mono and disaccharides

Question 1

What elements make up a carbohydrate?

Answer 1

Carbon, hydrogen and oxygen

Question 2

What are the three groups carbohydrates are classified into?

Answer 2

Monosaccharides, disaccharides and polysaccharides

Question 3

Which two of the three groups are small and soluble?

Answer 3

Monosaccharides and disaccharides

Question 4

What are monosaccharides mainly used in?

Answer 4

Respiration

Question 5

Name three monosaccharides.

Answer 5

Glucose, fructose and galactose

Question 6

What is the formula of these monosaccharides?

Answer 6

C6H12O6

Question 7

What is it called when monosaccharides all have the formula C6H12O6?

Answer 7

Hexoses

Question 8

What is it called when a compound has the same formula but a different name?

Answer 8

Isomer

Question 9

Are monosaccharides reducing or non-reducing sugars?

Answer 9

Reducing

Question 10

What are the two isomers of glucose?

Answer 10

Alpha glucose and beta glucose

Question 11

How are disaccharides formed?

Answer 11

In a condensation reaction by a glycosidic bond

Question 12

What small molecule is released in a condensation reaction?

Answer 12

Water

Question 13

Name three disaccharides.

Answer 13

Maltose, lactose and sucrose

Question 14

What is the general word equation for a condensation reaction forming a disaccharide?

Answer 14

Monosaccharide + monosaccharide → disaccharide + water

Question 15

What is the general symbol equation for a condensation reaction forming a disaccharide?

Answer 15

C6H12O6 + C6H12O6 → C12H22O11 + H2O

Question 16

Which two monosaccharides make maltose?

Answer 16

Glucose and glucose

Question 17

Which two monosaccharides make sucrose?

Answer 17

Glucose and fructose

Question 18

Which two monosaccharides make lactose?

Answer 18

Glucose and galactose

Question 19

What is the reaction that breaks down a disaccharide?

Answer 19

Hydrolysis reaction

Question 20

How can disaccharides be hydrolysed?

Answer 20

Heating with acid or with an enzyme

Question 21

What is the test for reducing sugars?

Answer 21

Small sample mixed with Benedict’s, heated to 95°C in a water bath. A brick red precipitate is the positive result. If it is blue, no reducing sugar is present.

Question 22

What is a qualitative test?

Answer 22

A test that doesn’t allow to compare results from different samples - it is subjective

Question 23

What would a quantitative Benedict’s test produce?

Answer 23

A colour whose intensity depends on the concentration of reducing sugar in a solution

Question 24

What is a semi-quantitative useful for?

Answer 24

Comparing the concentration of reducing sugars in different samples/solutions

Question 25

What are some control variables for a semi-quantitative Benedict’s test?

Answer 25

Same volume of Benedict’s solution, same volume of the sample solutions and every sample is heated for the same time at the same temperature

Question 26

Which colour will the solution turn if there’s a high concentration of reducing sugars present?

Answer 26

Brick red

Question 27

Which colour will the solution turn if there’s a low concentration of reducing sugars present?

Answer 27

Yellow or green

Question 28

What is a problem with this method?

Answer 28

It is subjective (different people may have different views)

Question 29

What is the method for a quantitative Benedict’s test?

Answer 29

Perform Benedict’s test on reducing sugar solutions of known concentrations, use a colorimeter to measure the absorbance of each known solution, and plot a graph of known concentration (x axis) against absorbance (y axis)

Question 30

What is this graph called?

Answer 30

A calibration curve

Question 31

Why is this test quantitative?

Answer 31

It gives data and numerical results - it’s objective

Question 32

What are some control variables for this test?

Answer 32

Same volume of Benedict’s solution, same volume of the sugar solutions, and every sample is heated for the same time at the same temperature

Question 33

What is the non-reducing sugar?

Answer 33

Sucrose

Question 34

What is the test for non-reducing sugars?

Answer 34

Take a small sample and heat with Benedict’s at 95°C to confirm a negative result, hydrolyse another sample by heating at 95°C with dilute acid, when cooled, neutralise with alkali, add same concentration of Benedict’s and heat at 95°C in a water bath. A brick red colour will show sucrose was present