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Biochemistry- Unit Three
Erythrocyte (T Pierce)
23
Medical
Post-Graduate
05/04/2009

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Cards

Term
Structure of RBC
Definition
  • biconcave disc
    • generates more surface area than sphere
  • mean corpuscular volume (MCV)- 87 cubic microns
  • diameter- 7 microns
  • major content is Hb
    • Mean Corpuscular Hb Conc. (MCHC) of 33% (very concentrated solution of Hb)
    • MCH- how much Hb is in one RBC (absolute number) is 30 picograms/cell
Term
RBC count definition
Definition

how many RBC's in a given volume of blood (average value = 5-5.5 x 10^-12 cells/L)

 

Female count is usually lower than male.

Term
Difference btw plasma and serum
Definition
  • plasma- has clotting factors
  • serum- no clotting factors
Term
Describe the gradation of centrifuged blood
Definition
  • at top, you will see the plasma or serum
  • at bottom, you will see packed cells

If you measure volume of packed cells over total volume, you find hematocrit.

Term
How is Hb concentration determined
Definition

lyse the red blood cells and see the amount of Hb released in sample of blood

(average 16 grams/deciL)

Term
Function of RBC
Definition
  • carry molecular oxygen from the lungs to the peripheral tissue via protein Hb
  • bind CO2 and take it to the lungs
  • buffer (transport of CO2 in plasma as bicarb.)
Term
Driving force of binding of oxygen to Hb
Definition
partial pressure of oxygen (dont forget oxygenated Hb is a stronger acid than deoxygenated)
Term
Mechanism of formation of meth Hb
Definition
  • Hb-O2 dissociates to form superoxide anion and met-Hb
Term
Mechanism of converting met-Hb to Hb
Definition
  1. Met Hb and cyc b5 (carry ferrous) goes to Hb via Met Hb reductase
    1. cyc b5 (carrying ferric at the end of reaction) converted back to ferrous form via cyc b5 reductase (requires oxidation of NADH)
Term
Mechanism of inactivating superoxide anion formed by making met-Hb
Definition
  1. 2 superoxide anions and water produces oxygen and hydrogen peroxide via superoxide dismutase
  2. 2 hydrogen peroxides generates oxygen and 2 waters via catalase (hemeprotein)

Superoxide dismutase is in almost ALL cells.

Term
Effect of oxidant on plasma membrane
Definition
  • oxidant can oxidize the double bond in polyunsaturated fatty acids found in the membrane to a lipid peroxide
  • peroxides will break down to form free radicals
    • if this is not stopped, chain reactions that cause loss of membrane integrity

 

Term
Structure and functino of tocopherol (Vit. E)
Definition
  • structure- has a very long isoprenoid side chain with two connected ring structures
  • function
    • in reduced form, serves as antioxidiant (reducing agent) and inactivate oxidants (reduce it to alcohol) non-enzymatically
    • produces oxidized form of Vit E
Term
Compounds that can reduce vitamine E
Definition

vitamin C

glutathione

Term
Structure and function of glutathione system reducing vitamin E
Definition
  • tripeptide (glu, cys, gly)
  • SH group of Cys supplies reducing equivalents and its oxidized to the disulfide
  • function- reduce Vit E under non enzymatic conditions
Term
Function, location of glutathione peroxidase
Definition
  • location- can be associated with the membrane or in the cytosol
  • function (requires sellinium)
    • catalyze reduction of lipid peroxides using glutathione as reducing agent
Term
Function and structure of glutathione reductase
Definition
  • structure- flavoprotein
  • function
    • catalyze reduction of oxidized glutathione into reduced form (now it can eliminate lipid peroxides)
    • oxidizes NADPH to NADP (NEED HMG SHUT TO KEEP THIS RXN GOING)

 

Term
Mechanism of RBC maintaining ionic balance
Definition
  • w/o balance, cell will swell or shrink
  • maintained via ion pumps
    • Na/K pump (translocase)
      • uses half of ATP generated by RBC
    • ATP production via substrate level phosphorylation steps of glycolysis     (3 PG kinase and pyruvate kinase)
Term
Sequence of Rapoport Luebering Shunt
Definition
  1. 1,3 BPG goes to 2,3 BPG via mutase
  2. 2,3 BPG goes to 3-PGA via phosphatase
Term
Describe role of HMG Shunt in production of glycolytic intermediates
Definition
  1. oxidative pathway will produce the NADPH needed for glutathione reductase to form reduced glutathione and Ru-5P
    1. NADPH via G6PDH and 6PGDH
    2. can speed up to meet the need of glutathione reductase
  2. Ru-5P uses non oxidative pathway to form F6P via transketolase, transaldolase, and transketolase again
Term
Enzyme deficiencies that cause hemolytic anemia and how they kill RBCs?
Definition
  • G6P dehydrogenase (no NADPH for glutathione reducatse, so the cell is killed by oxidants)
  • pyruvate kinase (ATP cannot be provided to translocase needed to maintain ionic balance
Term
RBC values for patient with G6P DH deficiency (these values are indicative of any hemolytic anemia)
Definition

decrease RBC count

decrease Hb conc.

decrease Hct

normal MCV

normal MCHC

normal MCH

 

nothing wrong with volume or Hb in RBC

Term
classifications of anemia and their definitions
Definition
  • normocytic normochromic
    • volume normal
    • color of RBC normal
  • microcytic hypochromic
    • low MCV, MHC
    • not much color (usually when RBC's are small, there is not much color to them) 
  • macrocytic normochromic
    • high MCV/MHC
    • normal color to RBC

Based on volume

Term
RBC values of PK deficiency
Definition

Normocytic normochromic anemia

  • decrease RBC count
  • decrease Hb conc.
  • decrease Hct
  • normal MCH, MCV
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