carbohydates

Question 1

state the elements present in carbohydrates

Answer 1

carbon
oxygen
hydrogen

Question 2

state the general formula of carbohydrates

Answer 2

(CH2O)n

Question 3

define monosaccharide, disaccharide and polysaccharide

Answer 3

monosaccharide - a single simple sugar
monosaccharide - molecule composed of two monosaccharides joined by a glyosidic bond
polysaccharide - a polymer made of many monosaccharide (sugar) monomers

Question 4

define pentose sugar and hexose sugar

Answer 4

pentose sugar - monosaccharide composed of 5 carbons

hexose sugar - monosaccharide composed of 6 carbons

Question 5

define triose and give an example

Answer 5

a monosaccharide composed of 3 carbons e.g glyceraldehyde

Question 6

define furanose ring and pyranose ring

Answer 6

furanose ring - 5 membered carbon ring e.g fructose

pyranose ring - 6 membered carbon ring e.g glucose

Question 7

define isomer

Answer 7

molecules with the same molecular formula but different structural formula

Question 8

describe the difference between alpha glucose and beta glucose

Answer 8

the hydrogen and hydroxyl groups of carbon 1 are reversed ( on alpha glucose H is above OH below)

Question 9

differences between alpha glucose and ribose

Answer 9

alpha glucose has a pyranose ring ribose has a furanose ring
glucose is used in starch and glycogen but ribose is used in RNA

Question 10

list 3 examples of disaccharide and the molecules they are composed of

Answer 10

maltose - two alpha glucose
lactose - alpha glucose and galactose
sucrose - alpha glucose and fructose

Question 11

State the properties and functions of glucose, fructose, galactose, maltose, sucrose and lactose. For each also state where they occur.

Answer 11

Glucose - monosaccharide used in respiration and to make polymers such as starch
Fructose - hexose sugar commonly found in fruit
Galactose - another hexose sugar
Maltose - found in barley
Sucrose - found in sugar cane and beet
Lactose - found in milk

Question 12

explain why alpha glucose links together to from starch whereas beta glucose links together to form cellulose

Answer 12

due to the difference in arrangement of the hydroxyl group of carbon 1.
1-4 glyosidic bonds of alpha glucose means each monomer is same way up, in beta glucose every other monomer is rotated 180 degrees

Question 13

list the two different polysaccharides that make up starch

Answer 13

amylose (1-4 glyosidic bonds)

amylopectin (1-4 and 1-6 glyosidic bonds)

Question 14

explain why glyosidic bonds are either 1-4 or 1-6

Answer 14

dependent on whether the bond is between the OH on carbon 1 and 4 or 1 and 6

Question 15

describe the structure of a cellulose fibre

Answer 15

several cellulose molecules produce a microfibil
several microfibrils hydrogen bond to form a marcrofibril
macrofibrils are laid down to form the cell wall

Question 16

describe the functions and properties of starch cellulose and glycogen

Answer 16

starch - coils into a helix amylose is unbrached and amylopectin is branched. compact and insoluble so good for storage. Used as a food storage in plants
cellulose - unbranched does not form helix - forms layers to provide strength for cell wall
glycogen - more branched than amylopectin, coils into helix compact and insoluble so used for food storage in animals and fungi