration in the lipid bilayer by regularly exchanging membrane and plasma cholesterol
Membrane enzymes
2 phospholipids on the outer layer of the RBC membrane
- Phosphatidylcholine
- Sphingomyelin
2 phospholipids in the inner layer of the RBC membrane
- Phosphatidylserine (PS)
- Phosphatidylethanolamine
The only negatively-charged phospholipid
Phosphatidylserine
Phospholipid that redistributes (flips) to the outer layer during sickle cell anemia & thalassemia or in RBCs that have reached their 120 day life span
Phosphatidylserine
When does the “target cell” appearance of RBCs occur?
When there is low bile salt concentration which in turn lowers membrane cholesterol concentration
A layer of carbohydrates whose net negative charge prevents microbial attack and protects the RBC from mechanical damage caused by adhesion to the neighboring RBCs or to the endothelium
Glycocalyx
The glycocalyx is made up of ____________
Glycolipids
Aggregation of transmembranous proteins that provide RBC membrane structural integrity
Ankyrin/protein 4.1
The transmembranous proteins provide _________ membrane structure
Vertical
What is used to stain glycophorins?
Periodic-acid Schiff (PAS) dye
Indentification technique that distinguished 15 membrane proteins
Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) using Coomassie blue dye
2 principal skeletal proteins
Alpha-spectrin and beta-spectrin
Shape formed by the spectrins
Hexagonal lattice
How many triple helix repeats make up an alpha spectrin?
20 triple-helical repeats with 106 amino acids each
How many triple helix repeats make up a beta-spectrin?
16 triple-helical repeats of 106 amino acids each
Condition where the RBC membrane fails to rebound from deformation, and the RBCs progressively elongate to form visible eliptocytes which cause a mild to severe hemolytic anemia
Hereditary elliptocytosis (ovalocytosis)
A transmembranous protein that forms spores or channels whose surface charges create inward flow of water in response to internal osmotic changes
Aquaporin 1
A transmembranous protein that transports glucose without energy expenditure
Glut-1
Intracellular-to-extracellular ratio sodium
1:12
Intracellular-to-extracellular ratio of potassium
25:1
Normal range of calcium intracellularly
5-10 umol/L
Enzyme that increases the reduction rate of methemoglobin by NADPH
Cytochrome b5 reductase (cytob5r)
Regulates the concentration of Na and K, maintaining the normal intracellular-extracellular ratios
ATPase-dependent cation pumps
Condition where there is pump mechanism damage which permits the influx of Na, with water following osmotically. The cell swells, becomes spheroid, and eventually ruptures
Colloid osmotic hemolysis
Mechanism that extrudes Ca from the RBC
Ca2+ ATPase
Controls the function of Ca2+ ATPase; a cytoplasmic Ca2+binding protein
Calmodulin
