You are performing a spectrophotometry assay to quantify the activity of Ribulos

Question

You are performing a spectrophotometry assay to quantify the activity of Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCo), the most widely occurring enzyme on earth. This enzyme is involved in the first step of carbon fixation, so it is critical for photosynthesis in most higher plants. You want to know how fast this enzyme is degrading RuBP in a number of algae samples. In your assay, you include various salts and buffers, the substrate RuBP and 25 ml of algal extract that naturalliy contains RuBisCo. You begin the reaction and remove a new sample for the spec every minute. Recall that a Blank solution is a negative control for a particular experiment. What solution should you use to blank your spectrophotometer? Select one: a. Salts and buffers only b. The same solution as the reaction: all the same salts and buffers, the substrate RuBP, and 25 ml of algal extract that naturally contains RuBisCo Oc. All the same salts and buffers, 25 ml of algal extract that naturally contains RuBisCo, but NO RuBP d. All the same salts and buffers, the substrate RuBP, but NO algal extract e. Distilled water only

Explanation / Answer

Answer is C . A blank solution is used to caliberate the spectrophotometer. It consists of all the chemicals in the test sample except the analyte being detected. In this case analyte is ribulose bisphosphate as its rate of degradation is being determined. This is done in order to zero down any absorbance of light by constituents other than analyte. Salt , buffer, algal extract containing RuBisCo and the enzyme itself have the ability to absorb some light which can provide a false positive signal. We only want light absorption from our analyte to be detected. Caliberation with salt, buffer and algal extract containing extract will help in nullifying absorption from these constituents.

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