RBC Metabolism Flashcards
This will decrease the lifespan of a RBC
any changes to the shape and function of a normal RBC
RBC Plasma Membrane Constitutes of…
8% carbohydrates, 52% proteins, 40% lipids
Lipids of the RBC Plasma Membrane
- cholesterol
> amphipathic
> allows tensile strength, deformability at low temps, stability
> anchor other proteins - phospholipids
> fluidity
> elasticity
> hydrophilic head and hydrophobic tails
Effect of Liver disease to RBCs
- decreased membrane cholesterol so RBC present as ‘target’ cells
- cells more fluid w excess membrane that collapses and produces target cells
increased plasma membrane cholesterol
- incorporated into membrane
- rigid cells
- O2 carrying capacity is decreased
Proteins in the RBC Plasma Membrane
- integral: transmembrane proteins, vertical membrane structure, signal receptors, transport and adhesion sites, anchor bilayer to cytoskeleton
- peripheral: lateral or horizontal membrane stability, do not penetrate bilayer, alpha and beta spectrin
T or F. RBCs have a low SA:Vol ratio
F! High! This ensures efficient and constant rate of gas exchange
Increased MCHC (>360) leads to
- increased Hb viscosity
- compromises RBC deformability
- decreases life span
Causes of high MCHC
- anemias
- hereditary spherocytosis
- liver disease
- cold agglutinins
- sample interferences (lipemia, icterus)
- increased WBC counts
RBC processes that require E input
- maintenance of phospholipid membrane
- Hb function (ATP makes sure iron does not become oxidized)
- cell metabolism (no ATP input = no ATP generation = no ATP for cell function)
- prevention of cell oxidation
Embden-Meyerhof Pathway
- no mitochondria
- ATP by breaking down plasma glucose into ATP
- no glycogen storage; glucose enters freely through Glut-1 transmem protein
- net gain = 2 ATP
- anaerobic
Deficiencies in enzymes in Embden-Meyerhof pathway
lead to non-spherocytic anemia
Describe the Embden-Meyerhof Pathway
3 phases which utilizes three shunts:
- Hexose Monophosphate
- Methemoglobin Reductase
- Rapoport-Luebering
- these are important in preventing oxidative damage to cell and other essential by-products for transport and delivery
What happens to Rapoport-Luebering Pathway if acidic environment is present
- low 3-PG
- low 2-PG
so stop action of pathway to prevent entrance of 1,3-BPG into this shunt
- promotes 1,3-BPG to continue in the EMP to produce ATP
Hereditary Elliptocytosis
- defects in cytoskeletal proteins
- RBC fails to rebound from deformation
- RBC’s progressively elongate and form elliptocytes
Hereditary Spherocytosis
- defects in vertical support proteins
- loss of lipid membrane
- reduced membrane:cytoplasm ratio (SA:Vol ratio)
- cells are spherical and rigid
- decreased vol but normal conctn of Hb leads to increased MCHC values
- loss of central pallor
- dark, small RBC
Most common pathway defect
G6PD deficiency
without G6PD …
- cells cannot produce NADPH
- RBC vulnerable to oxidative damage
Most common inherited RBC enzyme deficiency, X-linked
G6PD deficiency
G6PD deficiency can cause …
- non-spherocytic anemia
- hlobin chain denaturation
- globin chains can precipitat out as HEINZ bodies
- oxidation damages components of cell membrane leading to eventual ell death
- extravascular hemolysis
G6PD def is exasperated by…
drugs, chemicals, fava beans
Pros of G6PD def
RBC more susceptible to oxidative stress = offers protection and kills malarial parasites
Pyruvate kinase def
- inherited autosomal recessive
- cells cannot complete glycolysis and generate adequate ATP
- RBC break down easily causing anemia in patients
- complications and patient symptoms depend on severity of diseases
- supportive therapy for patients
- burr or crenated cells peripheral blood smear
