Biological molecules-Carbohydrates

Question 1

What are biological molecules?

Answer 1

molecules made and used by living organisms e.g. Carbohydrates,
Proteins, Lipids, DNA, ATP, Water, Inorganic Ions

Question 2

What are the functions of carbohydrates?

Answer 2

energy source (glucose in respiration)
energy store (starch in plants, glycogen in animals)
structure (cellulose in cell wall of plants)

Question 3

What are the building blocks for carbohydrates called?

Answer 3

monosaccharides

Question 4

Example of monosaccharides?

Answer 4

glucose (alpha and beta), galactose, fructose

Question 5

Formula for monosaccharides?

Answer 5

C6H12O6

Question 6

Difference between alpha and beta glucose?

Answer 6

on Carbon 1, alpha glucose has a OH group on the

bottom and beta glucose has a OH group on the top

Question 7

How are monosaccharides joined together?

Answer 7

condensation reaction (removing water) – between 2
OH groups

Question 8

Bond in carbohydrate?

Answer 8

glycosidic bond

Question 9

Example of disaccharides?

Answer 9

glucose + glucose = maltose, glucose + galactose = lactose,

glucose + fructose = sucrose

Question 10

Formula for disaccharides?

Answer 10

C12H22O11

Question 11

How are polymers separated?

Answer 11

hydrolysis (add water)

Question 12

What is a polysaccharide?

Answer 12

many monosacharrides joined by condensation reaction/glycosidic
bonds

Question 13

Example of polysaccharides?

Answer 13

Amylose (long chain of alpha glucose) which makes starch/glycogen

Cellulose (long chain of beta glucose) which makes cell wall in plants

Question 14

Functions of these polysaccharides

Answer 14

Starch & Glycogen used as Energy Stores (starch in plants, glycogen in animals), they are made out of
many alpha glucose which are used for respiration

Cellulose used to form Cell Wall in Plants, made out of many beta glucose

Question 15

Properties of Starch and Glycogen as energy stores?

Answer 15

Insoluble = do not affect water potential of the cell, do not diffuse out of the cell
Coiled/Branched = compact, more can fit into a cell
Branched/Chained = glucose removed from the end

Question 16

Structure of Cellulose?

Answer 16

 β-glucose arranged in a straight chain
 many cellulose chains are cross linked by hydrogen bonds to form microfibrils
 many microfibrils are cross linked to form marcrofibrils
 forms structure of cell wall
 strong material (prevents plant cell from bursting or shrinking)

Question 17

Test for starch?

Answer 17

add iodine, turns blue/black

Question 18

Test for reducing sugar?

Answer 18

heat with benedicts, turns brick red

Question 19

Test for non-reducing sugar?

Answer 19

heat with benedicts – no change
 therefore, add dilute hydrochloric acid (hydrolyses glycosidic bond)
 then add sodium hydrogencarbonate (neutralises solution)
 heat with benedict - turns brick red