Identify which of the diagrams below is a lipid, giving one reason why.
Sketch a molecular diagram of D-ribose.
List, using simplified notation, two of the chemical groups found in a generalised amino acid.
State, giving one reason, which diagram shows the structure of a saturated fatty acid.
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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.
State the specific type of bond in amylopectin that gives the molecule its highly branched structure.
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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Identify the two distinct parts of a typical fatty acid molecule.
The 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]
The 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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Define the term hydrophilic.
State two advantages of a carbon atom being able to form four bonds to neighbouring atoms.
List three carbon compounds upon which living organisms are based.
State 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.
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 |
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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.
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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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.
In the Jmol visualisation, black atoms are carbon, grey atoms are oxygen and white atoms are hydrogen.
Identify the type of molecule shown 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 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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Compare and contrast the compounds glycogen and starch.
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