1. Biological Molecules - Carbohydrates

Question 1

Name 3 common monosaccharides?

Answer 1

-Glucose
-Galactose
-Fructose

Question 2

What forms a glycosidic bond?

Answer 2

A condensation reaction

Question 3

What is maltose made from?

Answer 3

α-glucose + α-glucose

Question 4

What is sucrose made from?

Answer 4

α-glucose + α-fructose

Question 5

What is lactose made from?

Answer 5

α-glucose + β-galactose

Question 6

What is the difference between α-glucose and β-glucose?

Answer 6

α-glucose has the OH groups in line, β-glucose has the OH groups diagonal

Question 7

What causes the colour change in a benedicts test?

Answer 7

Blue to brick red indicates electrons have been donated to the Cu2+ ions in benedicts solution.

Question 8

What is a reducing sugar?

Answer 8

A sugar that donates electrons.

Question 9

How do you test for reducing sugars?

Answer 9

-Add benedicts to solution
-Heat in a water bath at 80C for 5 minute
-Record colour change

Question 10

How do you test for non-reducing sugars?

Answer 10

-Add HCl to solution and swirl to mix
-Place in a water bath at 80C for 5 minutes
-Remove and allow to cool
-Add 2 spatulas of sodium hydrogencarbonate
Add benedicts
-Place back in water bath for 5 minutes
-Record colour change

Question 11

What are the non-reducing sugars?

Answer 11

Sucrose and lactose

Question 12

What is released during a condensation reaction?

Answer 12

A water molecule

Question 13

What 2 things happen during a condensation reaction?

Answer 13

-A water molecule is released
-A new covalent bond is formed

Question 14

What 2 things happen during a hydrolysis reaction?

Answer 14

-Water molecule is used
-A new covalent bond is broken

Question 15

What are 3 polysaccharides?

Answer 15

Starch
Glycogen
Cellulose

Question 16

What is starch made from?

Answer 16

α-glucose

Question 17

What is glycogen made from?

Answer 17

α-glucose

Question 18

What is cellulose made from?

Answer 18

β-glucose

Question 19

Is starch branched or unbranched?

Answer 19

Both.

Question 20

What is starch’s branched structure called?

Answer 20

Amylopectin

Question 21

What is starch’s unbranched structure called?

Answer 21

Amylose

Question 22

Which glycosidic bond(s) does starch contain?

Answer 22

Both 1-4 and 1-6 glycosidic bonds

Question 23

What is starch in regards to it having an unbranched structure?

What is the benefit of this?

Answer 23

Coiled - meaning it can be compact and store a lot of energy.

Question 24

What forms when starch is hydrolysed?

Answer 24

α-glucose

Question 25

What does a branched structure of starch mean?

Answer 25

It means more enzymes can act upon it, allowing lots of glucose to be released quickly.

Question 26

Which glycosidic bond does amylose have?

Answer 26

1-4 glycosidic bond

Question 27

Which glycosidic bond does amylopectin contain?

Answer 27

1-4 and occasional 1-6 glycosidic bonds

Question 28

What are the percentages of each starch structure in starch?

Answer 28

-20% amylose -80% amylopectin

Question 29

What is a 1-4 glycosidic bond?

Answer 29

A bond between carbon 1 and carbon 4.

Question 30

Which carbohydrate is the energy store in plants?

Answer 30

Starch

Question 31

Which carbohydrate is the energy store in animals and fungi?

Answer 31

Glycogen

Question 32

What is the difference between starch and glycogen?

Answer 32

Glycogen does not have amylose or amylopectin, instead just a branched and unbranched structure.

Question 33

What is cellulose the polymer of?

Answer 33

β-glucose

Question 34

What does cellulose consist of (structure wise)?

Answer 34

Straight, unbranched chains which run parallel to one another.

Question 35

Which glycosidic bond(s) does cellulose contain?

Answer 35

Only 1-4 glycosidic bonds.

Question 36

Give 5 features of starch that makes it a good storage molecule:

Answer 36

-Insoluble - doesn’t affect w.p of cell -Unbranched, coiled, compact -Polymer of α-glucose -Highly branched - fast breakdown and release of glucose -Large molecule - can not diffuse out of cell easily

Question 37

What forms between adjacent cellulose chains, in turn forming what?

Answer 37

Hydrogen bonds form between adjacent chains, forming microfibrils.

Question 38

What are microfibrils?

Answer 38

They are the strong fibres that are made of many cellulose chains that are held together by hydrogen bonds.

Question 39

What is the benefit of a carbohydrate being a polymer of α-glucose?

Answer 39

Can provide respiratory substrate.

Question 40

What is the structure of amylose and what does this mean?

Answer 40

It’s helical, so compact and more can be stored in cell.

Question 41

What is the function of the spherical (unbranched) structure of glycogen?

Answer 41

Compact, so more can be stored in cell.

Question 42

What is the function of the branched structure of glycogen?

Answer 42

Can be hydrolysed more rapidly.

Question 43

What is the function of the hydrochloric acid in a non-reducing sugars test?

Answer 43

To break the glycosidic bonds.

Question 44

What is added to the sample after the HCl in a non-reducing sugars test? Why?

Answer 44

Sodium hydrogen carbonate is added to neutralise the sample.