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Question 1
Carbon atoms are able to form a wide diversity of biological molecules. What property of carbon is most directly responsible for this diversity?
A.
A carbon atom dissolves readily in aqueous solvents.
B.
A carbon atom has a complete outer electron shell when unbonded.
C.
A carbon atom can form up to four covalent bonds with other atoms.
D.
A carbon atom forms only ionic bonds with non-metallic elements.
Question 2
During hydrolysis of a polysaccharide, what happens to the water molecule?
A.
It is released when two monosaccharides form a glycosidic bond.
B.
It is oxidized to release energy for digestion.
C.
It is split, providing and groups to the products.
D.
It forms a peptide bond between adjacent monomers.
Question 3
What property defines lipids as a group in living organisms?
A.
They are all soluble in water because they contain many hydroxyl groups.
B.
They dissolve in non-polar solvents and are only sparingly soluble in aqueous solvents.
C.
They are all polymers made from repeating fatty acid monomers.
D.
They all contain phosphate groups attached to glycerol.
Question 4
Excess glucose is commonly stored as starch in plants or glycogen in animals rather than as free glucose. What is the main advantage of this conversion?
A.
Glucose cannot be oxidized to release energy unless it is part of a polymer.
B.
Polysaccharides contain nitrogen, allowing cells to store amino groups.
C.
Polysaccharides are more soluble than glucose and diffuse rapidly through membranes.
D.
Large polysaccharides have less effect on osmotic concentration than many free glucose molecules.
Question 5
What feature of cellulose contributes most directly to the high tensile strength of plant cell walls?
A.
Compact coils of -glucose stored as insoluble granules in chloroplasts.
B.
Coiled chains of -glucose packed with ester bonds between adjacent chains.
C.
Straight chains of -glucose grouped in bundles and cross-linked by hydrogen bonds.
D.
Highly branched chains of -glucose with many ends for enzyme action.
Question 6
In a phospholipid bilayer surrounded by aqueous solutions on both sides, how are the phospholipids arranged?
A.
Hydrophobic tails face the water and hydrophilic heads point toward the centre of the bilayer.
B.
Hydrophilic heads and hydrophobic tails are randomly oriented throughout the bilayer.
C.
Phosphate heads are removed, leaving only fatty acid tails in contact with water.
D.
Hydrophilic heads face the water and hydrophobic tails point toward the centre of the bilayer.
Question 7
A fatty acid is described as monounsaturated. Which structural diagram is consistent with this description?
A.
B.
C.
D.
Question 8
One glycerol molecule reacts by condensation with two fatty acids and one phosphate-containing group. What molecule is formed and how many water molecules are released?
A.
Triglyceride; three water molecules
B.
Phospholipid; two water molecules
C.
Wax; one water molecule
D.
Phospholipid; three water molecules
Question 9
Oestradiol and testosterone can pass through phospholipid bilayers partly because they are steroids. Which diagram shows the characteristic steroid core?
A.
B.
C.
D.
Question 10
Carbon atoms form the backbone of many biological molecules.
State the maximum number of covalent bonds that one carbon atom can form.
[1]
Outline how the bonding properties of carbon allow the formation of diverse biological molecules.
[2]
0
Question 11
The diagram shows two glucose molecules reacting to form a disaccharide.
State the type of reaction by which the disaccharide is formed.
[1]
State the name of the covalent bond formed between the glucose monomers.
[1]
Explain why water is produced during this reaction.
[2]
0
Question 12
During digestion, carbohydrate polymers are converted into smaller molecules.
Define hydrolysis.
[1]
Outline how hydrolysis of a polysaccharide produces monosaccharides.
[2]
0
Question 13
A student must identify a hexose monosaccharide from ring-form molecular diagrams. Which diagram shows a hexose?
A.
B.
C.
D.
Question 14
Red blood cells display A or B antigens on membrane glycoproteins. What role does the carbohydrate part of these glycoproteins have in blood transfusion compatibility?
A.
It forms the hydrophobic interior of the red blood cell membrane.
B.
It catalyses hydrolysis of plasma proteins during incompatible transfusions.
C.
It acts as a cell-surface recognition marker that may be recognized by the immune system.
D.
It stores glucose for rapid release when red blood cells need energy.
Question 15
Two energy-storage lipids have fatty acid chains of similar length. Lipid X contains a higher proportion of saturated fatty acids than lipid Y. What difference is most likely at ?
A.
Lipid Y is more likely to be solid because it contains fewer single bonds.
B.
Lipid X has a higher melting point and is more likely to be solid.
C.
Lipid X has a lower melting point because its chains contain more bends.
D.
Lipid Y has a higher melting point because double bonds allow closer packing.
Question 16
Glucose is a monosaccharide used in transport and energy metabolism.
State one feature of glucose that makes it suitable for transport in blood plasma.
[1]
Explain why storing large quantities of free glucose in a cell could be harmful.
[2]
State the process by which glucose releases energy in cell respiration.
[1]
0
Question 17
Plants store glucose as starch and animals store glucose as glycogen.
State the monosaccharide monomer used to build both starch and glycogen.
[1]
Explain how the structure of starch or glycogen makes it suitable for energy storage.
[3]
0
Question 18
A person with blood group A receives red blood cells from a donor with blood group B.
State where the carbohydrate chains of membrane glycoproteins are usually found in animal cells.
[1]
Outline the role of ABO glycoproteins in cell-cell recognition.
[2]
Suggest why the transfused donor red blood cells may be attacked by the recipient's immune system.
[1]
0
Question 19
Triglycerides and phospholipids are both formed from glycerol and fatty acid molecules.
State the name of the covalent bond formed between glycerol and a fatty acid.
[1]
Compare the formation of a triglyceride and a phospholipid.
[3]
0
Question 20
A student compared four carbon compounds found in living organisms. The compounds differed in the number of carbon atoms, the presence of double bonds and the overall shape of the carbon skeleton.
| Compound | Carbon atoms | Carbon skeleton | C–C bonds | Atoms bonded to C | Diameter / nm |
|---|---|---|---|---|---|
| A | 4 | unbranched chain | single only | H, O | 0.9 |
| B | 7 | branched chain | single only | H, O | 1.3 |
| C | 18 | unbranched chain | single and double | H, O, N | 2.4 |
| D | 6 | ring structure | single only | H, O | 1.1 |
Identify the compound with the greatest diversity of covalent bonding around carbon atoms.
[1]
Using the data, outline two ways in which carbon atoms allow the formation of diverse biological molecules.
[2]
The diameter of a molecule in the table is given as . Convert this diameter to metres.
[1]
0
Question 21
An investigation followed the formation of a carbohydrate polymer from glucose monomers in a cell extract. The amount of free glucose and the amount of water released were measured over time.
Describe the change in free glucose concentration during the investigation.
[1]
Explain how the graph provides evidence for a condensation reaction.
[2]
State the name of the covalent bond formed between adjacent glucose monomers in the polymer.
[1]
0
Question 22
Cellulose forms strong microfibrils in plant cell walls.
State the glucose monomer from which cellulose is made.
[1]
Explain how the structure of cellulose gives plant cell walls tensile strength.
[3]
0
Question 23
The table summarizes fatty acid composition and physical state for two lipid samples stored at .
| Lipid sample | Saturated fatty acids / % | Unsaturated fatty acids / % | Physical state at 20 °C |
|---|---|---|---|
| Sample A | 30 | 70 | liquid |
| Sample B | 70 | 30 | solid |
Distinguish between saturated and polyunsaturated fatty acids.
[2]
Explain why the sample with a higher proportion of unsaturated fatty acids is more likely to be liquid at .
[2]
0
Question 24
Marine mammals living in cold water often have a thick layer of subcutaneous adipose tissue.
State the main lipid stored in adipose tissue.
[1]
Explain how adipose tissue helps marine mammals maintain body temperature in cold water.
[2]
Suggest one reason why triglycerides are suitable for long-term energy storage.
[1]
0
Question 25
Phospholipids are mixed with water and spontaneously form bilayers.
Define amphipathic.
[1]
Explain why phospholipids form a bilayer in water.
[3]
0
Question 26
A digestive enzyme was added to a suspension of starch at . Samples were taken at intervals and tested for starch and reducing sugar.
| Time / min | Starch colour intensity / a.u. | Reducing sugar concentration / mmol dm^-3 |
|---|---|---|
| 0 | 5 | 0.0 |
| 5 | 4 | 0.7 |
| 10 | 3 | 1.5 |
| 15 | 2 | 2.3 |
| 20 | 1 | 3.1 |
| 25 | 0 | 3.8 |
| 30 | 0 | 3.8 |
Identify the product whose concentration increases during the experiment.
[1]
Explain why water is required for the digestion of the starch polymer.
[2]
Suggest why the reducing sugar concentration stops increasing near the end of the experiment.
[1]
0
Question 27
Molecular diagrams of four monosaccharides were analysed together with measurements of their movement through an aqueous solution.
Identify one hexose from the molecular diagrams.
[1]
Outline how a pentose can be distinguished from a hexose in the diagrams.
[1]
Using the data, explain why glucose can be transported in blood plasma.
[2]
Suggest why cells usually store excess glucose as a polysaccharide rather than as many free glucose molecules.
[1]
0
Question 28
Samples of starch from a plant tissue and glycogen from an animal tissue were treated with an enzyme that removes glucose from chain ends. The molecular structures and rates of glucose release were compared.
| Polysaccharide | Non-reducing chain ends per equal mass / relative units | Glucose release rate / μmol min^-1 |
|---|---|---|
| Starch | 4 | 1.2 |
| Glycogen | 12 | 3.6 |
State which polysaccharide releases glucose at the higher rate in the experiment.
[1]
Using the structural information, explain the difference in glucose release rate.
[2]
Explain why both starch and glycogen are suitable for compact energy storage.
[2]
0
Question 29
Red blood cells from four donors were tested with antibodies against A and B antigens. The antigen structures are glycoproteins with different terminal carbohydrate groups exposed at the cell surface.
| Donor | anti-A antibody | anti-B antibody |
|---|---|---|
| A | Agglutination | No agglutination |
| B | No agglutination | Agglutination |
| C | Agglutination | Agglutination |
| D | No agglutination | No agglutination |
Identify the donor whose red blood cells carry both A and B antigens.
[1]
Explain how the glycoproteins shown in the stimulus allow cell-cell recognition.
[2]
Suggest why transfusing red blood cells with unfamiliar A or B antigens may be harmful.
[1]
0
Question 30
Four biological substances were shaken separately with water and with a non-polar solvent. The mixtures were left to settle before observations were recorded.
| Substance | In water | In non-polar solvent |
|---|---|---|
| A | insoluble | soluble |
| B | soluble | insoluble |
| C | insoluble | insoluble |
| D | sparingly soluble | insoluble |
Identify one substance that is most likely to be a lipid.
[1]
Explain why the solubility results are evidence that the identified substance is hydrophobic.
[2]
Evaluate whether the test can distinguish between all classes of lipid shown in the stimulus.
[2]
0
Question 31
The diagram shows the structure of a hormone molecule that can pass through the phospholipid bilayer of a cell membrane.
Identify the class of lipid shown by the four fused carbon rings.
[1]
State one example of a steroid hormone.
[1]
Explain why steroid hormones can pass through a phospholipid bilayer more readily than charged molecules.
[2]
0
Question 32
Cellulose fibres from plant cell walls were examined at increasing levels of magnification. The arrangement of glucose monomers, cellulose chains and microfibrils was recorded.
Describe the orientation of adjacent glucose monomers in the cellulose chain.
[1]
Explain how the arrangement of cellulose chains produces high tensile strength.
[3]
Suggest how cellulose microfibrils help plant cells resist bursting when water enters by osmosis.
[1]
0
Question 33
A model was used to compare the formation of two lipids from glycerol, fatty acids and a phosphate-containing group. The number of water molecules released was recorded for each product.
State the number of fatty acid molecules linked to glycerol in a triglyceride.
[1]
Using the stimulus, distinguish between a triglyceride and a phospholipid.
[2]
Explain why three water molecules are released when one triglyceride forms.
[2]
0
Question 34
Fatty acids extracted from a seed oil and from the adipose tissue of an endothermic mammal were analysed. The number of carbon-carbon double bonds and melting points of the fatty acids were recorded.
Identify the fatty acid class represented by molecules with more than one carbon-carbon double bond.
[1]
Describe the relationship between number of carbon-carbon double bonds and melting point shown in the graph.
[2]
Explain why the seed oil sample remains liquid at ordinary room temperature more often than the mammal fat sample.
[2]
0
Question 35
The diagram shows three carbon-based molecules found in living organisms. Molecule X is an unbranched chain, molecule Y is a branched chain and molecule Z contains fused rings.
Use the diagram to explain why carbon can form a diversity of stable biological molecules.
I.
Identify two features of carbon bonding shown in the molecules.
[2]
II.
State how a covalent bond holds atoms together in these molecules.
[1]
Explain how differences in the carbon skeletons of X, Y and Z could lead to different biological functions.
[3]
0
Question 36
A student models the formation and digestion of biological polymers using beads to represent monomers and clips to represent covalent bonds.
Compare condensation and hydrolysis reactions in the context of carbohydrate polymers.
I.
Explain how monosaccharides are joined to form a polysaccharide.
[2]
II.
Explain how digestion of a polysaccharide produces monomers.
[2]
Discuss why organisms use both condensation and hydrolysis reactions in metabolism.
[3]
0
Question 37
The diagram shows molecules involved in the formation of two lipid types, P and Q.
Compare the formation of lipid P and lipid Q.
I.
Identify the bond formed between glycerol and fatty acids, and describe how it forms.
[2]
II.
Distinguish the composition of lipid P from lipid Q.
[2]
Explain why lipid Q can contribute to membrane formation whereas lipid P cannot form a bilayer in the same way.
[3]
0
Question 38
A hospital blood bank tests red blood cells from four donors. The surface glycoproteins on the cells differ in the terminal carbohydrate groups that form ABO antigens.
Explain how carbohydrate chains on glycoproteins allow recognition of red blood cells.
I.
Describe the structure and position of membrane glycoproteins involved in recognition.
[2]
II.
State what is meant by an antigen in this context.
[1]
Discuss why ABO antigens are important when selecting blood for transfusion.
[3]
0
Question 39
Researchers compared three mammal species living in habitats with different water temperatures. They measured the thickness of subcutaneous adipose tissue, resting metabolic rate and rate of heat loss from the body surface.
| Species | Habitat water temp / °C | Subcutaneous adipose thickness / mm | Resting metabolic rate / W kg^-1 | Heat loss / W m^-2 |
|---|---|---|---|---|
| Species A | 25 | 5 | 4.7 | 55 |
| Species B | 15 | 15 | 5.8 | 32 |
| Species C | 4 | 30 | 7.0 | 16 |
Describe the relationship between adipose tissue thickness and rate of heat loss.
[1]
Explain why triglycerides in adipose tissue are suitable for thermal insulation in these mammals.
[2]
Discuss one advantage and one disadvantage of storing large amounts of triglyceride in adipose tissue for an animal in a cold habitat.
[2]
0
Question 40
Artificial vesicles were made from phospholipids in water. A second experiment compared the movement of two signalling molecules, oestradiol and a charged peptide, across the vesicle membrane.
Using the diagram, state why phospholipids are described as amphipathic.
[1]
Explain how the amphipathic nature of phospholipids leads to bilayer formation in water.
[2]
Evaluate the conclusion that molecular polarity is important in determining movement across the phospholipid bilayer.
[2]
0
Question 41
The figure shows two ring-form monosaccharides, A and B, and a storage polysaccharide made from repeated glucose units.
Use the figure to relate monosaccharide form to function.
I.
Distinguish between a pentose and a hexose using the ring diagrams.
[1]
II.
Explain why glucose is suitable for transport and use as a respiratory substrate.
[2]
Explain why cells commonly store excess glucose as starch or glycogen rather than as free glucose.
[2]
Discuss how branching affects the mobilization of glucose from animal glycogen stores.
[3]
0
Question 42
Plant cell walls contain cellulose microfibrils. Red blood cell membranes contain glycoproteins that include ABO antigens.
Explain how the structure of cellulose is related to its function in plant cell walls.
I.
Describe the arrangement of glucose monomers in cellulose chains.
[2]
II.
Explain how cellulose microfibrils give strength to plant cell walls.
[3]
Explain the role of glycoproteins in cell-cell recognition, using ABO antigens as an example.
[3]
0
Question 43
A food manufacturer compares two lipid mixtures for use in spreads. Mixture A contains a high proportion of saturated fatty acids. Mixture B contains a high proportion of unsaturated fatty acids.
Use fatty acid structure to explain expected differences between the two lipid mixtures.
I.
Distinguish saturated, monounsaturated and polyunsaturated fatty acids.
[3]
II.
Explain how unsaturation affects melting point.
[2]
Evaluate whether mixture A or mixture B would be more similar to plant oils used for energy storage.
[3]
0
Question 44
Researchers compared adipose tissue thickness and habitat temperature in three mammal species. They also measured the proportion of body energy stored as triglyceride and as glycogen.
| Species | Habitat temperature / °C | Adipose tissue thickness / mm | Energy stored as triglyceride / % | Energy stored as glycogen / % |
|---|---|---|---|---|
| Weddell seal | 0 | 45 | 94 | 2 |
| Red deer | 15 | 16 | 89 | 4 |
| Dromedary camel | 35 | 6 | 91 | 3 |
Analyse the relationship between adipose tissue and habitat shown in the data.
I.
Describe the trend between habitat temperature and adipose tissue thickness.
[2]
II.
Explain why triglycerides in adipose tissue are suitable for thermal insulation.
[2]
Evaluate the use of triglycerides rather than glycogen for long-term energy storage in these mammals.
[4]
0
Question 45
The figure shows a phospholipid bilayer separating an extracellular solution from the cytoplasm. Two small hormone molecules, oestradiol and molecule R, are shown outside the cell. Oestradiol has a steroid structure; molecule R is charged.
Explain how phospholipid structure causes bilayer formation.
I.
Describe the amphipathic nature of a phospholipid.
[2]
II.
Explain the arrangement of phospholipids in water.
[2]
Discuss why oestradiol can pass through the bilayer more readily than charged molecule R.
[3]
0
Question 46
The diagram compares three glucose polymers: polymer A is coiled, polymer B is highly branched and polymer C consists of straight parallel chains with cross-links between chains.
Use the diagram to distinguish storage and structural polysaccharides.
I.
Identify which polymers are most likely to be starch, glycogen and cellulose, giving one reason for each identification.
[2]
II.
Explain why coiling and branching are useful in energy storage polysaccharides.
[2]
Explain why polymer C is better suited to resisting stretching than storing rapidly mobilized glucose.
[3]
0
Question 47
Two organisms are preparing for a period with limited food availability. Organism X increases glycogen stores in liver and muscle. Organism Y increases triglyceride stores in adipose tissue.
Compare the molecular properties of glycogen and triglycerides as energy stores.
I.
Explain how glycogen structure allows rapid mobilization of glucose.
[2]
II.
Explain why triglycerides are suited to dense long-term storage.
[2]
Discuss how synthesis of these storage compounds can contribute to carbon sinks in living systems.
[4]
0
Question 48
The table shows the fatty acid composition and melting behaviour of lipids extracted from seeds of two plant species and from adipose tissue of an endothermic mammal.
| Lipid extract | Saturated fatty acids / % | Unsaturated fatty acids / % | Melting point / °C | State at 25 °C |
|---|---|---|---|---|
| Plant seed oil A | 15 | 85 | -12 | liquid |
| Plant seed oil B | 27 | 73 | 6 | liquid |
| Mammal adipose tissue | 53 | 47 | 39 | solid |
Analyse how fatty acid composition explains the melting behaviour in the table.
I.
Describe the relationship between degree of unsaturation and melting behaviour shown by the extracts.
[2]
II.
Explain the molecular basis of this relationship.
[2]
Evaluate the claim that the data support a form-function relationship in plant oils and endotherm fats.
[4]
0
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