Syllabus Edition

First teaching 2023

First exams 2025

|

Carbohydrates & Lipids (HL IB Biology)

Exam Questions

2 hours34 questions
1a
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2 marks

Identify which of the diagrams below is a lipid, giving one reason why.

2-1-e-4-paper-2

1b
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2 marks

Sketch a molecular diagram of D-ribose.

1c
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2 marks

List, using simplified notation, two of the chemical groups found in a generalised amino acid.

1d
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2 marks

State, giving one reason, which diagram shows the structure of a saturated fatty acid.

2-1-e-4d-paper-2

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2a
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1 mark

State the type of bond that forms between two sugar molecules in a disaccharide. 

2b
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2 marks

Place these types of carbohydrate into decreasing order of molecular size.

  • tetrasaccharides
  • monosaccharides
  • polysaccharides
  • disaccharides

2c
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1 mark

A disaccharide has the formula C12H22O11 and is pictured below.

sucrose

Draw a ring around the chemical group that bonds two monosaccharides together.

2d
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1 mark

Glucose, galactose and fructose all have the same molecular formula but differ in their physical and chemical properties.

State the collective name for compounds like these, that have the same molecular formula but different properties. 

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3a
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2 marks

List two properties of starch that make it an effective storage polysaccharide.

3b
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2 marks

List two properties of cellulose that make it an effective structural polysaccharide. 

3c
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1 mark

State the specific type of bond in amylopectin that gives the molecule its highly branched structure. 

3d
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2 marks

Glycogen has an even more branched structure than amylopectin, which makes it ideal as an energy storage molecule in animal cells.

Describe how the branched structure of glycogen helps fulfil its role as a short-term energy storage compound. 

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4a
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2 marks

Identify the two distinct parts of a typical fatty acid molecule. 

4b
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2 marks

The diagram shows a fatty acid.5Q18GzYb_e-3b

(i)

Identify the type of fatty acid shown in the diagram.

[1]

(ii)

State a reason for your answer in part i).

[1]

4c
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2 marks

The diagram shows a different fatty acid. WAld1UrZ_e-3c

Use a tick (✔) in each table to identify words to describe the structure of the fatty acid shown.

Monounsaturated Polyunsaturated Saturated
     

All Cis All Trans Mixture of Cis- and Trans-
     

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5a
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1 mark

The low oxygen content of lipids enables them to be more energy-dense forms of energy storage than carbohydrates. 

Explain why.

5b
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2 marks

Define the term 'metabolic water'. 

5c
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1 mark

The pie chart gives the proportions of the main food groups in the yolk of a typical hen's egg, which serves as a source of nutrition for the growing embryo. This does not include the 'egg white'. e-4c-1

Suggest why the lipids sector of the chart is so much larger than that of carbohydrates. 

5d
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2 marks

State the type of bond, and the number of those bonds, between fatty acids and a glycerol molecule in a typical triglyceride molecule. 

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6a
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8 marks

One mark is available for clarity of communication throughout this question.

State, with an example in each case, four different ways in which lipids are used in nature. 

6b
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4 marks

Draw a labelled molecular diagram of a triglyceride which contains one monounsaturated fatty acid.

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7a
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1 mark

Define the term hydrophilic.

7b
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2 marks

State two advantages of a carbon atom being able to form four bonds to neighbouring atoms.

7c
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3 marks

List three carbon compounds upon which living organisms are based. 

7d
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1 mark

State which part of metabolism is occurring at II in the flowchart below.

2-1-e-1d-paper-2

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1a3 marks

The table below contains statements that could apply to three polysaccharides. Complete the table with a tick () in each box if the statement applies correctly

Statement Glycogen Cellulose Starch
Contains 1-6 links      
Contains α-glucose      
Contains hydrogen bonds      
1b2 marks

Explain the name of the type of reaction that forms the carbohydrates in part (a) from their monomers.

1c2 marks

State one feature of starch and explain how this feature allows it to act as a storage substance.

1d1 mark

Two molecules of a disaccharide are condensed together to form a larger sugar molecule. The chemical formula of the disaccharide is C12H22O11.

Deduce the formula of the resulting larger sugar molecule.

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2a2 marks

Sucrose is formed from monosaccharides X and Y.

The diagram below shows the structure of sucrose and monosaccharide Y.

q2a-2-2-carbohydrates-lipids-medium-ib-hl-biology-sq

Draw and identify monosaccharide X.

2b1 mark

The monosaccharides fructose and glucose have the same molecular formula, C6H12O6. However, their differing structures give them different properties; for example, fructose tastes sweeter than glucose.

Suggest one advantage to the food industry of this difference.

2c3 marks

Molecular analysis was carried out using various laboratory techniques to distinguish between samples of three different polysaccharides. Starch was separated into its constituent polysaccharides (amylose and amylopectin) before analysis. The results are shown in the table below.

Sample Branches per molecule Speed of hydrolysis / arbitrary units
A 87 35
B 1467 80
C 1780 98

The three samples were amylopectin, glycogen and amylose (not necessarily in that order).

Use your knowledge of polysaccharide structure to assign each sample to one of those three polysaccharides.

Sample Polysaccharide
A  
B  
C  
2d2 marks

Within animal cells, fats are used as a long-term energy storage. A carbohydrate, glycogen, is used as a short-term energy storage molecule as well.

Explain the benefits of having this kind of short-term storage system.

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3a2 marks

The diagram below shows an incompletely-drawn triglyceride molecule.

Complete the drawing to show a trans-monounsaturated fatty acid chain at position 1 of the glycerol molecule.q3a-2-2-carbohydrates-lipids-medium-ib-hl-biology-sq 

3b2 marks

As part of a 50-year study into health and diet, data was gathered in 1960 and 2000 for the numbers of deaths due to cardiovascular disease in a western European country. This data was compared to the percentage of energy provided by trans-fats in the diets of elderly men (aged 70 and above). Some of the research findings are shown below.

Year Proportion of dietary energy from trans-fats / % Deaths from cardiovascular disease in that year
1960 7 20 185
2000 1 15 542

Calculate the percentage decrease in numbers of deaths from cardiovascular disease between 1960 and 2000.

3c2 marks

Referring to the study described in (b), post-mortem investigations of some patients who had died from cardiovascular disease revealed that fatty deposits in their diseased arteries contained high concentrations of trans-fats.

Explain why this finding, though positively correlated, does not prove causation.

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4a4 marks

Draw a diagram of a section of a molecule of cellulose.

Your drawing should contain no fewer than three monomers joined together.

4b3 marks

Outline why lipids are more suitable for long-term energy storage than carbohydrates in animals.

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1a
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2 marks

The following diagram shows the structure of a polysaccharide found in plant cells.

gj15wkVE_h-1a

(i)

Identify the polysaccharide pictured in the diagram.

[1]

(ii)
Explain your answer at part i).

[1]

1b
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2 marks

Molecular visualisation software such as Jmol can be used to depict biological molecules. h-1b

Identify the molecule in this Jmol visualisation. 

1c
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2 marks

Three molecules of the same monosaccharide are joined in a line into a trisaccharide. 

The molecular formula of the monosaccharide is C5H10O5.

Deduce the formula of the resulting trisaccharide. 

1d
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2 marks

The tetrasaccharide stachyose has the molecular formula C24H42O21.

Describe two aspects of its molecular formula that identifies stachyose as a carbohydrate.

1e
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2 marks

A disaccharide has the formula C12H22O11

It is made up of two identical monosaccharides. 

Deduce the formula of the monosaccharides that form the disaccharide.

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2a
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2 marks

Typical energy content values of various food group molecules are given in the table below. 

Food Group Typical energy content / kJg-1
Protein 15
Carbohydrate 17
Fat 38


State the molecular feature of fats that allows them to contain more energy per gram than carbohydrates or proteins.

2b
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4 marks

The diagram shows a cell with a role in storage.

h-3b

(i)

Identify structures X, Y and Z in this diagram.

[3]

(ii)

Suggest which tissue this cell forms part of.

[1]

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3
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8 marks

Compare and contrast the compounds glycogen and starch. 

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