Dr. Bhavsar, Congratulations on the very explanatory video! Could you explain the reason that can lead to a negative glucose standard curve (spectrophotometer reading)?
Hello sir. Could by chance have a summary of the important points that should be mentioned in the exam regarding this practical? As the video is explaining the process but i can’t understand what should we actually write in an exam? Would it be the whole process including the steps and the observations? And also sir. Regarding my exam board they’re asking for a “semi-quantitative test” will that be with the curve?
quantitative is using the calibration curve. semi-quantitative is comparing the colours to say which is 'more' or 'less' concentrated with reducing sugar.
Hi, can you please tell me if the calibration curve will always go down with quantitative testing? I used Solutions 0.1%, 0.5%,1.0%,1.5% and 2.0% (all 5ml) with a control of water and Benedict's reagent(also 5ml) 0.0% my curve goes up...Thank you!
***** Good question. It all depends what you are measuring. If you are removing the precipitate, then the blue colour (of copper ions) should decrease with increasing glucose concentration. In that case absorbance of red light should decrease (and transmission increases, if that's what you're measuring). BUT, if you're leaving the precipitate (red, CuO) in the tubes, and looking at absorbance of blue light, in that case, your absorbance will increase as glucose concentration increases (and transmission will therefore go down). If this doesn't resolve your question, maybe you could give me details of your experiment and the colour of the solutions you are testing. thanks!
+LSC biology so if we dont use the colorimeter and the calibration curve, does the test called semi-quantitative test? and also, i thought dilution is involved in this one, where we add distilled water
+Najiah HMG without the calibration curve, it is not quantitative because we don't know what concentration of reducing sugar the colour corresponds to. Put simply: comparing colours by eye is qualitative. Comparing colours by colorimeter is semi-quantitative. Comparing colours with colorimeter AND using a calibration of known concentrations (so we know what concentration each colour represents) is quantitative. Water would be used only if the solutions are too intense for the colorimeter. In that the volume added should be kept the same.
I have a question about Benedict tests. there are lots of videos relating to the Benedict test of glucose, but I have never seen what happens when you try to use the benedict test on Sucrose. Can you tell me what happens?
+tony Tran yes. Sucrose is a disaccharide and it is not a reducing sugar. The chemical group needed to react with Benedicts reagent is not available in sucrose. So sucrose does not cause the appearance of red precipitate when heated with Benedicts reagent.
It is a non-reducing sugar so you would convert it into a reducing sugar. This can be done by adding hydrochloric acid, heating in the water bath, then adding sodium hydrogencarbonate (neutralises acidity), then proceeding with the normal Benedict's test.
Hi, could you tell me?, if i test for quantitative of molass(type of sugar) or any sugar. Can i use pure reducing sugar for making standard curve? Thank you ^^
This video was super helpful!! But I would really like to know what setting the colorimeter was set to to be able to get an accurate reading. Please let me know as I am replicating this method! Thanks :)
+That Chickpea Chick / Summer Lo set to reading absorbance, with blue/green filter (you may need to check which wavelengths that corresponds to). Good luck.
i have question for the last part, about calibration curve: can we use any machine to detect exactly the curve? like spectrometer or something like that? thanks
Yes spectrophotometer would work as long as you are detecting the right wavelength. Colorimeters are cheaper and will also work but you must make sure to use the right filter.
oanh dao thi Honestly, I haven't tested this method at low levels and so I couldn't say. The Method would work, but it would depend on how sensitive the colorimeter is. I would test the method with standard concentrations of glucose that span the range you are interested in. Good luck!
I combined 1 ml of a 1% Glucose Standard Solution and 4 ml of benedict's quantitative solution. After combining the two things in a test tube, I put the test tube in beaker full of hot water (80 degrees celcius). After 5 minutes, I noticed that the solution had changed from the blue green color to a light blue color. At the bottom of the test-tube, there was a white powder. Image of White Powder i.imgur.com/TSzMiFD.jpg?1
+Jaeho Lee I wish I could say something more helpful than, that is really quite inexplicable. We usually have the glucose solution and Benedict's in a 1:1 ratio, and usually have glucose solution in excess over Benedict's rather than the other way round. We also use a waterbath that maintains the 80C temperature and even then sometimes it can take up to 15 minutes. Without a waterbath it's likely your temp dropped and possibly the reaction didn't go to completion. I have a theory also, that perhaps if your glucose solution was more than 1% (significantly more), adding the benedicts may have caused the glucose to precipitate out of the solution and so not take part in the reaction AND explaining the white crystals. But that's a bit out there!
I redid the experiment with a 1:1 ratio. I also used a water bath that maintained an 80 C for 15 minutes. After I did the experiment, the solution turned yellow, but the precipitate was white instead of red.
+Jaeho Lee It seems to me that you used the quantitative Benedict's reagent, and +LSC Biology used the qualitative Benedict's reagent. LSC Biology's method gives an estimation of glucose concentration, while your quantitative solution is used to accurately determine the glucose concentration (either by I2/thiosulphate redox titration or by colourimetric measurements (absorbance)). Both solutions give different precipitates. Check this link for the difference in composition between the two: www.mystrica.com/Applications/Benedicts
+ROMAN HANG LIMBU blue solutions absorb most strongly in red part of visible light spectrum. So for colorimetric analysis of blue solutions, light is passed through a red filter to get more accurate readings of transmission/absorbance.
+ROMAN HANG LIMBU yes. It's something that visible light can go through, some wavelengths are absorbed and others can pass through. A red filter allows red light to pass through, not others.
en.m.wikipedia.org/wiki/Reducing_sugar If a sugar molecule has an aldehyde or ketone group (ie a c=o somewhere) it can act as a reducing agent. So all monosaccharides can be reducing when they are in straight chain form. But when monosaccharides are joined by glycosidic bonds, they can’t go into the straight chain form, and so don’t have the c=o group, so are not reducing.
If you have any questions about this please use this space and I will respond as soon as I can!
Dr Bhavsar can you please arrange all the sugars in order of their reactivity...
Do you happen to know the expected color change for coconut water? I mean, what shade should I expect when I perform the experiment?
I don’t know that. But you could look up the expected composition and see if it contains any reducing sugars.
Dr Bhavsar Ah, okay. Thank you! Both for the response, and the rate at which you replied. :)
Dr Bhavsar what should u do if the experiment is semi quantitative?
Great video with very clear explanations. Hope this comes in my AS Biology exam in summer.Thank you!
The pacing of the video is great, so it was very helpful
Dr. Bhavsar, Congratulations on the very explanatory video! Could you explain the reason that can lead to a negative glucose standard curve (spectrophotometer reading)?
Online lessons are gonna be a breeeeeeeeze with these videos!!
Having a tons of them is sometimes confusing tho😅
I'm learning a lot here, please can you show something like food. thank you
This video helped me to understand my lab.
may the science Gods Bless ur soul...lol Thanks a million
please increase your voice
6:20
Hello sir.
Could by chance have a summary of the important points that should be mentioned in the exam regarding this practical?
As the video is explaining the process but i can’t understand what should we actually write in an exam? Would it be the whole process including the steps and the observations?
And also sir. Regarding my exam board they’re asking for a “semi-quantitative test” will that be with the curve?
quantitative is using the calibration curve. semi-quantitative is comparing the colours to say which is 'more' or 'less' concentrated with reducing sugar.
thank you so much
Thank you! This is so helpful! :)
Anyone retaking the biology Empa?
Thankyou this was so helpful :)
+Amy Whitaker you're welcome.
thank you so much ! This video was really helpful !
You're very welcome.
Hi, can you please tell me if the calibration curve will always go down with quantitative testing? I used Solutions 0.1%, 0.5%,1.0%,1.5% and 2.0% (all 5ml) with a control of water and Benedict's reagent(also 5ml) 0.0% my curve goes up...Thank you!
***** Good question. It all depends what you are measuring. If you are removing the precipitate, then the blue colour (of copper ions) should decrease with increasing glucose concentration. In that case absorbance of red light should decrease (and transmission increases, if that's what you're measuring). BUT, if you're leaving the precipitate (red, CuO) in the tubes, and looking at absorbance of blue light, in that case, your absorbance will increase as glucose concentration increases (and transmission will therefore go down). If this doesn't resolve your question, maybe you could give me details of your experiment and the colour of the solutions you are testing. thanks!
I
I like this practical
It's amazing mashAllah
thank you!
What wavelengths did you set for blue and red light? Thanks!!
+LSC biology
so if we dont use the colorimeter and the calibration curve, does the test called semi-quantitative test? and also, i thought dilution is involved in this one, where we add distilled water
pleasee reply asap
+Najiah HMG without the calibration curve, it is not quantitative because we don't know what concentration of reducing sugar the colour corresponds to. Put simply: comparing colours by eye is qualitative. Comparing colours by colorimeter is semi-quantitative. Comparing colours with colorimeter AND using a calibration of known concentrations (so we know what concentration each colour represents) is quantitative. Water would be used only if the solutions are too intense for the colorimeter. In that the volume added should be kept the same.
thanks for this vedio....
Does a non-carbohydrate substance be positive in Benedict’s test?
i think it can, since all it's really testing for is a free aldehyde or ketone group.
I have a question about Benedict tests.
there are lots of videos relating to the Benedict test of glucose, but I have never seen what happens when you try to use the benedict test on Sucrose. Can you tell me what happens?
+tony Tran yes. Sucrose is a disaccharide and it is not a reducing sugar. The chemical group needed to react with Benedicts reagent is not available in sucrose. So sucrose does not cause the appearance of red precipitate when heated with Benedicts reagent.
+LSC Biology so it would not have any color difference?
Thank you
+tony Tran sucrose is not a reducing sugar, so no, it would not make a colour change.
It is a non-reducing sugar so you would convert it into a reducing sugar. This can be done by adding hydrochloric acid, heating in the water bath, then adding sodium hydrogencarbonate (neutralises acidity), then proceeding with the normal Benedict's test.
Great!
Yeah this was really helpful
Glad it helped
Hi, could you tell me?, if i test for quantitative of molass(type of sugar) or any sugar. Can i use pure reducing sugar for making standard curve? Thank you ^^
Chaiyasit Phawa yes. Jus make a serial dilution.
This video was super helpful!! But I would really like to know what setting the colorimeter was set to to be able to get an accurate reading. Please let me know as I am replicating this method! Thanks :)
+That Chickpea Chick / Summer Lo set to reading absorbance, with blue/green filter (you may need to check which wavelengths that corresponds to). Good luck.
Bando Mo in the blocc
Sir, is there any reference for this experiment?
The reference should be solutions of reducing sugar with known concentration.
very helpful, thank you!
i have question for the last part, about calibration curve: can we use any machine to detect exactly the curve? like spectrometer or something like that? thanks
Yes spectrophotometer would work as long as you are detecting the right wavelength. Colorimeters are cheaper and will also work but you must make sure to use the right filter.
+LSC Biology Can we use this method to measure quiet low glucose concentration like mmol/l?
oanh dao thi Honestly, I haven't tested this method at low levels and so I couldn't say. The Method would work, but it would depend on how sensitive the colorimeter is. I would test the method with standard concentrations of glucose that span the range you are interested in. Good luck!
thanks alot :)
Dr Bhavsar Biology has Testing for Reducing SugarsTesting for Reducing SugarsTesting for Reducing SugarsTesting for Reducing Sugars
I got a white powder instead of the red precipitate. What went wrong?
That's quite unexpected. Tell me the details of your experiment.
I combined 1 ml of a 1% Glucose Standard Solution and 4 ml of benedict's quantitative solution. After combining the two things in a test tube, I put the test tube in beaker full of hot water (80 degrees celcius). After 5 minutes, I noticed that the solution had changed from the blue green color to a light blue color. At the bottom of the test-tube, there was a white powder.
Image of White Powder
i.imgur.com/TSzMiFD.jpg?1
+Jaeho Lee I wish I could say something more helpful than, that is really quite inexplicable. We usually have the glucose solution and Benedict's in a 1:1 ratio, and usually have glucose solution in excess over Benedict's rather than the other way round. We also use a waterbath that maintains the 80C temperature and even then sometimes it can take up to 15 minutes. Without a waterbath it's likely your temp dropped and possibly the reaction didn't go to completion. I have a theory also, that perhaps if your glucose solution was more than 1% (significantly more), adding the benedicts may have caused the glucose to precipitate out of the solution and so not take part in the reaction AND explaining the white crystals. But that's a bit out there!
I redid the experiment with a 1:1 ratio. I also used a water bath that maintained an 80 C for 15 minutes. After I did the experiment, the solution turned yellow, but the precipitate was white instead of red.
+Jaeho Lee It seems to me that you used the quantitative Benedict's reagent, and +LSC Biology used the qualitative Benedict's reagent. LSC Biology's method gives an estimation of glucose concentration, while your quantitative solution is used to accurately determine the glucose concentration (either by I2/thiosulphate redox titration or by colourimetric measurements (absorbance)). Both solutions give different precipitates. Check this link for the difference in composition between the two: www.mystrica.com/Applications/Benedicts
ik this sounds dumb but wat is glucose
+Trillian Times you need to watch my video on carbohydrates!
Trillian Times sugar
What did you mean by Red filter? please help...
+ROMAN HANG LIMBU blue solutions absorb most strongly in red part of visible light spectrum. So for colorimetric analysis of blue solutions, light is passed through a red filter to get more accurate readings of transmission/absorbance.
Dr Bhavsar But what exactly is a Red filter? Is it something on the actual colorimeter? Thanks for the response.
+ROMAN HANG LIMBU yes. It's something that visible light can go through, some wavelengths are absorbed and others can pass through. A red filter allows red light to pass through, not others.
Thankyou very much.
N
this video is so slow yet so chaotic
Is ribulose a reducing sugar?
en.m.wikipedia.org/wiki/Reducing_sugar
If a sugar molecule has an aldehyde or ketone group (ie a c=o somewhere) it can act as a reducing agent. So all monosaccharides can be reducing when they are in straight chain form. But when monosaccharides are joined by glycosidic bonds, they can’t go into the straight chain form, and so don’t have the c=o group, so are not reducing.
@@LSCBiology Thank you
I was waiting for Dr Strange to show up
sorry to disappoint!
good fast it
#
i dont care
LOL
not useful
ouch. why?