Bicohemical Monitoring of Diabetes Flashcards
What enzymes in chemical reactions are used to measure glucose levels in a glucometer?
Glucose oxidase and Hexokinase
Detection:
-Electrochemical: detecting movement of electrons by redox reactions
-UV absorbance: color change or choice of detectable UV wavelength
How do the 1st Gen Glucose Biosensors work?
Glucose Oxidase:
Oxidation of Glucose -> H2O2 is produced and oxidized yielding an electron -> e- detected
Oxidation: Gain of oxygen or loss of H+
Reduction: Loss of oxygen or gain of H+
Why can the efficacy of the monitor reduce over time?
Because H2O2 denatures the enzyme Glucose Oxidase
How do the 2ns Gen Glucose monitors work?
Hexokinase:
1. Glucose to Glucose-6-P
2. Oxidation of Glucose-6-P and reduction of NADP+ to NADPH (redox)
3. detection of NADPH or detection of UV absorbance of NADPH
What does Beers Law say?
UV absorbance is propotional to concentration
What does Selectivity in analytic chemistry mean?
Selectivity depends on possible interference from other compounds,
for Glucose oxidase: Ascorbic acid, creatinine (breakdown of creatine in muscle)
What chains are present in hemoglobin?
fetal: HbF -> 2 alpha, 2 gamma - 0.5%
embryonic: HbA 2 -> 2 alpha, 2 delta - 2.5%
in adults: HbA -> 2 alpha, 2 beta - 97%
-> 6% of hemoglobin A (HbA 1) is glycated (mostly Glucose)
Which type of hemoglobins is mostly glycated?
-> 6% of hemoglobin A (HbA 1) is glycated (mostly Glucose)
5%: HbA 1c
Where is Glucose attached to Hemoglobin A1c?
Mostly to the N-terminal Valin of ß-chains, small amount of N-terminal Valin of alpha-chain
Why is glycated hemoglobin mostly found in adults?
Because embryonic and fetal hemoglobin doesn’t have ß-chains
Where is Glucose attached to Hemoglobin A1c?
Mostly to the N-terminal Valin of ß-chains, small amount of N-terminal Valin of alpha-chain
Which step of the glycation is reversible/nonreversible
The first is a reversible reduction, and the last step is non-enzymatic and final -> stays until the protein is degraded (60 days)
What organic reaction describes the last non-enzymatic reaction in the glycation of hemoglobin?
The Maillard reaction: Reaction between sugar and protein = Glycation products
often in food: aromatic and favorable products: Maillard’s products
What drives the Maillard reaction?
Heat
non-enzymatic: just need the reactants sugar and proteins and heat
What is the lifespan of a red blood cell?
60-90 days
50% of the glycation reaction occurs in 30 days
40% between days 31 and 90
