Biological Molecules - Sugars

Question 1

What elements do all carbohydrates contain

Answer 1

Carbon, hydrogen, oxygen

Question 2

What are the monomers that carbohydrates made from called

Answer 2

monosaccharides

Question 3

Give some examples of monosaccharides

Answer 3

Glucose, fructose, galactose

Question 4

Describe the structure of glucose

Answer 4

It is a hexose sugar, which is just a monosaccharide with 6 carbon atoms in each molecule

Question 5

What are the different types of glucose

Answer 5

a-glucose and B-glucose, these are isomers of glucose

Question 6

What is an isomer

Answer 6

molecules with the same molecular formula but with the toms connected in a different way

Question 7

How is a disaccharide formed

Answer 7

Formed when 2 monosaccharides join together by a condensation reaction realising a molecule of water and a glycosidic bond is formed between the 2 monosaccharides

Question 8

How is sucrose formed

Answer 8

Formed from a condensation reaction between glucose and a fructose molecule

Question 9

How is lactose formed

Answer 9

Formed from a condensation reaction between glucose and galactose molecule

Question 10

How is maltose formed

Answer 10

Formed from a condensation reaction between 2 glucose molecules

Question 11

What are the 2 groups that sugars are classified in

Answer 11

Reducing sugar or non reducing sugar

Question 12

What test do you use for sugars

Answer 12

Benedicts Test

Question 13

What do reducing sugars include

Answer 13

They include all monosaccharides and some disaccharides

Question 14

Explain how a Benedict’s test works for reducing sugars

Answer 14

Add Benedict’s reagent (blue) to a sample and heat it in a water bath.

Question 15

What is the colour change if a reducing sugar is present

Answer 15

A coloured precipitate will form, colours from green, yellow, orange and brick red precipitate would from. If a reducing sugar was not present the sample would stay blue.

Question 16

How does the concentration of the reducing sugar affect the colour change

Answer 16

The higher the concentration of reducing sugar the further the colour change goes

Question 17

What is a more accurate way of comparing the amount of reducing sugars in a solution

Answer 17

You can filter the solution and weigh the precipitate or you could remove the precipitate and use a colorimeter to measure the absorbance of the remaining Benedicts reagent

Question 18

What could still be present if the results for the reducing sugars test was negative

Answer 18

Non-reducing sugar

Question 19

How do you test for a non-reducing sugar

Answer 19

First break the sample down into its monosaccharides, you do this by getting a new sample of the test solution and add dilute hydrochloric acid and carefully heat it in a water bath. You then neutralise it by adding sodium hydrogen carbonate. And lastly carry out a normal Benedict’s test.