monosaccharides and disaccharides

Question 1

what are monosaccharides?

Answer 1

are the monomers from which larger carbohydrates are made

Question 2

what are examples of common monosaccharides?

Answer 2

glucose, galactose and fructose

Question 3

how do monosaccharides join together?

Answer 3

by a condensation reaction

Question 4

which two forms can monosaccharides occur as?

Answer 4

alpha-glucose and beta-glucose

Question 5

what is the bond that the reaction would produce a disaccharide called maltose?

Answer 5

an alpha 1-4 glycosidic bond

Question 6

how is maltose created?

Answer 6

when amylase breaks down starch

Question 7

which two monosaccharides form maltose?

Answer 7

glucose + glucose

Question 8

what is a disaccharide?

Answer 8

the sugar formed when two monosaccharides are joined by glycosidic linkage

Question 9

what are examples of other disaccharides other than maltose?

Answer 9

sucrose and lactose

Question 10

which two monosaccharides form sucrose?

Answer 10

glucose+fructose

Question 11

which two monosaccharides form lactose?

Answer 11

glucose+galactose

Question 12

how is sucrose formed?

Answer 12

by the condensation of a glucose molecule and a fructose molecule

Question 13

how is lactose formed?

Answer 13

by the condensation of a glucose molecule and a galactose molecule

Question 14

what is a polysaccharide?

Answer 14

a very large polymer comprising many monosaccharides, as with disaccharides they are joined by glycosidic bonds

Question 15

how is a polysaccharide formed?

Answer 15

by the condensation of many glucose monosaccharides

Question 16

what are the features and characteristics of polysaccharides?

Answer 16

-they are insoluble in water
-they are not sweet
-they do NOT form crystals

Question 17

what do polysaccharides take the form of?

Answer 17

long chains; straight, spiral, branched and ringed

Question 18

what is starch?

Answer 18

a large polysaccharide and is produced by the condensation of alpha-glucose units

Question 19

what are the two distinct components of starch?

Answer 19

amylose and amylopectin

Question 20

what structures does starch take?

Answer 20

spiral

Question 21

how is starch used?

Answer 21

by plants as an energy store, it is usually stored in the chloroplasts of leaves

Question 22

how is glucose stored?

Answer 22

as starch as it doesn’t affect water potential, it can also not diffuse out of the cell and can be stored in a small place

Question 23

what is the iodine test for starch?

Answer 23

the test from which tests the presence of starch.
1) add a few drops of iodine solution (which is orange) to a sample
2) if starch is present, the solution interacts with the starch molecules and turns the sample blue-black

Question 24

what is glycogen?

Answer 24

the animal kingdoms equivalent to starch, animals use glycogen as a store of energy.

Question 25

how is glycogen formed?

Answer 25

by the condensation of alpha-glucose units

Question 26

what are features of glycogen?

Answer 26

firstly, it is very similar structured to starch but is far more branched with a lot more 1-6 bonds.
-it is insoluble
-it is never found in plants
-used as a storage molecule for the same reason starch is used in plants

Question 27

how can we breakdown glycogen?

Answer 27

it is necessary to breakdown glycogen by hydrolysis in the presence of an enzyme

Question 28

what is cellulose?

Answer 28

it is an incredibly long polysaccharide with no branches, its bonds are beta-1-4 bonds

Question 29

what are features of cellulose?

Answer 29

-very different from both starch and glycogen
-it is not a storage molecule
-used in plant cell walls to assist in maintaining the rigidity of the plant
-most animals cannot digest it as it is too hard to breakdown
-in our diet we refer to cellulose as fibre

Question 30

how is cellulose formed?

Answer 30

by the condensation of beta-glucose monomers, not alpha-glucose like glycogen and starch

Question 31

what is lactose?

Answer 31

the main sugar in milk, small children produce lots of lactose in order to digest this disaccharide

Question 32

where does lactose travel through the body?

Answer 32

the small intestine and into the colon

Question 33

what happens if undigested glucose reaches there colon?

Answer 33

bacteria, which live in the colon, will use it as food for themselves however when they digest this lactose they produce significant gas, causing nausea, diarrhoea, bloating, cramps and wind - this is LACTOSE INTOLERANCE

Question 34

what are reducing sugars?

Answer 34

all monosaccharides are known as reducing sugars, meaning they can donate electrons in a chemical reaction

Question 35

what disaccharides are reducing sugars?

Answer 35

lactose and maltose, sucrose is not

Question 36

Benedict’s test for reducing sugars…

Answer 36

a chemical called ‘Benedict solution’ is used to test reducing sugars, the solution turns into a deep brick-red colour if the solution is in the presence of a reducing sugar

Question 37

what are the precipitate colours depending on concentration?

Answer 37

very low - green
low - yellow
medium - orange
high - brick red

Question 38

how can we test the presence of non-reducing sugars?

Answer 38

using the Benedict’s test also