Sugars Flashcards

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1
Q

What elements do all carbohydrates contain?

A

Carbon.
Hydrogen.
Oxygen.

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2
Q

What monomers make up carbohydrates?

A

Monosaccharides.

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3
Q

Examples of monosaccharides?

A

Glucose.
Fructose.
Galactose.

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4
Q

What kind of sugar is glucose?

A

A hexose sugar - a monosaccharide with six carbon atoms in each molecule.

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5
Q

What are the types of glucose?

A

Alpha glucose.

Beta glucose.

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6
Q

How are alpha and beta glucose related?

A

Isomers.

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7
Q

What is an isomer?

A

Molecules with the same molecular formula as each other, but with the atoms connected in a different way.

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8
Q

How is a disaccharide formed?

A

Two monosaccharides join together by condensation reactions.

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9
Q

What bond forms between two monosaccharides?

A

Glycosidic bond.

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10
Q

What disaccharide is formed when glucose and fructose join?

A

Sucrose.

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11
Q

What disaccharide is formed when glucose and galactose join?

A

Lactose.

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12
Q

What can sugars be classified as?

A

Reducing sugars.

Non-reducing sugars.

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13
Q

What is the test for sugars?

A

The Benedict’s Test.

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14
Q

What colour is Benedict’s reagent?

A

Blue.

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15
Q

How do you test for a reducing sugar?

A

Add Benedict’s reagent.
Heat it in a water bath that has been brought to the boil.
If the test is positive a coloured precipitate will form.

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16
Q

How do you know how high the concentration of a reducing sugar is?

A

The higher the concentration the further the colour change will go.
Green to Yellow to Orange to Brick Red.

17
Q

What is a more accurate way of comparing concentrations of reducing sugars?

A

Filter the solution and weigh the precipitate.

OR

Remove the precipitate and use a colorimeter to measure the absorbance of the remaining Benedict’s reagent.

18
Q

What can still be present if a reducing sugars test is negative?

A

Non-reducing sugar.

19
Q

What must be done to test a non-reducing sugar?

A

Must be broken down into monosaccharides.

20
Q

How do you break non-reducing sugars down into monosaccharides? And then test them?

A

Get a new sample of the test solution.
Add dilute hydrochloric acid.
Carefully heat it in a water bath that has been brought to the boil.
Neutralise it by adding sodium hydrogen carbonate.
Carry out the Benedict’s test as you would for a reducing sugar.