1.3 Carbohydrates- disaccharides and polysaccharides Flashcards

1
Q

what is a disaccharide?

A

pair of monosacchaides

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2
Q

what are examples of monosaccharides that make up disaccharides?

A
glucose+glucose= maltose
glucose+frunctose= sucrose
glucose+galactose= lactose
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3
Q

how are disaccharides formed?

A

condensation reaction

  • molecule of water is removed
  • glycosidic bond
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4
Q

what bonds are in disaccharides?

A

glycosidic bond

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5
Q

how are disaccharides breoken down?

A

hydrolysis

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6
Q

what is the process of hydrolysis?

A

water is added

breaks glycosidic bond

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7
Q

what is the test for non reducing sugars?

A
  • 2cm^3 food sample in liquid form + 2cm^3 benedicts reagent in test tube
  • put in gently boiling water bath for 5 mins
    • solutin remains blue= no reducing sugar
  • 2cm^3 food sample+2cm^3 hydrochloric acid in test tube
  • put in gently boiling water bath for 5 mins
    • sodium hydrocarbonate solution
    • 2cm^3 benedicts reagent in test tube
  • put in gently boiling water bath for 5 mins
    • turns orange/brown= non reducing sugar present
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8
Q

why is dilute hydrochloric acid added in the test for non reducing sugars?

A

to hydrolyse any disaccharides into its constituent monosaccharides

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9
Q

why is sodium hydrocarbonate solution added in the test for non reducing sugars?

A

to neutralise hydrochloric acid

benedics reagent doesnt work in acidic conditions

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10
Q

how will you get a positive result from the benedicts reagent in the test for non reducing sugars?

A

reducing sugars (mnonosaccharides) produced from the hydrolysis of the non reducing sugar

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11
Q

what are polysaccharides ?

A

polymers- formed by combining many monosaccharides

-condensation reactions- glycosidic bonds

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12
Q

how are polysaccharides formed?

A

condensation reaction

  • molecule of water is removed
  • glycosidic bond
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13
Q

what bonds are in polysaccharides?

A

-glycosidic bond

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14
Q

what is produced when polysaccharides are hydrolysed?

A

disaccharides/monosaccharides

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15
Q

what size are polysaccharide molecules?

A

large

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16
Q

what is the test for starch?

A
  • place 2cm^3 sample into test tube
  • add 2 drops of iodine
  • shake/stir
    • blue/black colouration= starch present