Step 1. Graph the calibration curve relating absorbance at 520 nm to glucose concentration. Fit a line function to the measured data points applying regression analysis with r2 > 0.80 (refer Calculations in Experiment 1).
Step 2. Calculate concentration of total reducing sugars (C) in the plant extract expressed as glucose equivalent concentration. Consider absorbance at 520 nm (A520) from experimental tubes and extinction coefficient (e) obtained from linear regression:
C (mM) = (A520 x e) x 2 (tube 6) or C (mM) = A520 x e (tube 7) Observations
Compare total carbohydrate and total reducing carbohydrate contents in the extract and calculate the relative participation of reducing carbohydrates referred to total carbohydrate content.
Experiment 12: Starch
Addition of an adequate quantity of KI to a starch solution (weakly acid) and dilute hydrogen peroxide leads to the formation of a blue starch-iodide complex. This complex can be detected at 620 nm (Chinoy, 1939).
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