3.1.1/2 Monomers and Polymers / Carbohydrates

Question 1

What is a monomer? (1)

Answer 1

A single unit that can create larger molecules

Question 2

What is a polymer? (1)

Answer 2

Repeating units of monomers bonded together

Question 3

Give three types of monomers found in biological molecules. (1)

Answer 3

Monosaccharides, amino acids and nucleotides

Question 4

What is a condensation reaction? (3)

Answer 4

The joining of two molecules creating a chemical bond whilst removing water

Question 5

What is a hydrolysis reaction? (3)

Answer 5

Breaking the chemical bonds between the molecules and involving the use of water

Question 6

Three examples of monosaccharides (3)

Answer 6

Glucose
Galactose
Fructose

Question 7

Three examples of disaccharides (3)

Answer 7

Maltose
Lactose
Sucrose

Question 8

Three examples of polysaccharides (3)

Answer 8

Glycogen
Starch
Cellulose

Question 9

What is an isomer? (1)

Answer 9

When it has the same molecular formula but different structure

Question 10

What is the difference between alpha and beta glucose?

Answer 10

In alpha glucose, the hydrogen atom (H) is at the top and the hydroxyl group (OH) is at the bottom and vice versa for beta glucose.

Question 11

What is a disaccharide? (3)

Answer 11

It is made up of two monosaccharides that are joined together by a glycosidic bond and formed in a condensation reaction.

Question 12

Starch
Monomers? Bond between monomers? Function? Location? Structure? Explanation of how structure leads to function?
(6)

Answer 12

• Alpha glucose
• 1-4 glycosidic bonds in amylose.1-4 and 1-6 glycosidic bonds in amylopectin
• It stores glucose
• Found in plant cells e.g. chloroplasts
• Made of 2 polymers:
amylose- unbranched helix & amylopectin- a branched molecule
• Helix can compact to fit a lot of glucose in a small space. Branched structure increases surface area for rapid hydrolysis back to glucose.
Insoluble- won’t affect water potential

Question 13

Cellulose
Monomers? Bond between monomers? Function? Location? Structure? Explanation of how the structure leads to function?
(6)

Answer 13

• Beta glucose
• 1-4 glycosidic bonds
• Structure strength for cell wall
• Plants -Cell wall
• Polymer forms long, straight chains. Chains are held in parallel by many hydrogen bonds to form fibrils.
• Many hydrogen bonds provide collective strength. Insoluble- won’t affect water potential

Question 14

Glycogen
Monomers? Bond between monomers? Function? Location? Structure? Explanation of how structure leads to the function?
(6)

Answer 14

• Alpha glucose
• 1-4 and 1-6 glycosidic bonds
• Store of glucose
• Animals - mainly in muscle/liver cells
• A highly branched molecule
• Branched structure increases surface area for rapid hydrolysis back to glucose. Insoluble- won’t affect water potential

Question 15

Test for starch

Answer 15

Add iodine
A positive test- solution turns from orange to blue/black

Question 16

Test for reducing sugars

Answer 16

Add Benedict’s reagent and heat
A positive test- solution from blue to green, yellow, orange or brick red
The more red, the higher the concentration of reducing sugar.

Question 17

Test for non-reducing sugars

Answer 17

Following a negative Benedict’s test- solution remains blue
Add acid and boil
Cool the solution then add an alkali to neutralise
Add Benedict’s reagent and heat
A positive test- solution from blue to orange/brick red

Question 18

Test for proteins

Answer 18

Add biuret
Positive- solution turns from blue to purple

Question 19

Test for lipids

Answer 19

Dissolve the sample in ethanol
Then add distilled water
Positive test- white emulsion forms