Free Biological molecules questions for AS Level Biology (9700), part of Cells & molecules. Each question has the answer and the marking points an examiner would look for.
Generate a full Biological Molecules worksheet →All Cells & molecules questionsWhich row describes the bonds in these molecules?
| glycogen | cellulose | triglyceride | |
|---|---|---|---|
| A | α-1,4 glycosidic only | β-1,4 glycosidic | ester |
| B | α-1,4 and α-1,6 glycosidic | α-1,4 glycosidic | ester |
| C | α-1,4 and α-1,6 glycosidic | β-1,4 glycosidic | ester |
| D | α-1,4 and α-1,6 glycosidic | β-1,4 glycosidic | peptide |
Answer: C
Which statement describes condensation reaction?
Answer: C
Which row compares collagen and haemoglobin?
| shape | quaternary structure | contains prosthetic group | |
|---|---|---|---|
| A | fibrous / globular | haemoglobin only | both |
| B | fibrous / globular | both have | collagen only |
| C | globular / fibrous | both have | haemoglobin only |
| D | fibrous / globular | both have | haemoglobin only |
Answer: D
The structure of a protein is described at four levels.
Describe the bonds that maintain the tertiary structure of a protein.
Explain how the structure of haemoglobin relates to its function.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | hydrogen, ionic, disulfide, hydrophobic interactions hydrogen bonds B1 ionic bonds B1 disulfide bonds (and hydrophobic interactions) between R groups B1 | 3 |
| (b) | quaternary, four chains with haem; globular soluble four polypeptide chains each with a haem group containing Fe²⁺ to bind O₂ B1 globular and soluble so carried in blood B1 | 2 |
This question is about biological molecules.
Describe how two α-glucose molecules join to form maltose.
Explain how the structure of glycogen makes it suited for energy storage in animal cells.
Explain why collagen is suited to its role in tendons.
Describe a test to show that a solution contains a non-reducing sugar.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | condensation; glycosidic bond between C1 and C4; water removed condensation reaction B1 forming a 1,4-glycosidic bond B1 a molecule of water is removed B1 | 3 |
| (b) | branched, many ends for rapid hydrolysis; compact; insoluble, no osmotic effect highly branched with 1,6 links so many ends for rapid hydrolysis by enzymes B1 compact / coiled so much stored in small space B1 insoluble so does not affect water potential B1 | 3 |
| (c) | three chains in triple helix; H bonds between chains; cross-links between molecules; staggered fibrils high tensile strength Any 3 of: three polypeptides wound into a triple helix held by hydrogen bonds; covalent cross-links between molecules form fibrils; ends staggered so no weak points; high tensile strength B3 | 3 |
| (d) | Benedict’s negative; boil with dilute HCl, neutralise with NaHCO₃; Benedict’s again, red-brown precipitate test with Benedict’s first and get a negative result B1 boil with dilute hydrochloric acid then neutralise with sodium hydrogencarbonate B1 heat with Benedict’s again: orange-red precipitate B1 | 3 |
Starch, glycogen and cellulose are polysaccharides of glucose.
Compare the structures of amylose and cellulose.
Explain how glycogen is suited to energy storage in animals.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | α vs β glucose; helix vs straight chains; H-bonds between chains amylose: α-glucose, 1,4 glycosidic bonds, helix B1 cellulose: β-glucose, alternate molecules inverted B1 straight chains linked by hydrogen bonds into microfibrils B1 | 3 |
| (b) | branched, compact, insoluble, rapid hydrolysis highly branched so many ends for rapid hydrolysis B1 compact and insoluble so no osmotic effect B1 | 2 |
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