Carbohydrates Worksheet

Natalie Pemberton-Parris 00027917

2nd October 2014CHEM 121 Carbohydrates WorksheetSECTION A (26 marks)

1. Which elements do simple carbohydrates contain, and in what ratio?

(1 mark)Carbon, hydrogen and oxygen. 1:2:12. If a monosaccharide has 11 oxygen atoms, how many hydrogen atoms does it contain? (1 mark)

There will be 22 hydrogen atoms3. Based on their molecular formulas, which of the following are NOT simple carbohydrates? (1 mark)a) C3H803b) C10H18O9c) C18H32O16d) C4H8O2e) C16H32O2f) C6H12O64. For each molecule below, determine if it is a monosaccharide, a disaccharide, or a polysaccharide:

(9 marks)a) Fructose

Monosaccharide.b) Ribose

Monosaccharide.c) Cellulose

Polysaccharide.d) Glucose

Monosaccharidee) Sucrose

Disaccharidef) Glycogen

Polysaccharideg) Chitin

Polysaccharideh) Starch

Polysaccharidei) Maltose

Disaccharide5. Complete these word equations.

a) (-D-Glucose + (-D-glucose ( Maltose+ water

(1 mark)b) (-D-Glucose + (-D-fructose ( Sucrose + water

(1 mark)c) Monosaccharide + monosaccharide ( Disaccharide + water

(1 mark)

d) Lactose + water ( (-D-Glucose + (-D-Galactose

(1 mark)e) Disaccharide + water ( Monosaccharide + Monosaccharide

(1 mark)6. Explain what a dehydration synthesis (condensation) reaction is.

(1 mark)A dehydration synthesis reaction is the combination of elements and/or simple compounds to form a complex compound by removing the H2O. Dehydration synthesis occurs in the combination of many things, such as two monosaccharides that come together to form a disaccharide.

7. Explain what a hydrolysis reaction is.

(1 mark)Hydrolysis is the reverse of dehydration synthesis. During hydrolysis, bonds between complex molecules are broken with the addition of a water molecule. Sucrose + H2O ----> Glucose + Fructose

8. Starch is composed of two types of polymers named amylose and amylopectin.(2 marks)9. Give the full name of the linkage(s) present in amylose.

(1 mark)Alpha 1, 4 O Glycosidic linkage

10. Give the full name of the linkage(s) present in amylopectin.

(2 marks)Alpha 1, 4 O Glycosidic linkage

Alpha 1, 6 O Glycosidic Linkage

11. Would starch be considered a reducing sugar?

(1 mark)Starch would not be considered a non-reducing because it does not have free aldehyde or ketone groups that react with the blue cuprous ions in the Benedict solution. Starch is also a polysaccharide, and polysaccharides tend to be non-reducing.

12. Explain your answer for question 11.

(1 mark)The functional group of carbohydrate is carbonyl group which can be divide into ketone and aldehyde. Both ketone and aldehyde can reduce other substances. Benedict solution contain Cu2+. When benedict solution reacts with reducing agents, it will be reduced to Cu+ where we can observe the colour of the solution change from blue to brick red. Glucose, Fructose, Galactose and other Monosaccharides are reducing sugar because the functional group are available to reduce the Cu2+ in benedict solution. However, in sucrose (form from one glucose and one fructose) both the functional group are involve in making bond. Therefore no functional group available to reduce the Cu2+. In starch the same process applies as theres no free functional group.

SECTION B (14 marks)

13. Figure 1 shows two molecules labeled a. and b.

Figure 1a) Which is a ketose sugar? B

(1 mark)b) Circle and name the functional group on the ketose sugar.

(2 marks)c) Which is an aldose sugar? A

(1 mark)d) Circle and name the functional group on the aldose sugar.

(2 marks)e) Draw enantiomers of the two molecules above.

(2 marks)Enantiomer AEnantiomer B

14. Draw the Haworth structures of the following carbohydrates:

(-D RIBOSE(-D GLUCOSE

15. (a) Draw the Fischer projections for both D and L forms of mannose

Mannose D FormMannose L Form

(b) Draw the Haworth projections for (-D mannose and (-D mannose.

(-D mannose(-D mannose