Carbohydrates - monosaccharides, disaccharides + polysaccharides

Question 1

Name the four main groups of biological molecules

Answer 1

Proteins
Carbohydrates
Lipids
Nucleic acids

Question 2

Simply describe the structure of glucose

Answer 2

A hexose sugar which means it contains 6 carbon atoms

Question 3

Name the two types of glucose and their differences (in structure - draw them)

Answer 3

Alpha-glucose: hydroxyl group on the right below

Beta-glucose: hydroxyl group on the right above

Question 4

Name three monosaccharides

Answer 4

Glucose
Galactose (don't need to know diagram)
Fructose (don't need to know diagram)

Question 5

Name three disaccharides and which 2 monosaccharides they are formed by

Answer 5

Maltose - 2 alpha-glucose
Sucrose - glucose + fructose
Lactose - glucose + galactose

Question 6

Name the reaction that maltose, sucrose and lactose formed from

Answer 6

Condensation reaction

Question 7

Describe what happens in a condensation reaction

Answer 7

A disaccharide is formed from bonding two monosaccharides + a water molecule is released. A glycosidic bond is formed

Question 8

Name three polysaccharides and what they are formed from

Answer 8

Cellulose - formed by chains of beta-glucose
Glycogen - formed by many alpha-glucose molecules
Starch - formed by many alpha glucose (but differently)

Question 9

Give an example of isomers

Answer 9

Alpha and beta- glucose are different isomers of glucose

Question 10

Give the general formula of glucose

Answer 10

(CH2O)n

Question 11

Name 3-7 carbon sugars

Answer 11

No. of carbons 3-7:
3 - triose
4 - tetrose
5 - pentose
6 - hexose
7 - heptose

Question 12

Give two examples of pentose sugars

Answer 12

Ribose

Deoxyribose

Question 13

Give three examples of hexose sugars

Answer 13

Glucose
Fructose
Galactose

Question 14

Describe what happens in a hydrolysis reaction

Answer 14

Water is added to a disaccharide and the glycosidic bond is broken to form 2 monosaccharides

Question 15

Describe the test for sugars and the result if sugars are present

Answer 15

Benedict’s test:

• Add an excess of Benedict’s reagent (blue liquid) to sample
• Heat an excess in a water bath that has been boiled
• If test is positive i.e. there are sugars present, then a coloured precipitate will form

Question 16

Describe the colour of precipitate and link it to the concentration of sugars in a solution

Answer 16

blue - none
green - trace
yellow - low
orange - moderate
red - high