Please help me, I am deeply confused in this class and trying so hard to underst

Question

Please help me, I am deeply confused in this class and trying so hard to understand. Please give detailed answers. I know some of these might be confusing but your help will really help me learn. The teacher requires detailed answers. Thank you sooooooo much, you have no idea.

Also, I am nearly leaglly blind and I am dyslexic so if you could please write clear it would help so much. I just want to learn like everyone else. SUPER SUPER THANK YOU

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6. NOTE: This question contains an intro but the questions are easier than others and thus worth less points Iodine will turn a deep reddish-brown color when added to starches,but remains lighter brown when added to simple sugars or monosaccharides. The degree of color change can be quantified by measuring the absorbance of light at 492nm using a spectrophotometer. An assay can be performed where the progress of a reaction that turns glucose into glycogen can be monitored by the increase of dark signal (measured at 492nm). You are presented with 3 unlabeled experimental samples and 5 labeled control samples. First, you incubate the unreacted control samples with iodine, measure their absorbance on the spectrophotometer, and get the following results ontrol samples iodine test response 0.3 0.15 water 5mg/ml 5mg/ml 1mg/ 1mg/ml glycogen glucose glycogen glycogen + 1mg/ml cose You then mix the three experimental unknown samples with the reaction mix (containing the necessary enzymes and cofactors to turn glucose to glycogen). You take a sample at time 0 and a sample after a 6Q minute incubation and test their reactivity to iodine. The absorbance at 492nm of those samples is below Experimental samples iodine test responses 0.25 0.2 0.15 0.05 0 sample 1 sample 2 sample 3 sample 1 sample 2 sample 3 - time 0time 0 -time 060min-60 min -60 min

Explanation / Answer

6A. Of the 5 control samples, which sample, if any is the blank?

The 5 control samples are found in the 1st graphic (water, 5mg/ml glycogen, 5 mg/ml glucose, 1mg/ml glycogen, 1mg/ml glycogen + 1 mg/ml glucose). So from all those 5 samples, the blank is WATER as is the only one with no reactive material in it but just water.

6B. What would be an appropriate negative control for the glycogen assay performed on the 3 unknown samples?

Again, we need to choose from the first graph as it contains the CONTROL samples, the negative control would be the one that produces the smallest absorbance value, but is not the blank (water). In this case, the negative control is the 5mg/ml glucose sample as it contains everything but is missing a critical component (the enzyme that polymerases the glucose to produce glycogen), therefore not deep brown color and resulting in very low absorbance.

6C. Because you used exactly the same reaction mix and reaction conditions for three experimental conditions, you can conclude that the results of the assay must be due to differences in the contents of the tubes 1-3. That was the only difference between the three conditions. You try to test this by using a technique called nuclear magnetic resonance (NMR) that tells you the molecular formulas for samples 1-3, and you are surprised to find that two of the three samples yield the exact same formula. The results are below:

Sample 1: C6H12O6

Sample 2: C6H12O6

Sample 3: C6H12

Using the results of the experiment and what you know about carbohydrate biology, how can you explain the NMR results for these samples? Be as specific about the contents of the tubes as you can.

Sample 1 for sure contains D-glucose as it was able to form glycogen after 60 minutes of reaction, while sample 2, although having the same chemical formula than D-glucose, it can be any other hexose (C6H12O6), like mannose, galactose, fructose, or even L-glucose (L-isomer of glucose), all of them incapable to be building blocks to produce glycogen. Finally, sample 3 is not even an hexose. In summary, sample 1 = D-glucose, sample 2 = any other hexose except for D-glucose, and sample 3 = not even an hexose.

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