B1.1 Carbohydrates and lipids
Practice exam-style IB Biology questions for Carbohydrates and lipids, aligned with the syllabus and grouped by topic.
Question 1
A carbon atom is able to form diverse biological molecules. What property of carbon is most directly responsible for this diversity?
A.
It is always found in straight chains.
B.
It has a complete outer electron shell.
C.
It can form up to four covalent bonds.
D.
It forms ionic bonds with water molecules.
Question 2
What reaction links two monosaccharides to form a disaccharide?
A.
Hydrolysis with release of water
B.
Reduction with formation of oxygen
C.
Condensation with release of water
D.
Oxidation with uptake of carbon dioxide
Question 3
What happens to water during hydrolysis of a polysaccharide?
A.
It is converted into carbon dioxide and oxygen.
B.
It is oxidized to provide energy for digestion.
C.
It is released when a new glycosidic bond forms.
D.
It is split and contributes –H and –OH to the products.
Question 4
A substance dissolves in a non-polar solvent but is only sparingly soluble in water. What class of biological molecule does this describe?
A.
Monosaccharide
B.
Lipid
C.
Nucleotide
D.
Polypeptide
Question 5
Define a monomer.
[1]
State the type of reaction that joins monosaccharides to form a polysaccharide.
[1]
State the name of the covalent bond formed between monosaccharides.
[1]
Question 6
A monosaccharide ring diagram contains five carbon atoms and one oxygen atom. How should this monosaccharide be classified?
A.
Polysaccharide
B.
Pentose
C.
Hexose
D.
Disaccharide
Question 7
What feature of glycogen makes it suitable for rapid mobilization of glucose in animals?
A.
It dissolves freely as individual glucose molecules.
B.
Many branches provide many chain ends for enzyme action.
C.
Straight chains form hydrogen-bonded microfibrils.
D.
Its monomers are beta-glucose molecules.
Question 8
What structural feature of cellulose allows long chains to form strong bundles?
A.
Frequent branches produce many compact coils.
B.
Alpha-glucose monomers form helical chains.
C.
Fatty acid tails exclude water from the chains.
D.
Alternating beta-glucose monomers produce straight chains.
Question 9
What cell-surface molecule is directly involved in ABO blood-group recognition?
A.
A triglyceride droplet inside the erythrocyte
B.
A cellulose microfibril in the plasma membrane
C.
A free glucose molecule dissolved in plasma
D.
A glycoprotein with a specific terminal carbohydrate arrangement
Question 10
How does a monounsaturated fatty acid differ from a saturated fatty acid?
A.
It has beta-glucose monomers joined by glycosidic bonds.
B.
It has one C=C bond in the hydrocarbon chain.
C.
It has no carbon-carbon bonds in the hydrocarbon chain.
D.
It has more than one phosphate-containing group.
Question 11
What property of triglycerides makes them suitable for long-term energy storage in adipose tissue?
A.
They are cross-linked by hydrogen bonds into fibres.
B.
They are polymers of glucose.
C.
They are highly soluble in blood plasma.
D.
They are energy-rich and hydrophobic.
Question 12
State the name of the reaction used in digestion to break polysaccharides into monosaccharides.
[1]
Describe the role of water in this reaction.
[1]
State one reason why digestion into monomers is useful to organisms.
[1]
Question 13
State one property of glucose that allows it to be transported in blood plasma.
[1]
Explain why storing large amounts of free glucose in a cell would be a problem.
[1]
Question 14
Define lipid in terms of solubility.
[1]
Give one example of a lipid.
[1]
Question 15
Define a saturated fatty acid.
[1]
Distinguish monounsaturated and polyunsaturated fatty acids.
[1]
Question 16
A student measured melting points of four fatty acids with the same chain length but different numbers of C=C bonds.
| Fatty acid | C=C bonds / molecule | Melting point / °C |
|---|---|---|
| Stearic acid | 0 | 69.6 |
| Oleic acid | 1 | 13.4 |
| Linoleic acid | 2 | -5.0 |
| Linolenic acid | 3 | -11.0 |
Identify the fatty acid with the highest melting point.
[1]
Describe the relationship between number of C=C bonds and melting point.
[1]
Suggest why this relationship occurs.
[1]
Question 17
The figure shows ring diagrams of four monosaccharides.
Identify one hexose shown in the figure.
[1]
Identify one pentose shown in the figure.
[1]
Explain how the ring diagrams can be used to distinguish pentoses from hexoses.
[1]
Question 18
What arrangement is expected when phospholipids are placed in water?
A.
A compact coil stabilized by alpha-glucose branches
B.
A bilayer with hydrophobic tails facing water on both sides
C.
A bilayer with hydrophilic heads facing water and hydrophobic tails inward
D.
A chain of monomers joined by glycosidic bonds
Question 19
A molecule contains glycerol linked to two fatty acids and one phosphate-containing group. What molecule is it?
A.
Glycogen
B.
Triglyceride
C.
Phospholipid
D.
Cellulose
Question 20
Why do many plant oils remain liquid at ordinary room temperature?
A.
Unsaturated fatty acids pack less closely and have lower melting points.
B.
Cellulose chains prevent crystallization of the oil.
C.
Saturated fatty acids form straight chains with lower melting points.
D.
Glycosidic bonds hydrolyse at room temperature.
Question 21
A lipid has four fused carbon rings and is mostly non-polar. What type of molecule is it?
A.
Disaccharide
B.
Wax
C.
Phospholipid
D.
Steroid
Question 22
Why can testosterone pass through a phospholipid bilayer more readily than a charged ion?
A.
It is mostly non-polar and can enter the hydrophobic bilayer interior.
B.
It forms glycosidic bonds with membrane proteins.
C.
It is a polysaccharide that is hydrolysed at the membrane.
D.
It has many charged phosphate groups.
Question 23
A phospholipid bilayer has a thickness of 8 nm. What is this thickness in metres?
A.
8 × 10³ m
B.
8 × 10⁻⁶ m
C.
8 × 10⁻³ m
D.
8 × 10⁻⁹ m
Question 24
State the storage polysaccharide in plants.
[1]
State the storage polysaccharide in animals.
[1]
Explain one structural feature that makes these polysaccharides compact stores of glucose.
[1]
Question 25
State the monosaccharide from which cellulose is made.
[1]
Describe the orientation of adjacent monomers in cellulose.
[1]
Explain how cellulose chains provide tensile strength in plant cell walls.
[1]
Question 26
State the small alcohol molecule found in triglycerides and phospholipids.
[1]
Distinguish the composition of a triglyceride from that of a phospholipid.
[1]
State the bond formed between glycerol and a fatty acid.
[1]
Question 27
The diagram shows a simplified phospholipid with a circular head and two tails.
State the term for a molecule that has both hydrophilic and hydrophobic regions.
[1]
Identify which part of a phospholipid is hydrophilic.
[1]
Explain why phospholipids form a bilayer in water.
[1]
Question 28
Define glycoprotein.
[1]
State where the carbohydrate chain of a membrane glycoprotein is usually positioned in an animal cell.
[1]
Explain how ABO antigens can lead to a transfusion reaction.
[1]
Question 29
State the tissue specialized for storing triglycerides in animals.
[1]
Give one reason triglycerides are suitable for long-term energy storage.
[1]
Explain how triglyceride stores can help animals living in cold habitats.
[1]
Question 30
A molecular diagram shows three fused six-membered carbon rings and one fused five-membered carbon ring.
Identify the class of lipid shown.
[1]
Give one example of this class of lipid.
[1]
State one property that allows many molecules in this class to pass through phospholipid bilayers.
[1]
Question 31
State what is meant by a covalent bond.
[1]
Outline two ways carbon atoms can form different molecular skeletons.
[1]
Convert 2.5 µm to metres.
[1]
Question 32
The graph shows the rate at which glucose is released from two storage polysaccharides by the same enzyme preparation.
State which polysaccharide releases glucose faster at the start of the experiment.
[1]
Compare the shapes of the two curves.
[1]
Explain how branching could account for the difference in glucose release.
[1]
Question 33
The graph shows subcutaneous adipose tissue thickness and mean heat-loss rate in three mammal species living in different aquatic habitats.
State the habitat associated with the lowest heat-loss rate.
[1]
Describe the relationship between adipose tissue thickness and heat-loss rate.
[1]
Explain how adipose tissue affects heat loss.
[1]
Suggest one disadvantage of a very thick adipose layer in a warm habitat.
[1]
Question 34
Liposomes form when phospholipids are shaken in water. The figure shows their structure.
Identify the region labelled X.
[1]
State whether region Y is hydrophilic or hydrophobic.
[1]
Explain why the liposome has an aqueous interior and exterior separated by a bilayer.
[1]
Question 35
State the effect of C=C bonds on the shape of many naturally occurring unsaturated fatty acid chains.
[1]
Explain how this affects melting point.
[1]
State whether a lipid rich in unsaturated fatty acids is more likely to be an oil or a fat at room temperature.
[1]
Question 36
State one advantage of glycogen over free glucose as an intracellular store.
[1]
Explain why branching in glycogen is useful in animal cells.
[1]
State the reaction by which glucose monomers are removed from glycogen.
[1]
Question 37
State what is meant by oxidation of an organic molecule.
[1]
Explain why glucose is a suitable molecule for short-term transport and energy release.
[1]
Question 38
A food scientist analysed fatty acids in three edible lipids and measured whether each lipid was solid or liquid at 20 °C.
| Sample | Saturated fatty acids / % | Monounsaturated fatty acids / % | Polyunsaturated fatty acids / % | State at 20 °C |
|---|---|---|---|---|
| A | 24 | 51 | 25 | Liquid |
| B | 42 | 49 | 9 | Solid |
| C | 67 | 29 | 4 | Solid |
Identify the sample most likely to be an oil.
[1]
Describe the evidence that supports this identification.
[1]
Evaluate the conclusion that saturation alone determines whether a lipid is solid or liquid.
[1]
Question 39
Red blood cells from four donors were mixed separately with anti-A and anti-B antibodies. Agglutination indicates that the corresponding ABO antigen is present.
| Donor | With anti-A | With anti-B |
|---|---|---|
| 1 | Yes | No |
| 2 | No | Yes |
| 3 | Yes | Yes |
| 4 | No | No |
Identify the donor with blood group AB.
[1]
Identify the donor with blood group O.
[1]
Explain why agglutination occurs only with some antibody mixtures.
[1]
Suggest why a transfusion with incompatible ABO antigens can be dangerous.
[1]
Question 40
The graph shows uptake of three substances by artificial phospholipid vesicles over time: oestradiol, glucose and sodium ions.
Identify the substance with the greatest uptake after the same time interval.
[1]
Compare uptake of glucose and sodium ions.
[1]
Explain the uptake pattern for oestradiol.
[1]
Suggest why sodium ions show the lowest uptake.
[1]
Question 41
The table shows four carbon compounds found in living organisms, with their carbon skeleton type and one physical property.
| Compound | Carbon skeleton | Property at 25 °C |
|---|---|---|
| Palmitic acid | Unbranched chain | Solid |
| Phytanic acid | Branched chain | Liquid |
| Glucose | Single ring | Water-soluble solid |
| Cholesterol | Multiple fused rings | Water-insoluble solid |
Identify the compound with a multiple-ring skeleton.
[1]
Describe one difference between the branched-chain and unbranched-chain compounds shown.
[1]
Suggest why carbon can form all the skeleton types shown.
[1]
Question 42
Outline two properties of glucose that make it useful in organisms.
[1]
Explain why plants and animals store glucose as polysaccharides rather than as large amounts of free glucose.
[1]
Question 43
Describe the arrangement of beta-glucose monomers in cellulose.
[1]
Explain how the structure of cellulose is related to its function in plant cell walls.
[1]
Question 44
Define hydrophilic, hydrophobic and amphipathic.
[1]
Explain how the amphipathic nature of phospholipids causes bilayer formation in water.
[1]
Question 45
Two groups of migratory birds were monitored during a long flight. The graph shows estimated mass of stored glycogen and stored triglyceride over time.
State which store contributes more mass at the start of the flight.
[1]
Describe how the two stores change during the flight.
[1]
Evaluate why triglyceride is the main long-term store used during migration.
[1]
Question 46
Outline how a triglyceride is formed.
[1]
Compare and contrast triglycerides and phospholipids in structure and function.
[1]
Question 47
Distinguish saturated, monounsaturated and polyunsaturated fatty acids.
[1]
Discuss how fatty acid structure affects melting point and the occurrence of oils and fats in energy storage.
[1]
Question 48
Outline two properties of triglycerides that make them suitable for long-term energy storage.
[1]
Evaluate the roles of adipose tissue in animals living in cold and warm habitats.
[1]
Question 49
Describe how steroids can be recognized from molecular diagrams and give one example.
[1]
Explain why non-polar steroids can pass through phospholipid bilayers and why this differs from polar or charged substances.
[1]
Question 50
Outline how condensation and hydrolysis change carbohydrate polymers.
[1]
Compare and contrast carbohydrates and lipids as energy storage compounds in organisms.
[1]
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