| Date | November 2018 | Marks available | 1 | Reference code | 18N.3.hl.TZ0.10 |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Name | Question number | 10 | Adapted from | N/A |
Question
Lactose, found in milk and dairy products, is a disaccharide formed from two different monosaccharides. The structure of lactose is shown with numbered carbon atoms.
Starch and cellulose are both formed from glucose and have similar structures.
Name the type of link between the two monosaccharide residues.
Outline how the two monomer structures, galactose and glucose, differ.
Outline the difference between their structures.
Outline why cellulose is an essential part of human diet.
Markscheme
«1,4-»glycosidic ✔
Do not accept “glucosidic”.
H and OH are reversed/in different positions on C-4 ✔
C-4 must be specified.
Do not penalize if reference is made to H and OH above and below ring/in alpha and beta positions on C-4 incorrectly.
Starch: α«-glucose/links»
AND
Cellulose: β«-glucose/links» ✔
Accept “Starch: coiled/spiral structure OR cross-links AND Cellulose: uncoiled OR straight chains/linear polymer OR no/few cross-links”.
Any two of:
helps food pass through intestine
OR
adds bulk/dietary fibre ✔
reduces appetite
OR
helps prevent obesity ✔
prevents constipation
OR
reduces risk of hemorrhoids/diverticulosis/Crohn’s disease/irritable bowel syndrome/bowel cancer ✔
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.
- 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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17M.3.sl.TZ1.12b:
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.
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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.
-
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.
