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    I found that reducing sugars are those with ketone / aldehyde groups and was told that glucose is an example.

    Glucose has no aldehyde / ketone group (no C=O)

    whats going on
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    the only bond with oxygen is C-O
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    (Original post by jsmith6131)
    I found that reducing sugars are those with ketone / aldehyde groups and was told that glucose is an example.

    Glucose has no aldehyde / ketone group (no C=O)

    whats going on
    Its got something to do with the presence of a hemiacetal group-(http://en.wikipedia.org/wiki/Hemiacetal). Apparently its a mix of alcohol and either ketone/aldehyde
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    I cant see the group though
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    as in the ketone or aldehyde
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    if you're doing AS bio unit one, let me be the first to say, who gives a **** about what's not on the syllabus
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    it is one the sylabus - we need to know how to distuinguish between reducing and non-reducing sugars
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    (Original post by jsmith6131)
    it is one the sylabus - we need to know how to distuinguish between reducing and non-reducing sugars
    but you don't need to know what a reducing sugar is, just that all monosaccharides are reducing sugars, and some disaccharides (maltose is the only one quoted in the book, so therefore the only one you need to know). Benedicts reagent for reducing, benedicts- HCL and sodium hydrocarbonate- benedicts again, for non reducing

    edit: unless you're doing a different board- I'm doing AQA
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    a)
    could you please list the reducing and non-reducing sugars I need to know

    b)
    Could we still address the inital question as I am intersted
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    (Original post by jsmith6131)
    I found that reducing sugars are those with ketone / aldehyde groups and was told that glucose is an example.

    Glucose has no aldehyde / ketone group (no C=O)

    whats going on
    It does. There are two forms of glucose... open and closed form.

    Glucose is an aldose sugar. All monosaccharides are reducing sugars.

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    ok then, but in an exam I will only be shown a closed ring
    how am i to know if it is reducing or not
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    (Original post by jsmith6131)
    a)
    could you please list the reducing and non-reducing sugars I need to know

    b)
    Could we still address the inital question as I am intersted
    a) glucose, fructose, galactose are all reducing sugars cited in the book. you need to know that glucose and glucose is maltose, glucose and fructose is sucrose, and glucose and galactose is lactose. You don't need to know any non-reducing sugars, but you need to know how to test for them. The question may say "Monfedsfjnerdsjfd did not turn red when tested as a reducing sugars, how can you find out if it is a non-reducing sugar"
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    Stick to whats in ya text book, I won't jump the gun and say that your over-complicating things as I don't know your exam board - but if it's not in your offical text book provided by the exam board I wouldn't worry! What exam board is it? Sounds a bit ****ty, more like Chemistry than Biology.
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    (Original post by jsmith6131)
    ok then, but in an exam I will only be shown a closed ring
    how am i to know if it is reducing or not
    you don't need to know the above diagram, or anything about open or closed- all you need to know is that all monosaccharides are reducing sugars. the only monosaccharides you need to know are the ones in my above post
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    (Original post by KingofSpades)
    you don't need to know the above diagram, or anything about open or closed- all you need to know is that all monosaccharides are reducing sugars. the only monosaccharides you need to know are the ones in my above post
    This does seem more likely on the basis of my course.
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    Reducing sugars are monosaccharides that have between 3 and 7 carbon chain rings. Glucose is an example of a reducing sugar and it's a hexose sugar. Aldehyde and Ketone are functional groups and, in my history of this stuff, I've never seen anyone relate aldehyde or ketone to a reducing sugar. It's not important to know that all reducing sugars contain ketone or aldehyde, it's not a specific property of a reducing sugar.
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    thanks guys
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    we can distinguish between a reducing and non reducing sugar by tests:

    The reducing sugar: We use benedicts test by adding the sugar to benedicts (Copper sulphate) and the solution should turn RED for a reducing sugar and BLUE for a NON reducing sugar.

    Non Reducing sugar: We do the normal benedicts test and it should turn BLUE. We then add HCL to the sugar and place it in a hot bath for 5 minutes this will hydrolyse the di or polysaccharide into its monosaccharides. We then add sodium hydroxide to neutralise the solution then add benedicts and the solution should turn RED to show it is made of reducing sugars.
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    [QUOTE=NinjaRikki;29117186]we can distinguish between a reducing and non reducing sugar by tests:

    The reducing sugar: We use benedicts test by adding the sugar to benedicts (Copper sulphate) and the solution should turn RED for a reducing sugar and BLUE for a NON reducing sugar.

    Is that all? cuz in my CGP , they mentioned colour changes from blue to red
    like blue>green>yellow>orange>brick red !!!
    I dont need to whats in between , do I?! :rolleyes:
 
 
 
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