Danii7
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I've been set two questions for biology and I was wondering if anyone could help me please?

1. Outline a method for a fully quantitative test for reducing sugars.

2. Suggest how you could distinguish a sample of glucose from a sample of maltose using Benedict's reagent.
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Kvothe the Arcane
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(Original post by Danii7)
I've been set two questions for biology and I was wondering if anyone could help me please?

1. Outline a method for a fully quantitative test for reducing sugars.

2. Suggest how you could distinguish a sample of glucose from a sample of maltose using Benedict's reagent.
Hi there. What exactly are you struggling with?
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Rob_mcm
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1. This is just simply learning the method for the test for reducing sugars, first add Benedict's reagent to your sugar sample, heat in a water bath for a few minutes and if a orange/red precipitate forms then the sugar is reducing.

2. This one seems unusual as this test does not determine how much reducing sugar there is, or which reducing sugar is present, the only thing I can think of is that since maltose is a disaccharide made up of 2 glucose monosaccharides, when you do the test for reducing sugars you would get a darker colour due to more being present.
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Danii7
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(Original post by Rob_mcm)
1. This is just simply learning the method for the test for reducing sugars, first add Benedict's reagent to your sugar sample, heat in a water bath for a few minutes and if a orange/red precipitate forms then the sugar is reducing.

2. This one seems unusual as this test does not determine how much reducing sugar there is, or which reducing sugar is present, the only thing I can think of is that since maltose is a disaccharide made up of 2 glucose monosaccharides, when you do the test for reducing sugars you would get a darker colour due to more being present.
Thankyou!
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Danii7
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(Original post by Kvothe the arcane)
Hi there. What exactly are you struggling with?
hi, I'm struggling to answer these questions I was given as I don't know the answers to them
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typicalvirgo
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(Original post by Danii7)
Thankyou!
1. Outline a method for a fully quantitative test for reducing sugars.

So, quantitive means using NUMERICAL data, and for this we can use a colorimeter. Perform the reducing sugar test with Benedict's solution on different concentrations of glucose (0.1M, 0.2M, 0.3M etc) Don't forget to have equal volumes of solution and heat them at the same temperature for the same amount of time. Then, take samples from each one and place them in a colorimeter bottle. You should get a value for each one depending on how much light is absorbed/ radiated.
If you were measuring absorption, as the concentration increases, the number should increase since there is more precipitate causing more absorption of the light. If you were measuring radiation, the number would go down since less light is able to pass through the sample!

2. Suggest how you could distinguish a sample of glucose from a sample of maltose using Benedict's reagent.
Maltose is a disaccharide and glucose is a monosaccharide. Usually, you're taught that Benedict's solution only works on monosaccharides but maltose is an exception. So what you'd do is perform the test on both, and then look at the amount of precipitate you'd get. Maltose would give you more and glucose would give you less.

Hope this helped
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Danii7
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(Original post by typicalvirgo)
1. Outline a method for a fully quantitative test for reducing sugars.

So, quantitive means using NUMERICAL data, and for this we can use a colorimeter. Perform the reducing sugar test with Benedict's solution on different concentrations of glucose (0.1M, 0.2M, 0.3M etc) Don't forget to have equal volumes of solution and heat them at the same temperature for the same amount of time. Then, take samples from each one and place them in a colorimeter bottle. You should get a value for each one depending on how much light is absorbed/ radiated.
If you were measuring absorption, as the concentration increases, the number should increase since there is more precipitate causing more absorption of the light. If you were measuring radiation, the number would go down since less light is able to pass through the sample!

2. Suggest how you could distinguish a sample of glucose from a sample of maltose using Benedict's reagent.
Maltose is a disaccharide and glucose is a monosaccharide. Usually, you're taught that Benedict's solution only works on monosaccharides but maltose is an exception. So what you'd do is perform the test on both, and then look at the amount of precipitate you'd get. Maltose would give you more and glucose would give you less.

Hope this helped
Thankyou!! This helped so much
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LoloL2001
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Maltose is made up of 2 glucose bonded together however this means that there is only one aldehyde group per two glucose where as glucose solution has one aldehyde group per glucose so maltose will produce half the amount of reduced copper as glucose if the same masses of each is used
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Blue_Cow
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(Original post by LoloL2001)
Maltose is made up of 2 glucose bonded together however this means that there is only one aldehyde group per two glucose where as glucose solution has one aldehyde group per glucose so maltose will produce half the amount of reduced copper as glucose if the same masses of each is used
1) This thread is from 2016

2) You don't need to go into Aldehyde groups in AS Biology.
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LoloL2001
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(Original post by Blue_Cow)
1) This thread is from 2016

2) You don't need to go into Aldehyde groups in AS Biology.
People I know are using this thread and you do now
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Blue_Cow
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(Original post by LoloL2001)
People I know are using this thread and you do now
At least not for AQA Biology. I sat the new A-Level this year.
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DrawTheLine
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(Original post by LoloL2001)
People I know are using this thread and you do now
And not for OCR either as I did the new spec this year (2017 papers)
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Hannah5111
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Do you know what improvements to the method you could do for the qualitative test? What changes would you mak to obtain semi quantitative results?
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chibibotto
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Hannah5111 I am stuck on these questions too. Our teacher has given us these questions without teaching us about the topic of sugars beforehand so any help would be appreciated!
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Emelia2402
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