Biology Paper One – 2025 – Practice Questions with Model Answers – Secondary School, Exams of Nursing

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• BIOLOGY PAPER ONE.

"Describe how we breathe in. [3 marks] - CORRECT ANSWER 1. Diaphragm (muscle) contracts pulling diaphragm down;

2. External intercostal muscles contract pulling/moving ribs upwards/outwards;
3. (Causes) volume increase and pressure decrease in thoracic cavity;" "Use your understanding of osmosis to explain why the air pressure in the tube increased. [3 marks] - CORRECT ANSWER 1. Molasses/solution has a lower water potential
4. Water moves in (across) partially/selectively permeable bladder;
5. Increased (molasses/solution) volume" "Describe the appearance and behaviour of chromosomes during prophase and during anaphase of mitosis. [4 marks] - CORRECT ANSWER (In prophase)
6. Chromosomes/chromatids (continue to) condense;
7. Chromosomes attach to spindle (fibres) (In anaphase)
8. Centromeres divide/split;
9. Chromosomes/chromatids moved/pulled to opposite poles/sides/ends;" "r = -0.98 (P < 0.05) What can you conclude from this result? [2 marks] - CORRECT ANSWER 1. Strong/significant negative (correlation);
10. (Because probability of) correlation occurring by chance is less than / < 0.05 / 5%
11. Reject null hypothesis;" "Give three structural differences between an mRNA molecule and a tRNA molecule. [3 marks] - CORRECT ANSWER mRNA
12. (Has) codon(s)
13. No hydrogen/H bonds
14. Linear/straight/not folded
15. Long/many nucleotides/bases tRNA
16. (Has) anticodon;
17. Has hydrogen/H bonds
18. 'Clover (leaf' shape)/

"Suggest one change the scientists could make to both frog populations to increase the number of mating calls. [1 mark] - CORRECT ANSWER Add (sexually active) female(s);" "Suggest and explain the effect EE2 pollution in frog habitats will have on frog breeding. [4 marks] - CORRECT ANSWER (Effect on breeding)

1. Less mating/breeding OR Fewer offspring; (Explanation)
2. Fewer advertisement calls, so females not attracted
3. Fewer mating calls as males less (sexually) active." "Describe and explain how you would use cell fractionation and ultracentrifugation to obtain a sample of nuclei from muscle tissue. [6 marks] - CORRECT ANSWER 1. Homogenise (tissue) to break open cells
4. Filter to remove cells debris;
5. Cold (solution) to prevent enzyme activity;
6. keep solution isotonic to prevent organelles bursting
7. Buffered (solution) to stop enzymes/protein denaturing;
8. Centrifuge/spin at low(er) speed so nuclei in pellet" "Describe the role of organelles in the production and release of enzymes by animal cells. Do not include details of transcription in your answer. [5 marks] - CORRECT ANSWER 1. DNA in nucleus codes for enzyme/protein (production);
9. Ribosomes produce enzyme/protein
10. Rough endoplasmic reticulum transports/modifies enzymes
11. Mitochondria produce ATP;
12. Golgi apparatus modify/process/ package/transport enzymes/protein
13. Vesicles move (protein) to cell(-surface) membrane" "Describe the structure of ATP. Outline how named enzymes break down and resynthesise ATP. [4 marks] - CORRECT ANSWER 1. Ribose, Adenine and 3 phosphates;
14. ATP to ADP + Pi by ATP hydrolase in hydrolysis (reaction);
15. ADP + Pi to ATP by ATP synthase;
16. (In) condensation (reaction);"

" The ratio of saturated to unsaturated fatty acids in a cell-surface membrane determines the extent of the membrane's fluidity. Suggest and explain why there was more phagocytosis. [3 marks] - CORRECT ANSWER 1. More unsaturated fatty acids increases fluidity (in (cell-surface membrane);

2. (Making cell-surface) membrane more fluid/ flexible;
3. Easy to engulf;" "Describe the processes of facilitated diffusion and active transport. [3 marks] - CORRECT ANSWER 2. (Facilitated diffusion) movement down a concentration gradient via carrier/channel protein;
4. (Active transport) movement against a concentration gradient via carrier protein using ATP;" "What are microvilli? [1 mark] - CORRECT ANSWER (Highly) folded cell(-surface) membrane;" "Vitamin A is a fat-soluble substance. Micelles are involved in the process of vitamin A absorption. Describe the process of vitamin A absorption into cells lining the ileum. [3 marks] - CORRECT ANSWER 1. Combine/mix/join with bile salts;
5. Make (more) soluble (in water);
6. Diffuses (into cells/ileum);"