3.1.2 Carbohydrates

Question 1

Monosaccharide definition

Answer 1

Monomers from which larger carbohydrates are made

Question 2

Examples of monosaccharides

Answer 2

glucose
galactose
fructose

Question 3

Examples of disaccharides

Answer 3

maltose
sucrose
lactose

Question 4

Maltose

Answer 4

glucose + glucose

Question 5

Sucrose

Answer 5

glucose + fructose

Question 6

Lactose

Answer 6

glucose + galactose

Question 7

Carbohydrate

Bonds

Answer 7

Glycosidic bond

-condensation reaction between the hydroxyl groups (elimination of a water molecule)

Question 8

Give the position of the H in alpha glucose

Answer 8

H

OH

Question 9

Give the position of the H in beta glucose

Answer 9

OH

H

Question 10

Polysaccharide Definition

Answer 10

A polymer composed of many saccharide units

Question 11

Polysaccharide Examples

Answer 11

glycogen
starch
cellulose

Question 12

Glycogen

Location

Answer 12

Animals

(e.g. muscle, liver) and fungi

Question 13

Glycogen

Structure

Answer 13

Alpha glucose

Contains CHO
Branched
Glycosidic bonds (1,4 and 1,6)
└condensation reaction

Question 14

Glycogen

Structure to function

Answer 14

Energy store (glucose) in animals

Insoluble
=water potential not affected= water doesn’t diffuse into/out of cells by osmosis

Large
=doesn’t diffuse out of cells

Branched
=many ends for enzymes to act on= quickly hydrolysed to alpha glucose for respiration

Question 15

Starch

Location

Answer 15

plants

Question 16

Starch

Structure

Answer 16

Alpha glucose

Amylose
Unbranched, helical
Glycosidic bonds (1,4)
└condensation reaction

Amylopectin
Branched
Glycosidic bonds (1,4 and 1,6)
└condensation reaction

Question 17

Starch

Structure to function

Answer 17

Energy store (glucose) in plants

Insoluble
=water potential not affected= water doesn’t diffuse into/out of cells by osmosis

Large
=doesn’t diffuse out of cells

Branched
=many ends for enzymes to act on= quickly hydrolysed to alpha glucose for respiration

Helical
=compact= can store many molecules in a small space

Question 18

Cellulose

Location

Answer 18

Plants

Cell walls

Question 19

Cellulose

Structure

Answer 19

Beta glucose

Unbranched
Glycosidic bonds (1,4)
└condensation reaction

Molecules rotate 180 degrees relative to its neighbour
Adjacent chains linked by hydrogen bonds to form microfibrils

Question 20

Cellulose

Structure to function

Answer 20

Strengthens cell walls/ prevents them from bursting

Unbranched
Straight chain linked by H bonds → myofibrils
= increase strength

Question 21

Reducing sugars

Answer 21

-a sugar that can donate an electron to a substance to reduce it

-e.g. all monosaccharides (glucose), some disaccharides (maltose, lactose)
└NOT sucrose

Question 22

Benedicts test for reducing sugars

Answer 22

Add benedicts reagent in excess and heat

+) brick red precipitate (green →yellow →orange

Question 23

Comparing the amount of reducing sugars in different concentrations

Answer 23

Observe colour change (less accurate)
-darker= more concentrated

Use a colorimeter (more accurate)

• filter solution and weigh precipitate
• use colorimeter to measure absorbance of remaining benedict’s reagent

Question 24

Benedicts test for non- reducing sugars

Answer 24

-add benedicts reagent in excess and heat
(-) blue

-heat new sample with dilute HCL acid/ hydrolytic enzyme (to hydrolyse)
-add sodium carbonate (to neutralise)
-add benedicts reagent in excess and heat
(+) brick red precipitate (green →yellow →orange)

Question 25

Iodine test for starch

Answer 25

-add iodine solution to sample

(+) blue/black