2 marksIdentify, with a reason, the diagram below that contains a lipid.
2 marksSketch a molecular diagram of ribose.
2 marksList two of the chemical groups found in a generalised amino acid.
2 marksIdentify, with a reason, the diagram that shows the structure of a saturated fatty acid.
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1 markState the type of bond that forms between two sugar molecules in a disaccharide.
2 marksPlace these types of carbohydrate into decreasing order of molecular size.
tetrasaccharides
monosaccharides
polysaccharides
disaccharides
1 markA disaccharide has the formula C12H22O11 and is pictured below.
Draw a ring around the chemical group that bonds two monosaccharides together.
1 markGlucose, 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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2 marksList two properties of starch that make it an effective storage polysaccharide.
2 marksList two properties of cellulose that make it an effective structural polysaccharide.
1 markState the specific type of bond in amylopectin that gives the molecule its highly branched structure.
2 marksGlycogen 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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2 marksIdentify the two distinct parts of a typical fatty acid molecule.
2 marksThe diagram shows a fatty acid.
(i) Identify the type of fatty acid shown in the diagram.
[1]
(ii) State a reason for your answer in part i).
[1]
2 marksThe diagram shows a different fatty acid.
Use a tick (✔) in each table to identify words to describe the structure of the fatty acid shown.
Monounsaturated | Polyunsaturated | Saturated |
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All Cis | All Trans | Mixture of Cis- and Trans- |
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1 markThe low oxygen content of lipids enables them to be more energy-dense forms of energy storage than carbohydrates.
Explain why.
2 marksDefine the term 'metabolic water'.
1 markThe 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'.
Suggest why the lipids sector of the chart is so much larger than that of carbohydrates.
2 marksState 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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8 marksOne 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.
4 marksDraw a labelled molecular diagram of a triglyceride which contains one monounsaturated fatty acid.
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1 markDefine the term hydrophilic.
2 marksState two advantages of a carbon atom being able to form four bonds to neighbouring atoms.
3 marksList three carbon compounds upon which living organisms are based.
1 markState which part of metabolism is occurring at II in the flowchart below.
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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 |
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Contains α-glucose |
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Contains hydrogen bonds |
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Explain the name of the type of reaction that forms the carbohydrates in part (a) from their monomers.
State one feature of starch and explain how this feature allows it to act as a storage substance.
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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Sucrose is formed from monosaccharides X and Y.
The diagram below shows the structure of sucrose and monosaccharide Y.
Draw and identify monosaccharide X.
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.
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 |
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B |
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C |
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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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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.
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.
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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Draw a diagram of a section of a molecule of cellulose.
Your drawing should contain no fewer than three monomers joined together.
Outline why lipids are more suitable for long-term energy storage than carbohydrates in animals.
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2 marksThe following diagram shows the structure of a polysaccharide found in plant cells.
(i) Identify the polysaccharide pictured in the diagram.
[1]
(ii) Explain your answer at part i).
[1]
2 marksMolecular visualisation software such as Jmol can be used to depict biological molecules.
Identify the molecule in this Jmol visualisation.
2 marksThree 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.
2 marksThe tetrasaccharide stachyose has the molecular formula C24H42O21.
Describe two aspects of its molecular formula that identifies stachyose as a carbohydrate.
2 marksA 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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2 marksTypical 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.
4 marksThe diagram shows a cell with a role in storage.
(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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8 marksCompare and contrast the compounds glycogen and starch.
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