NAME:_______________________ OPTION GROUP:__________________

BIOLOGICAL MOLECULES 2

LIPIDS &

PHOSPHOLIPIDS

WORKBOOK

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REVISION CHECKLIST AND ASSESSMENT OBJECTIVES Instructions

Regular revision throughout the year is essential. It’s vital you keep a track of what you understand and what you don’t understand. This booklet is designed

to help you do this. Use the following key to note how well you understand the work after your revision. Put the letter R, A or G in the table. If you place an

R or an A then you should make a note of what you are struggling with and the end of this book under the relevant section and seek help with this.

Key R = Red. I am not confident about my knowledge and understanding A = Amber. I am fairly confident about my knowledge and understanding G = green. I am very confident about my knowledge and understanding

STUDY CHECKLIST AND ASSESSMENT OBJECTIVES

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The following points are what you need to know, revise and answer questions on.

Place an R, A or G when you have revised and make notes of what you do not understand in the relevant section at the back of this booklet.

Lipids and Phospholipids. Unit 1, Section 1 Topic f & g 1. Can you name the elements that make up a lipid and a phospholipid?

2. Can you name the components (monomers) of a lipid and phospholipid?

3. Can you name the reaction by which these monomers are joined together?

4. Can you draw an annotated diagram to show this reaction?

5. Can you state the name of the bond that joins the monomers of a lipid/phospholipid together?

6. Can you state the name of the reaction that will break the bonds between the monomers of a lipid/phospholipid? Can you state the products of this reaction? Can you draw an annotated diagram to show this reaction?

7. Can you describe the functions of lipids/phospholipids?

8. Can you explain the difference in a solid animal fat and a liquid plant oil in terms of the structure of the fatty acids?

9. Can you explain why an animal fat is solid at room temperature but a plant oil is a liquid.

10. Can you state the differences between lipids and phospholipids?

11. Can you state which type of fat when eaten in high amounts can course coronary heart disease.

12. Can you relate the terms hydrophobic and hydrophilic to the structure of a lipid and phospholipid?

13. Can you describe the chemical test for a lipid?

14. Can you explain if a lipid is a polymer or not?

Application of Knowledge

15. Can you apply your knowledge of lipids and phospholipids to unfamiliar scenarios?

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Assessment Objective Description AO1 Demonstrate knowledge and understanding of scientific ideas, processes, techniques and procedures.

AO2 Apply knowledge and understanding of scientific ideas, processes, techniques and procedures:

In a theoretical context

In a practical context

When handling qualitative data

When handling quantitative data

AO3 Analyse, interpret and evaluate scientific information, ideas and evidence, including in relation to issues, to:

Make judgments and reach conclusions

Develop and refine practical design and procedures

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WORD BANK Below is a list of some key words and phrases you will need to learn and understand in this lipid and

phospholipid section.

1. Amphiphilic.

2. Atheroma

3. Bilayer.

4. Carbon-carbon double bond.

5. Carbon-carbon single bond.

6. Carboxyl group

7. Cholesterol

8. Coronary Artery.

9. Ester Bond.

10. Fatty acid tails.

11. Fatty acid.

12. Glycerol.

13. HDL – high density lipoprotein.

14. Heart Disease.

15. Hydrocarbon chain.

16. Hydrophilic.

17. Hydrophobic.

18. Kink.

19. LDL – low density lipoprotein.

20. Lipid.

21. Monounsaturated.

22. Oil.

23. Partially soluble.

24. Phosphate head.

25. Phospholipid Bilayer

26. Polar head.

27. Polyunsaturated.

28. Saturated fatty acids.

29. Thrombus.

30. Triglyceride.

31. Unsaturated fatty acids.

WORD BANK

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1.0.1 Concept. Lipids are made from: 1 glycerol and 3 fatty acids. This means they are

not polymers as they are made up of different monomers.

The structure of these compounds is shown below:

Glycerol is a three-carbon compound with three

hydroxide (OH) groups attached to the carbons.

The three OH groups are the

positions at which the fatty

acids will covalently bond to

the glycerol.

Glycerol

1.1 f: THE STRUCTURE, FUNCTION & PROPERTIES OF

LIPIDS – PART 1

Fatty Acid

Carbocyclic

acid group Hydrocarbon chain with the end carbon

forming the methyl group (CH3)

A fatty acid consists of a carboxylic acid group and a long hydrocarbon

chain. The final carbon of the hydrocarbon chain has a CH3 group (called a

methyl group).

1.0 The monomers that make up a lipid

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1.0.2 Concept. The structure of fatty acids can differ based on:

The number of carbon atoms in the hydrocarbon chain.

The presence or absence of double bonds between carbon atoms of the

hydrocarbon tail.

In the table below are several different fatty acids showing the number of carbons and carbon-carbon

double bonds.

1.0.3 Concept. Fatty acids can be classified as saturated if there are no carbon-carbon

double bonds or as unsaturated if there are carbon-carbon double bonds.

Examples of saturated and unsaturated fatty acids are shown below:

Saturated fatty acid

Unsaturated fatty acids

Palmitic acid

Oleic acid

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1.0.4 Concept. Fatty acids have the following important features:

Saturated fatty acids have a straight hydrocarbon chain.

Saturated fatty acids have the maximum number of hydrogen atoms bonded to

each carbon atom of the hydrocarbon chain, i.e. 2 hydrogens per carbon atom with

3 hydrogens on the terminal carbon.

Unsaturated fatty acids have a kink in the hydrocarbon chain at each carbon-

carbon double bond.

Unsaturated fatty acids have 2 less hydrogen atoms for every carbon-carbon

double bond.

1.2.1 Concept. A lipid is formed by a condensation reaction where three fatty acids join to a single glycerol with the elimination of 3 water molecules to form ester bonds. A lipid is also called a triglyceride as it contains three fatty acids.

1.2 The formation of a lipid.

1. The OH group from the

carboxylic acid group of the fatty

acid aligns with the OH group on

the glycerol.

2. A condensation reaction

occurs with the release of three

water molecules

3. The three fatty acids are

bonded to the glycerol by an

ester bond. A triglyceride has

been formed.

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1.2.2 Other diagrams that represent the structure of a triglyceride.

Glyce

rol

Fatty Acid

Fatty Acid

Fatty Acid

Diagram showing the chemical detail

of the glycerol but with the fatty acids

represented by rectangles.

1.3.1 Concept. Lipids can be classified as saturated fats or unsaturated oils.

If a lipid is made from glycerol and a saturated fatty acid, the lipid is called a saturated fat. Saturated fats are obtained from animals.

If a lipid is made from glycerol and an unsaturated fatty acid, the lipid is called an unsaturated fat. Unsaturated fats are called oils and are obtained from plants.

1.3.2 Concept. All lipids are non-polar/hydrophobic molecules that cannot dissolve in water.

Diagram showing the glycerol and the

fatty acids represented by rectangles.

1.3 The classification of lipids

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1.5.1 Fats have the following functions. 1. Acts as an electrical insulator by forming the myelin sheath around the axons of nerve cells.

2. Acts as a thermal insulator by forming the subcutaneous fat under the skin.

3. Protection of body organs from physical damage.

4. Provides buoyancy for aquatic animals.

5. Acts as an energy store. Fats have twice the amount of energy for the same mass of a

carbohydrate. Fat is often used as an energy store in seeds.

6. Formation of the waxy cuticle on the surface of leaves to prevent water loss.

1.4. The Melting temperature of lipids

1.4.1 Concept. Saturated fats are solid at room temperature, but unsaturated oils are liquid at room temperature. Why?

The answer to the above questions is explained below:

1.5. The function of lipids

In a saturated fat the fatty acid chains

are straight. This means they can

pack close together. The

intermolecular forces (called

hydrophobic interactions) will be

strong. Room temperature will be

insufficiently high in heat energy to

break these intermolecular forces, so

the fat remains as a solid.

In an unsaturated fat the fatty acid

chains are bent. This means they

cannot pack close together. The

intermolecular forces will be weak.

Room temperature will be

sufficiently high in energy to break

these intermolecular forces, so the

fat is a liquid oil.

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1.6. Coronary heart disease

1.6.1 Concept. A high intake of saturated fats is a contributory factor in heart disease. Saturated fats can increase the concentration of cholesterol in the blood. This can lead to high levels of a structure known as LDL (low density lipoprotein) which keeps cholesterol in the blood. LDL is often called bad cholesterol. High levels of LDL-cholesterol can cause the accumulation of fat, white blood cells and ions in the wall of coronary arteries. This causes them to narrow and harden so reducing the blood flow to the heart muscle – this can cause a heart attack. HDL (high density lipoprotein) aid the removal of cholesterol from the blood and are often called good cholesterol.

1.7. The test for a lipid

1.7.1 The test for a lipid is called the emulsion test. The emulsion test is performed as follows:

1. Add the lipid to ethanol. The lipid will dissolve in the ethanol 2. Add the ethanol/lipid mixture to water. The lipid will form a white emulsion.

1.8. The monomers that make up a phospholipid

1.8.1 Concept. Phospholipids are made from glycerol, 2 fatty acids and a phosphate group.

Phosphate

Phospholipids are lipids with a phosphate group in place of one fatty

acid chain. A phosphate group is shown below:

1.1 f: THE STRUCTURE, FUNCTION & PROPERTIES OF

PHOSPHOLIPIDS – PART 2

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1.9.1 Concept. A phospholipid is formed by a condensation reaction where two fatty acids and a phosphate group join to a single glycerol with the elimination of 3 water molecules to form ester bonds.

1.9.2 Concept. Phospholipids can be represented using different shapes. Some examples are shown below.

1.9. The formation of a phospholipid

A phospholipid

Glycerol and phosphate

group

Fatty acid tails

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1.10. The properties and function of phospholipids

1.10.1. Concept. Phospholipids are amphoteric – they have two contrasting properties. They are both hydrophilic (polar) and hydrophobic (non-polar).

Phospholipids have both polar and non-polar regions.

The phosphate and glycerol group are called the polar

or hydrophilic head while the fatty acid tails are called

the non-polar or hydrophobic tails. Phospholipids are

important molecules as the polar head can dissolve in

water, but the non-polar fatty acid tails cannot. This

allow phospholipids to form a bilayer which is the

basic structure cell membranes.

Phospholipids arranged in a

bilayer forming a membrane.

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1. Name the molecule present in all lipids

2. Is a lipid a polymer?

3. State the elements found in a lipid and phospholipid.

4. How many molecules of water will be released by the complete hydrolysis of a triglyceride.

5. Draw an annotated diagram below of the complete breakdown of a triglyceride.

ACTIVITIES/QUESTIONS ON SECTION 1.1 PART 1 & 2

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6. Are lipids fully digested in the human digestive system? Explain your answer.

7. Is cholesterol a lipid?

8. Where are lipids synthesised?

9. Compare the structure of a saturated and unsaturated fatty acid.

10. What group does the end carbon of a fatty acid form?

11. Compare the structure of a triglyceride and a phospholipid.

12. Draw a diagram to show a monounsaturated fatty acid with 21 carbons.

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13. Referring to the table below answer the following questions.

a. What effect does an increase in the number of double bonds have on the melting point of a

fatty acid?

b. What effect does an increase in the number of carbon atoms have on the melting point of a

fatty acid? Explain your answer.

c. Explain why most polyunsaturated oils are liquid at room temperature.

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14. The image below is of a phospholipid.

a. Label this image.

b. Does this phospholipid have any unsaturated fatty acids? Explain your answer.

c. Phospholipids were poured carefully into a petri dish containing water. Draw how the

phospholipids would arrange themselves in the diagram of the petri dish below. Explain your

answer.

d. The phospholipids from part c were added to a sealed bottle of water and shaken. Draw below

how the phospholipids would arrange themselves. Explain your answer.

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15. The images below are some examples of lipids or where lipids can be found in nature, organisms or

food. Image 1 = butter, image 3 = margarine, image 6 = Schwann cell, image 8 = cell membrane,

image 9 = a hormone found in males.

a. In image 5 can you suggest a suitable scientific name for labels A and B?

b. Can you suggest a scientific name for the arrangement of the molecules in image 8?

c. In organisms the arrangement of the molecules in image 8 does not form this “sheet” structure,

explain why.

d. Are there any biochemical differences/similarities between a lipid, fat and an oil?

1 2

4 A B 5 6

7 8 9

3

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e. Can you name the molecule in image 9 and the type of biological molecule it is?

f. How does the biochemical properties of the molecules in image 8 and image 6 differ from the molecules in the other images?

g. Can you suggest a melting temperature for the molecule in image 4 and 7? Can you provide a basic explanation for your answer?

16. Explain the advantage of seeds using fats as an energy store rather than carbohydrates.

17. Describe the structure of starch.

18. The diagrams show the structure of a glycerol molecule and a fatty acid molecule.

a. With the aid of similar diagrams draw a monoglyceride in the space below.

R

Glycerol

Fatty acid

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b. What does the “R” represent in the fatty acid structure shown above.