2.1.2 - Biological molecules

Question 1

Define the term ‘polymer’ ?

Answer 1

Polymer - A long chain molecule composed of a large number of individual units called monomers bonded together in a repeating pattern

Question 2

Define the term ‘monomer’ ?

Answer 2

Monomer - Individual molecules that make up a polymer

Question 3

Define the term ‘condensation reaction’ ?

Answer 3

Condensation reaction - A reaction between two molecules resulting in the formation of a larger molecule and the release of a water molecule

Question 4

Define the term ‘hydrolysis reaction’ ?

Answer 4

Hydrolysis reaction - The breakdown of a larger molecule into two smaller molecules requiring the addition of a water molecule

Question 5

What elements are carbohydrates made of ?

Answer 5

C, H and O

Question 6

What elements are lipids made of ?

Answer 6

C, H and O

Question 7

What elements are proteins made of ?

Answer 7

C, H, N, O and S

Question 8

What elements are nucleic acids made of ?

Answer 8

C, H, N, O and P

Question 9

What are the properties of water ?

Answer 9

• Water is a metabolite
• Water is an important solvent
• Water has a high boiling point/ specific heat capacity
• Water has a high latent heat of vaporisation
• Water has a strong cohesion/ surface tension

Question 10

Explain how water is a metabolite ?

Answer 10

Water is a metabolite in many chemical reactions such as condensation and hydrolysis reactions

Question 11

Explain how water is a solvent ?

Answer 11

• Water is a solvent in which metabolic reactions occur
• It readily dissolves numerous substances and allows for effective transport of substances

Question 12

Explain why water has a high boiling point/ specific heat capacity ?

Answer 12

• Due to hydrogen binds, more energy is required to raise the temperature of water
• This allows water to act as a buffer against drastic temperature change

Question 13

Name examples where water acts as a buffer to drastic temperature change ?

Answer 13

• Majority of organisms are mostly made up of water buffering them against drastic temperature change
• Aquatic environments are temperature-stable as water acts as a buffer against drastic temperature change

Question 14

Explain how water has a high specific latent heat of vaporisation ?

Answer 14

• Due to hydrogen bonds, more energy is required to overcome bonds between water molecules and change the state of water
• This allows water to act as a coolant

Question 15

Name an example where water acts a coolant ?

Answer 15

When we sweat, more heat is used from our body to evaporate the sweat off our skin providing a cooling effect

Question 16

Explain how water has a strong cohesion/ surface tension ?

Answer 16

• This supports columns of water in xylem of plant setting up a transpiration stream
• This provides surface tension when water meets air ( ie. allows water to act as a habitant and support small organisms such as pond skaters )

Question 17

Define the term ‘monosaccharide’ ?

Answer 17

Monosaccharide - A single sugar molecule

Question 18

Name examples of monosaccharides ?

Answer 18

• Glucose ( alpha and beta )
• Fructose
• Galactose

Question 19

Define the term ‘polysaccharide’ ?

Answer 19

Polysaccharide - A long-chain polymer made up of a large number of sugar monomers / monosaccharides chemically joined together

Question 20

What is a hexose monosaccharide ?

Answer 20

A monosaccharide composed of six carbon toms

Question 21

Name examples of hexose monosaccharides ?

Answer 21

• Alpha glucose
• Beta glucose

Question 22

Draw the displayed formula of Alpha and Beta Glucose ?

Answer 22

Question 23

What is a pentose monosaccharide ?

Answer 23

A monosaccharide composed of five carbon atoms

Question 24

Name examples of pentose monosaccharides ?

Answer 24

• Ribose

Question 25

Define the term 'disaccharide' ?

Answer 25

Disaccharide - A molecule composed of two monosaccharides joined together by a glycosidic bond

Question 26

Name examples of disaccharides ?

Answer 26

- Sucrose - Maltose - Lactose

Question 27

Name the monosaccharides that the disaccharides sucrose, lactose and maltose are composed of ?

Answer 27

- Sucrose = fructose + glucose - Lactose = galactose + glucose - Maltose = glucose + glucose

Question 28

Explain what happens during a condensation reaction between two monosaccharides ?

Answer 28

- During a condensation reaction, a hydroxyl group from one monosaccharide and a hydrogen atom from another monosaccharide is removed - This leads to the elimination of a water molecule and the formation of a glycosidic bond

Question 29

What is the name of the bon that forms between monosaccharides ?

Answer 29

A glycosidic bond

Question 30

Explain what happens during the hydrolysis of a disaccharides ?

Answer 30

- During a hydrolysis reaction, a single water molecule is added to a disaccharide to break the glycosidic bond between the monosaccharides - This results in two individual monosaccharides

Question 31

Draw a diagram to represent the formation of a disaccharide and glycosidic bond ?

Answer 31

Question 32

What is starch ?

Answer 32

A polymer of alpha glucose which is an energy store in plants

Question 33

What are the two types of starch ?

Answer 33

- Amylose - Amylopectin

Question 34

Explain the structure of amylose ?

Answer 34

- Amylose is formed by alpha glucose molecules joining together only by 1-4 glycosidic bonds - This forms a helix shape ( making it compact and less soluble than glucose )

Question 35

Explain the structure of amylopectin ?

Answer 35

- Same as amylose and additionally some glycosidic bonds form between carbon 1 and 6 on two glucose molecules - This results in a more branched structure ( which can be hydrolysed to release more glucose molecules )

Question 36

Explain the effect of the helix shape of starch/ glycogen ?

Answer 36

The helix-shaped structure causes it to be more compact so more glucose can be stored in a smaller volume

Question 37

Explain the effect of starch/ glycogen being branched ?

Answer 37

Each end can be hydrolysed to release glucose for respiration/ transport

Question 38

Explain the effect of starch/ glycogen being insoluble ?

Answer 38

- Too large to leave the cell - Does not affect the water potential of the cell/ cause cell lysis

Question 39

Explain the effect of glycogen being more highly branched than starch ?

Answer 39

- This means it has more ends which can be hydrolysed to release more glucose at a faster rate - This allows glycogen to combat animals higher metabolic rate which requires more glucose due to being mobile unlike plants

Question 40

What is glycogen ?

Answer 40

A polymer of alpha glucose which is an energy store in animals

Question 41

Explain the structure of glycogen ?

Answer 41

- It is helix shaped - It is insoluble - It is more highly branched than starch ( both amylose/ amylopectin )

Question 42

What is cellulose ?

Answer 42

A polymer of beta glucose resulting in straight, unbranched chains

Question 43

Explain the structure of cellulose ?

Answer 43

- Cellulose is a polymer of beta glucose resulting in straight, unbranched chains - Each cellulose polymer cab form hydrogen bonds with parallel molecules - Cellulose molecules are bundled into microfibrils which are grouped into fibres

Question 44

Explain how the structure of cellulose aids it function ?

Answer 44

This results in the rigidity of the cell wall, providing mechanical strength which prevents cell lysis

Question 45

What are the two different types of sugars ?

Answer 45

- Reducing sugars - Non-reducing sugars

Question 46

What are reducing sugars ?

Answer 46

- Sugars that can reduce another molecule/ donate electrons - All monosaccharides and some disaccharides are reducing sugars

Question 47

What are non-reducing sugars ?

Answer 47

- Sugars that cannot reduce another molecule/ donate electrons

Question 48

Name the test used to identify reducing sugars in a sample ?

Answer 48

Testing using Benedict's Reagent

Question 49

What is Benedict's Reagent ?

Answer 49

Copper ( II ) Sulphate

Question 50

Describe the test for reducing sugars ?

Answer 50

1 ) Place sample in a boiling tube 2 ) Add an equal volume of Benedict's Regent into the boiling tube 3 ) Heat the mixture gently in a electric water bath for five minutes

Question 51

Explain how Benedict's Reagent helps identify reducing sugars in a sample ?

Answer 51

- Reducing sugars react with Benedict's Reagent causing Cu2+ ions to be reduced to Cu+ ions - This causes a brick-red precipitate to form/ CuO

Question 52

Explain how testing for reducing sugars is a quantitive test ?

Answer 52

- The more reducing sugars present, the more precipitate forms as more Cu2+ ions are reduced to Cu+ ions - Therefore, colour seen will depend on concentration of reducing sugars present

Question 53

Explain why non-reducing sugars will no produce a positive result when tested with Benedict's Reagent ?

Answer 53

Non-reducing sugars don't react with Benedict's Reagent and therefore will produce a negative result

Question 54

Describe how to test for non-reducing sugars ?

Answer 54

- Boil non-reducing sugars/ sample with dilute hydrochloric acid ( this will cause non-reducing sugars to be hydrolysed and break down into its monosaccharides/ reducing sugars ) - Test for presence of reducing sugars using Benedict's Reagent

Question 55

Describe the test for the presence of starch ?

Answer 55

- Add a few drops of iodine solution ( iodine dissolve in potassium iodide ) to the sample - Mix it with the sample

Question 56

What is a positive and negative result when testing for the presence of starch ?

Answer 56

- If it changes form yellow/brown to blue/black it is positive - If it does not change it is negative