Biological Molecules - Carbohydrates

Question 1

Elements present in carbohydrates

Answer 1

Carbon, hydrogen and oxygen

Question 2

General formula of monosaccharides

Answer 2

Cn(H2O)n

Question 3

Difference between pentose and hexose sugars

Answer 3

Pentose has 5 carbons in the chain, hexose has 6

Question 4

Example of triose, pentose and hexose sugars

Answer 4

Triose: glyeraldehyde -formed during respiration of glucose
Pentose: Ribose - RNA in nucleotides
Hexose: glucose - all living cells as used in respiration
Fructose - fruit

Question 5

Difference between alpha and beta glucose

Answer 5

Beta glucose has the hydroxyl group on C1 above the ring

Question 6

Define isomer

Answer 6

Structurally different but chemically exactly the same - eg. Alpha and beta glucose

Question 7

General formula of disaccharides

Answer 7

Cn(H2O)n-1

Question 8

Bond formed in maltose

Answer 8

a 1~4 glycosidic bond

Question 9

Components and uses of sucrose

Answer 9

a-glucose and fructose

Used for storage as sugar cane or beet and transported in phloem

Question 10

Components and uses of lactose

Answer 10

a-glucose and galactose

Used- milk sugar as difficult to hydrolyse, providing a slow release of sugars to babies

Question 11

Components and uses of maltose

Answer 11

a-glucose and a-glucose

Found in intestine and germinating seeds, intermediate in hydrolysis of starch.

Question 12

Cellulose structure

Answer 12

Beta glucose - therefore forms straight chain as alternate are turned upside down. Hydrogen bonds between cellulose chain form microfibres then macro fibrils and cellulose fibres. Held together with pectins.

Question 13

Cellulose properties

Answer 13

High tensile strength
Fully permeable to water
Resistant to hydrolysis
Supports a plant when turgid

Question 14

Glycogen structure

Answer 14

Made up of alpha glucose with more branches than amylopectin and more 1,6 glycosidic bonds making it more compact

Question 15

Glycogen properties

Answer 15

Insoluble in water
Energy storage in animals
Similar to amylopectin
Hydrolysed very quick to glucose as more 'ends'
Storage polysaccharide in animals

Question 16

Starch structure

Answer 16

Made up of alpha glucose.
Amylose joined by 1,4 glycosidic bond forms helix stabilised by hydrogen bonds
Amylopectin joined by 1,6 glycosidic bonds and so has branched structure

Question 17

Starch functional points

Answer 17

Insoluble in water
Doesn't affect water potential of cells
Compact molecule
Doesn't diffuse out of cells
Ends can easily be broken off for respiration, more in amylopectin so hydrolyses faster

Question 18

Test for starch

Answer 18

Test with iodine solution, positive results turns blue-black

Question 19

Hydrolysis

Answer 19

Chemical reaction in which a water molecule is needed to break a complex molecule into small molecules. Can be done with enzymes (eg. maltase) or heating with acid.