(a) (i) Fig. 6.1 is a diagram of a bacterial cell.
Complete Fig. 6.1 by using the words in the list to label these structures on the answer lines provided.
- cell membrane
- cell wall
- circular DNA
- cytoplasm
- ribosome
(ii) State the names of two structures in the cell in Fig. 6.1 that are not found in animal cells.
(iii) Describe the function of plasmids in bacterial cells.
(b) Many sewage treatment plants use bacteria in the process of cleaning sewage. Some of these bacteria release methane as a waste product. This methane can be burned as a source of energy for the sewage treatment plant. Explain why the production and use of methane in this way is described as sustainable.
(c) Sometimes untreated sewage enters water ecosystems. Describe the effects of untreated sewage on river ecosystems.
▶️ Answer/Explanation
Ans:
(a)(i) The labeled bacterial cell structures are:
(a)(ii) Two structures not found in animal cells: cell wall and circular DNA (or plasmids).
(a)(iii) Plasmids store extra genetic material and enable gene transfer between bacteria, aiding adaptation (e.g., antibiotic resistance).
(b) Methane production is sustainable because it is continuously generated by bacteria during sewage treatment and serves as a renewable energy source when burned.
(c) Untreated sewage depletes oxygen, kills aquatic life, spreads diseases, and disrupts food chains, reducing biodiversity.
Final Answers:
(a)(i) See labeled diagram above.
(a)(ii) Cell wall, circular DNA/plasmids.
(a)(iii) Gene storage/transfer.
(b) Renewable and continuously produced.
(c) Oxygen depletion, biodiversity loss, disease spread.
(a) Fig. 1.1 is a photograph showing different stages of bread‑making. Bread dough is made by mixing flour, water and yeast together. Bread dough A has just been mixed. Bread dough B was mixed a few hours before the photograph was taken and has increased in volume.
(i) State the name of the gas that caused bread dough B to increase in volume.
(ii) State the name of the process in yeast that produces the gas during bread‑making.
(b) State one other product that is made using yeast, apart from food or drink.
(c) Bacteria are another type of microorganism that is used in biotechnology.
Tick two boxes to show why bacteria are useful in biotechnology.
(d) Bacteria and yeast are living organisms. Table 1.1 shows descriptions of some characteristics of living organisms.
Complete Table 1.1 by writing the name for each characteristic described.
(e) State two cell structures that are found in both bacteria and plants.
▶️ Answer/Explanation
Ans:
(a)(i) Carbon dioxide is the gas produced by yeast during fermentation, causing the dough to rise.
(a)(ii) The process is respiration (anaerobic), where yeast converts sugars into CO2 and alcohol.
(b) Yeast is used to produce biofuels (e.g., ethanol) through fermentation.
(c) Bacteria are useful because they make complex molecules (e.g., insulin) and have a rapid reproduction rate.
(d) The characteristics are:
– Sensitivity (responding to stimuli),
– Excretion (removing waste),
– Growth (increase in size/mass).
(e) Common structures in bacteria and plants:
– Cell wall (provides support),
– Cell membrane (controls substance movement).