The diagram shows two biological molecules.
Identify, with a reason, the diagram that contains a lipid.
The diagram below shows a ribose monosaccharide.
Sketch a molecular diagram of deoxyribose.
List two of the chemical groups found in a generalised amino acid.
Identify, with a reason, the diagram that shows the structure of a saturated fatty acid.
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State the type of reaction that occurs between monosaccharides in order to form a polysaccharide.
Place these types of carbohydrate into decreasing order of molecular size.
tetrasaccharides
monosaccharides
polysaccharides
disaccharides
A disaccharide has the formula C12H22O11 and is pictured below.
Draw a ring around the chemical group that bonds two monosaccharides together.
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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List two properties of starch that make it an effective storage polysaccharide.
List two properties of cellulose that make it an effective structural polysaccharide.
Glycogen has a highly branched structure, which makes it ideal as a storage molecule in animal cells.
Describe how the branched structure of glycogen makes it an ideal energy storage compound in animals.
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Describe the composition of a triglyceride molecule.
The diagram shows a fatty acid.
(i) Identify the type of fatty acid shown in the diagram.
[1]
(ii) Give a reason for your answer to part (i).
[1]
The diagram shows a different fatty acid.
Describe and explain the properties of a lipid containing many of this type of fatty acid.
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The low oxygen content of lipids enables them to be more energy-dense forms of energy storage than carbohydrates.
Explain why.
Define the term 'metabolic water'.
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'.
Suggest why the lipids sector of the chart is so much larger than that of carbohydrates.
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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Define the term hydrophilic.
Describe the chemical properties of carbon that allow it to form many different types of molecules.
List three groups of carbon compounds upon which living organisms are based.
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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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|
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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.
1 markTwo 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 |
|
B |
|
C |
|
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.
2 marksAs 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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Explain the ability of oestradiol to pass through the phospholipid bilayer.
Explain how structure relates to function in carbohydrates and lipids.
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The 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]
Molecular 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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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.
The 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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Compare and contrast the compounds glycogen and starch.
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