ESAT 2025 Biology Esat.fyi Biology
10 questions10 marks20Updated August 2026
The ESAT 2025 Biology Esat.fyi Biology paper in full: all 10 questions, each with its answer. ESAT is the Engineering and Science Admissions Test. Sit it cold under exam timing, mark it, then work back through anything you missed using the solutions below.
Questions and answers are free. Full step-by-step worked solutions unlock with a free account. Start practising.
Question 1
1 markFamilial hypercholesterolaemia in a certain family is caused by a recessive allele of the LDLR gene. A woman and her partner are both unaffected carriers of this allele, and they have a daughter who does not have the condition. Consider the following statements. Statement 1: the LDLR gene is transcribed and its mRNA is translated within the nucleus, and the completed receptor protein is then exported from the cell. Statement 2: because she is unaffected, the probability that the daughter carries the recessive allele is 1/2. Statement 3: if the daughter has children with a man who is not a carrier of the allele, none of their children can have the condition. Which statement(s) is/are correct?
- A.none
- B.1 only
- C.2 only
- D.3 only
- E.1 and 2
- F.1 and 3
- G.2 and 3
- H.1, 2 and 3
Answer: D
Question 2
1 markIn a species of beetle, body colour is controlled by a single gene: allele A (dominant) gives black and allele a gives brown. Two heterozygous black beetles are crossed. Consider these statements. Statement 1: if the AA genotype is lethal before hatching, then among the beetles that do hatch the ratio of black to brown is 2:1. Statement 2: if instead the brown (aa) beetles hatch normally but are sterile, then no brown beetles occur among the offspring. Statement 3: if there is neither lethality nor sterility, the ratio of black to brown among the offspring is 1:1. Which statement(s) is/are correct?
- A.none
- B.1 only
- C.2 only
- D.3 only
- E.1 and 2
- F.1 and 3
- G.2 and 3
- H.1, 2 and 3
Answer: B
Question 3
1 markA diploid animal produces gametes that each contain a mass m of nuclear DNA. A particular healthy body cell from this animal is measured and found to contain a mass 4m of nuclear DNA. Consider these statements about the cell. Statement 1: it could be a cell that has replicated its DNA and is about to undergo mitosis. Statement 2: it could be a cell that has replicated its DNA and is about to undergo the first division of meiosis. Statement 3: it contains twice as much DNA as a normal body cell of this animal that is not dividing. Which statement(s) is/are correct?
- A.none
- B.1 only
- C.2 only
- D.3 only
- E.1 and 2
- F.1 and 3
- G.2 and 3
- H.1, 2 and 3
Answer: H
Question 4
1 markResearchers investigate protein X in a plant. At equal rates of photosynthesis they compare three lines: the wild type (P), a knockout that lacks protein X (Q), and a rescue line (R) in which the gene for protein X has been reinserted into the knockout. Water-use efficiency is the mass of carbon fixed per unit mass of water transpired, and is inversely related to the transpiration rate. Line Q has a higher water-use efficiency than P, and line R behaves like P. Consider these statements. Statement 1: protein X normally acts to increase the plant's transpiration rate. Statement 2: the results demonstrate that protein X is a channel protein located in the guard-cell membrane. Statement 3: if line Q were grown in more humid air, its water-use efficiency would rise. Which statement(s) is/are correct?
- A.none
- B.1 only
- C.2 only
- D.3 only
- E.1 and 2
- F.1 and 3
- G.2 and 3
- H.1, 2 and 3
Answer: F
Question 5
1 markAn enzyme replicates DNA. Its rate is measured across a range of temperatures for two DNA substrates, one with 100% GC base pairs and one with 40% GC. The temperature coefficient Q10 of the rate is defined as the rate at (T + 10) degrees C divided by the rate at T degrees C. Consider these statements. Statement 1: for the 40% GC substrate, Q10 is greater than 1 at every temperature shown. Statement 2: a Q10 greater than 1 over an interval means the reaction rate increased across that 10 degree interval. Statement 3: above a substrate's optimum temperature, its Q10 for the next 10 degree interval is less than 1. Which statement(s) is/are correct?
- A.none
- B.1 only
- C.2 only
- D.3 only
- E.1 and 2
- F.1 and 3
- G.2 and 3
- H.1, 2 and 3
Answer: G
Question 6
1 markAn in-vitro model reproduces the digestion of protein in the stomach and in the small intestine, with each digestive juice pre-warmed to 37 degrees C. Which row correctly identifies, for both compartments, the principal protein-digesting enzyme and the pH at which it works best?
- A.stomach: pepsin, pH 2; small intestine: trypsin, pH 8
- B.stomach: trypsin, pH 8; small intestine: pepsin, pH 2
- C.stomach: pepsin, pH 8; small intestine: trypsin, pH 2
- D.stomach: amylase, pH 2; small intestine: pepsin, pH 8
- E.stomach: pepsin, pH 2; small intestine: pepsin, pH 8
- F.stomach: trypsin, pH 2; small intestine: trypsin, pH 8
Answer: A
Question 7
1 markThree identical cores of plant tissue are cut and weighed. Core 1 is placed in a sucrose solution of higher water potential than the cells; core 2 in a solution of water potential equal to that of the cells; core 3 in a solution of lower water potential. After 30 minutes the cores are reweighed. Consider these statements. Statement 1: core 1 will have gained mass, because water enters the cells by osmosis down a water-potential gradient. Statement 2: core 3 will have lost mass, and its cells may become plasmolysed if the external solution is concentrated enough. Statement 3: in core 2 there is no movement of water molecules across the cell membranes at all. Which statement(s) is/are correct?
- A.none
- B.1 only
- C.2 only
- D.3 only
- E.1 and 2
- F.1 and 3
- G.2 and 3
- H.1, 2 and 3
Answer: E
Question 8
1 markIn humans, ABO blood group is determined by three alleles: I-A and I-B are codominant with each other, and both are dominant to i. A man of blood group AB has children with a woman of blood group O. Consider these statements. Statement 1: a child of this couple could belong to blood group O. Statement 2: three-quarters of their children are expected to belong to blood group A. Statement 3: a child could belong to blood group AB, like the father. Which statement(s) is/are correct?
- A.none
- B.1 only
- C.2 only
- D.3 only
- E.1 and 2
- F.1 and 3
- G.2 and 3
- H.1, 2 and 3
Answer: A
Question 9
1 markOn four islands of differing age, the number of finch species present was recorded. Island W, the youngest, had 2 species; island X had 4; island Y had 5; and island Z, the oldest, had 4 species. Consider these statements. Statement 1: the data show that an older island always has more finch species than a younger one. Statement 2: island Y has 150% more finch species than island W. Statement 3: because islands X and Z have the same number of species, they must have identical climates and food supplies. Which statement(s) is/are correct?
- A.none
- B.1 only
- C.2 only
- D.3 only
- E.1 and 2
- F.1 and 3
- G.2 and 3
- H.1, 2 and 3
Answer: C
Question 10
1 markA cell maintains an internal potassium-ion concentration many times higher than that of the surrounding fluid. When the cell is treated with a poison that halts ATP production, the internal potassium concentration slowly falls until it equals the external concentration. Consider these statements. Statement 1: building up potassium against its concentration gradient requires active transport, driven by energy from respiration. Statement 2: after the poison takes effect, potassium leaves the cell by diffusion down its concentration gradient. Statement 3: the poison must act by denaturing the phospholipids of the cell-surface membrane. Which statement(s) is/are correct?
- A.none
- B.1 only
- C.2 only
- D.3 only
- E.1 and 2
- F.1 and 3
- G.2 and 3
- H.1, 2 and 3
Answer: E