| Date | May 2017 | Marks available | 1 | Reference code | 17M.3.sl.TZ1.12 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Describe | Question number | 12 | Adapted from | N/A |
Question
Sugars exist in both straight chain and ring forms.
Biodegradable plastics produced from starch present one solution to the environmental problem created by the use of large quantities of plastics.
Deduce the straight chain structure of ribose from its ring structure drawn in section 34 of the data booklet.
Using the partial structure given, complete the structural formula of the molecule formed from the condensation of two cyclic -glucose molecules.
Constructing models that allow visualizations of the stereochemistry of carbohydrates is essential to understand their structural roles in cells.
Describe how Haworth projections help focus on the position of attached groups.
State one advantage of starch based polymers besides being biodegradable.
Biodegradable boxes made from polylactic acid, PLA, disintegrate when exposed to water.
State the formula of the product formed when water reacts with PLA.
Markscheme
All OH groups must be on the same side.
Accept structures with chiral carbon atoms shown as C or C* instead of crosses.
[1 mark]
Accept –O– in a straight line provided both H’s are above the plane.
[1 mark]
«allow» 3-D perspective of structures «of cyclic monosaccharide molecules»
OR
«show» cis/same side arrangement of «attached» groups
OR
«show» trans/opposite side arrangement of «attached» groups
OR
«make» carbon and hydrogen implicit
[1 mark]
abundant/renewable/allows use of «local» vegetation
OR
less use of fossil fuel/oil based plastics
OR
air permeable/better breathing of products
OR
«can be» mixed/blended with synthetic polymers
Do not accept answers related to biodegradable examples.
Ignore any reference to cost.
Accept “carbon neutral/do not contribute to global warming”.
Accept “require less energy to produce”.
Accept “do not produce toxic products”.
[1 mark]
HO–CH(CH3)–COOH/CH3CH(OH)COOH
Do not accept C3H6O3.
Do not accept OH–CH(CH3)–COOH.
[1 mark]
Examiners report
Syllabus sections
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18M.3.sl.TZ1.8a:
State the specific type of linkage formed between α-glucose fragments in both maltose and amylose.
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16N.3.sl.TZ0.9b:
The structures of two molecules, X and Y, are shown below.
(i) Justify why both these molecules are carbohydrates.
(ii) Distinguish between these molecules in terms of their functional groups.
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17M.3.sl.TZ2.10a:
Identify the functional groups which are present in only one structure of glucose.
- 19N.3.hl.TZ0.15c: Explain why maltose, C12H22O11, is soluble in water.
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17M.3.sl.TZ1.12a.ii:
Using the partial structure given, complete the structural formula of the molecule formed from the condensation of two cyclic -glucose molecules.
- 18N.3.sl.TZ0.8a: Name the type of link between the two monosaccharide residues.
- 18N.3.sl.TZ0.8b: Outline how the two monomer structures, galactose and glucose, differ.
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17M.3.sl.TZ1.12a.i:
Deduce the straight chain structure of ribose from its ring structure drawn in section 34 of the data booklet.
- 18N.3.hl.TZ0.10b: Outline how the two monomer structures, galactose and glucose, differ.
- 18N.3.hl.TZ0.10a: Name the type of link between the two monosaccharide residues.
- 19N.3.sl.TZ0.10c: Explain why maltose, C12H22O11, is soluble in water.
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19M.3.hl.TZ1.8a:
Draw the structure of the repeating unit of starch and state the type of linkage formed between these units.
Type of linkage:
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19M.3.hl.TZ2.12c:
Sketch the cyclic structures of the two monosaccharides which combine to form sucrose.
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19M.3.sl.TZ1.7a:
Draw the structure of the repeating unit of starch and state the type of linkage formed between these units.
Type of linkage:
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19M.3.sl.TZ2.8b:
Sketch the cyclic structures of the two monosaccharides which combine to form sucrose.
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19M.3.sl.TZ2.8a:
State the name of the functional group forming part of the ring structure of each monosaccharide unit.
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19M.3.hl.TZ2.12a:
State the name of the functional group forming part of the ring structure of each monosaccharide unit.
- 17N.3.sl.TZ0.9b: Draw the structure of galactose on the skeleton provided.
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17M.3.sl.TZ1.11a:
List the building blocks of triglycerides and carbohydrates.
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16N.3.sl.TZ0.9c:
Amylose is an unbranched polysaccharide composed of repeating units of glucose.
(i) Draw the structure of the repeating unit of amylose. Use section 34 of the data booklet.
(ii) Amylose is a major component of starch. Corn starch can be used to make replacements for plastics derived from oil, especially for packaging. Discuss one potential advantage and one disadvantage of this use of starch.
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17M.3.sl.TZ2.10b:
Sucrose is a disaccharide formed from -glucose and β-fructose.
Deduce the structural formula of sucrose.
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18M.3.sl.TZ2.6e:
Determine, to the correct number of significant figures, the energy produced by the respiration of 29.9 g of C5H10O5.
ΔHc (C5H10O5) = 205.9 kJ mol−1
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19M.3.hl.TZ1.8c:
Calculate the energy released, in kJ g−1, when 3.49 g of starch are completely combusted in a calorimeter, increasing the temperature of 975 g of water from 21.0 °C to 36.0 °C. Use section 1 of the data booklet.
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19M.3.sl.TZ1.7c:
Calculate the energy released, in kJ g−1, when 3.49 g of starch are completely combusted in a calorimeter, increasing the temperature of 975 g of water from 21.0 °C to 36.0 °C. Use section 1 of the data booklet.
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18M.3.sl.TZ1.8b:
A person with diabetes suffering very low blood sugar (hypoglycaemia) may be advised to consume glucose immediately and then eat a small amount of starchy food such as a sandwich. Explain this advice in terms of the properties of glucose and starch.
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17M.3.sl.TZ1.11b.i:
The drain pipe of a kitchen sink can become clogged by fatty acids, such as linoleic acid, C18H32O2, but not by the trisaccharide, raffinose, C18H32O16, containing the same number of carbon atoms.
Explain why raffinose is far more water soluble than linoleic acid.
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20N.3.hl.TZ0.8b(i):
The diverse functions of biological molecules depend on their structure and shape.
Deduce the straight chain structure of deoxyribose from its ring structure drawn in section 34 of the data booklet.
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20N.3.sl.TZ0.7b(ii):
The diverse functions of biological molecules depend on their structure and shape.
Sucrose is a disaccharide formed in the reaction of glucose with fructose.
Identify the reaction type and the newly formed functional group that joins the monosaccharide units in the product.
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20N.3.sl.TZ0.7b(i):
The diverse functions of biological molecules depend on their structure and shape.
Deduce the straight chain structure of deoxyribose from its ring structure drawn in section 34 of the data booklet.
