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ESAT Mock Biology ESAT-BIO-MOCK-1

27 questions27 marks40Updated July 2026

The ESAT Mock Biology ESAT-BIO-MOCK-1 paper in full: all 27 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.

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Question 1

1 mark

A student identifies the following features in a particular cell: a nucleus, mitochondria, and a cell membrane. However, the cell does not possess a cell wall.

Which of the following could be the identity of this cell?

A.a bacterium
B.a human cheek cell
C.a root hair cell
D.a leaf mesophyll cell
E.a fungal cell

Answer: B

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Question 2

1 mark

Which of the following is a correct description of the function of the specified sub-cellular component?

A.The nucleus is the primary site of aerobic respiration within the cell.
B.The cell wall controls the movement of substances into and out of the cell.
C.The chloroplast is the site of protein synthesis in plant cells.
D.The vacuole contains cell sap and helps to maintain the cell's internal pressure.
E.The cytoplasm provides a rigid external structure to support the cell.

Answer: D

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Question 3

1 mark

Which of the following sub-cellular structures are found in both a typical human liver cell and a typical leaf mesophyll cell?

1. cell membrane
2. cytoplasm
3. cell wall
4. mitochondria
5. nucleus

A.1 and 2 only
B.1, 2 and 5 only
C.1, 2, 4 and 5 only
D.1, 2, 3 and 5 only
E.1, 2, 3, 4 and 5

Answer: C

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Question 4

1 mark

Which of the following statements correctly describe(s) the sub-cellular components of a typical prokaryotic cell?

1. The cell membrane contains enzymes responsible for the final stages of aerobic respiration.
2. The chromosomal DNA is enclosed within a double-membrane-bound nucleus to prevent damage from cytoplasmic reactions.
3. Plasmid DNA consists of small, circular loops that can carry accessory genes such as those for antibiotic resistance.
4. The cell wall is a rigid external layer primarily composed of cellulose.

A.1 only
B.3 only
C.1 and 3 only
D.1, 2 and 3 only
E.1, 3 and 4 only

Answer: C

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Question 5

1 mark

A cell is examined under a microscope and found to possess the following features:
- a cell wall
- DNA
- no mitochondria

Which of the following statements about this cell could be correct?

1. The cell is a bacterium and its chromosomal DNA is located in the cytoplasm.
2. The cell is a mature plant cell.
3. The genetic material is organized into a single circular chromosome.
4. The cell contains plasmid DNA.

A.1 only
B.1 and 2 only
C.1 and 3 only
D.1, 3 and 4 only
E.1, 2, 3 and 4

Answer: D

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Question 6

1 mark

A student lists four structures found in the human body:

1. The lining of the small intestine
2. A white blood cell
3. The liver
4. The respiratory system

What is the correct order of these structures, starting from the simplest level of organisation to the most complex?

A.1, 2, 3, 4
B.2, 1, 3, 4
C.2, 3, 1, 4
D.3, 2, 1, 4
E.4, 3, 1, 2

Answer: B

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Question 7

1 mark

Which of the following descriptions accurately matches a human structure to its level of organisation?

A.Red blood cell: a tissue found within the circulatory system.
B.Pancreas: an organ that produces digestive enzymes and hormones.
C.Muscle fibre: a tissue that enables the movement of limbs.
D.Large intestine: an organ system involved in water absorption.
E.Brain: a tissue that coordinates nervous impulses.

Answer: B

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Question 8

1 mark

A student investigated the change in mass of potato tissue in different sucrose solutions. Three identical potato cylinders, each with an initial mass of

10.0\text{ g}

, were placed in three different sucrose solutions (X, Y, and Z) for 60 minutes. The cylinders were then removed, blotted dry, and reweighed. The final masses were recorded as:

- Solution X:

10.0\text{ g}

- Solution Y:

11.5\text{ g}

- Solution Z:

8.5\text{ g}

Which of the following statements is correct?

A.Solution X has a higher water potential than the potato cells.
B.Solution Y has a higher water potential than the potato cells.
C.Solution Z has a higher water potential than the potato cells.
D.The concentration of sugar in solution Z is lower than the concentration of sugar in the potato cells.
E.The change in mass in solution Y was caused by the active transport of water into the cells.

Answer: B

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Question 9

1 mark

A cell from a marine organism maintains an internal sodium ion (

Na^+

) concentration of

15\text{ mmol dm}^{-3}

, despite living in seawater where the sodium ion concentration is

450\text{ mmol dm}^{-3}

.

Which of the following processes is directly responsible for maintaining this concentration difference?

A.Sodium ions moving out of the cell by diffusion.
B.Sodium ions moving into the cell by active transport.
C.Sodium ions being pumped out of the cell using energy from respiration.
D.Water moving out of the cell by osmosis to balance the sodium concentration.
E.Sodium ions moving into the cell by diffusion until an equilibrium of $232.5\text{ mmol dm}^{-3}$ is reached.

Answer: C

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Question 10

1 mark

The table below shows some characteristics of three types of movement across cell membranes.

| row | process | direction of net movement | energy required from respiration |
| :--- | :--- | :--- | :--- |
| 1 | diffusion | down a concentration gradient | no |
| 2 | osmosis | from low to high water potential | no |
| 3 | active transport | against a concentration gradient | yes |
| 4 | diffusion | against a concentration gradient | yes |
| 5 | active transport | down a concentration gradient | no |

Which row(s) correctly describe the characteristics of the named process?

A.1 only
B.1 and 3 only
C.2 and 3 only
D.3 and 5 only
E.1, 2, and 3

Answer: B

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Question 11

1 mark

A population of 2000 cells in a tissue culture is studied. It is found that 200 cells are in mitosis, and 800 cells are in the

S

phase of the cell cycle. All other cells are in either the

G1

or

G2

phase. The total duration of one full cell cycle is 20 hours.

Consider the following statements:
1. The

S

phase of the cell cycle for these cells lasts 8 hours.
2. The combined duration of the

G1

and

G2

phases is 10 hours.
3. A cell in the

G2

phase contains twice as many chromosomes as a cell in the

G1

phase.

Which of the statements is/are correct?

A.none of them
B.1 only
C.2 only
D.1 and 2 only
E.1, 2 and 3

Answer: D

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Question 12

1 mark

In a certain species of insect, sex is determined by the

XO

system. Females are

XX

(

2n = 12

) and males are

XO

(

2n = 11

).

A male insect cell undergoes mitosis to produce two daughter cells. During this specific division, a nondisjunction event occurs where the sister chromatids of the

X

chromosome fail to separate and both move to the same pole. All other chromosomes separate and migrate normally to opposite poles.

Which of the following correctly describes the chromosome count and sex chromosome composition of the two resulting daughter cells?

A.Cell 1: 11 ( $X$ ); Cell 2: 11 ( $X$ )
B.Cell 1: 12 ( $XX$ ); Cell 2: 10 ( $O$ )
C.Cell 1: 12 ( $X$ ); Cell 2: 10 ( $X$ )
D.Cell 1: 13 ( $XX$ ); Cell 2: 9 ( $O$ )
E.Cell 1: 11 ( $XX$ ); Cell 2: 11 ( $O$ )

Answer: B

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Question 13

1 mark

In a particular species of beetle, the diploid number of chromosomes is

2n = 20

. A single diploid cell in this beetle undergoes the complete process of meiosis to produce gametes.

Which of the following identifies the number of daughter cells produced and the number of chromosomes in each daughter cell?

A.Daughter cells: $2$ ; chromosomes per cell: $20$
B.Daughter cells: $4$ ; chromosomes per cell: $10$
C.Daughter cells: $4$ ; chromosomes per cell: $20$
D.Daughter cells: $2$ ; chromosomes per cell: $10$
E.Daughter cells: $8$ ; chromosomes per cell: $10$

Answer: B

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Question 14

1 mark

The meiotic cell cycle consists of interphase followed by meiosis. Which of the following statements correctly describes the events of interphase that occur before the first division of meiosis?

A.The cell grows in size and the DNA is replicated.
B.The cell undergoes two successive divisions without DNA replication.
C.The DNA content is halved to prepare for the production of haploid cells.
D.Chromosomes are distributed into four daughter cells.
E.Homologous chromosomes pair up and then immediately separate.

Answer: A

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Question 15

1 mark

Human somatic cells are diploid, containing

46

chromosomes. Which of the following is a correct description of the role of meiosis and fertilisation in the human life cycle?

A.Meiosis produces four genetically identical cells to ensure trait stability.
B.Fertilisation involves two diploid cells fusing to form a tetraploid zygote with $92$ chromosomes.
C.Meiosis produces haploid gametes with $23$ chromosomes so that fertilisation results in a diploid zygote with $46$ chromosomes.
D.Meiosis produces two haploid gametes that each contain $46$ chromosomes.
E.Fertilisation is the process that reduces the chromosome number to ensure the offspring is haploid.

Answer: C

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Question 16

1 mark

An organism reproduces asexually through binary fission. Which of the following statements about its offspring is/are correct?

1. In the absence of mutation, the offspring are genetically identical to the parent.
2. The offspring are produced via the fusion of two haploid gametes.
3. The offspring will always have the same phenotype as the parent, regardless of environmental conditions.

A.1 only
B.2 only
C.1 and 2 only
D.1 and 3 only
E.1, 2 and 3

Answer: A

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Question 17

1 mark

A student is comparing the mechanisms of inheritance in sexual and asexual reproduction. Which of the following statements is/are correct?

1. In sexual reproduction, offspring inherit

100\%

of their nuclear DNA from a single parent.
2. Asexual reproduction results in offspring with exactly the same combination of alleles as the parent, excluding mutations.
3. Genetic variation observed in the offspring of sexual reproduction is solely the result of new mutations.

A.1 only
B.2 only
C.1 and 2 only
D.2 and 3 only
E.1, 2 and 3

Answer: B

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Question 18

1 mark

A population of

100

protozoa reproduces asexually, with each individual dividing into two exactly once every

4

hours. Simultaneously, a population of

100

insects reproduces sexually. In the insect population, each pair produces

4

offspring every

4

hours, after which the parents die. Assume an equal sex ratio in every insect generation.

Which of the following statements is/are correct?

1. At

t = 8\,\text{hours}

, the protozoa population is

400

.
2. At

t = 8\,\text{hours}

, the insect population is

800

.
3. Sexual reproduction in the insect population generates more genetic variation than the asexual reproduction in the protozoa population.

A.1 only
B.2 only
C.1 and 2 only
D.1 and 3 only
E.1, 2 and 3

Answer: D

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Question 19

1 mark

Which of the following statements concerning human chromosomes is/are correct for a healthy individual?

1. A skin cell contains

44

autosomes.
2. A sperm cell contains

22

autosomes.
3. A mature red blood cell contains

22

pairs of autosomes.

A.1 only
B.2 only
C.1 and 2 only
D.1 and 3 only
E.1, 2 and 3

Answer: C

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Question 20

1 mark

Which of the following statements about human phenotypes is/are correct?

1. Most phenotypic characteristics are the result of the interaction of multiple genes.
2. Characteristics determined by a single gene typically show continuous variation across a population.
3. Human height is an example of a characteristic typically controlled by multiple genes.

A.1 only
B.3 only
C.1 and 2 only
D.1 and 3 only
E.1, 2 and 3

Answer: D

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Question 21

1 mark

In a particular species of plant, the allele for red flowers (

R

) is dominant over the allele for white flowers (

r

). A researcher performs a cross between a heterozygous red-flowered plant and a white-flowered plant.

If

400

offspring are produced from this cross, what is the expected number of plants with white flowers?

A.0
B.100
C.200
D.300
E.400

Answer: C

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Question 22

1 mark

A population of

200

plants is studied for a single gene with two alleles,

B

and

b

. The distribution of genotypes in the population is as follows:
-

30\%

are homozygous dominant (

BB

)
-

50\%

are heterozygous (

Bb

)
-

20\%

are homozygous recessive (

bb

)

What is the total number of recessive alleles (

b

) present in this population of

200

plants?

A.40
B.100
C.140
D.180
E.200

Answer: D

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Question 23

1 mark

A human sperm cell is compared to a human liver cell from the same healthy individual. Which of the following statements is/are correct?

1 The sperm cell contains

23

pairs of chromosomes.
2 The liver cell contains the full genome of the individual.
3 The sperm cell and the liver cell contain the same mass of DNA.

A.1 only
B.2 only
C.3 only
D.1 and 2 only
E.2 and 3 only

Answer: B

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Question 24

1 mark

A functional protein consists of a single polypeptide chain of

240

amino acids. Which of the following statements is/are correct?

1. The coding region of the gene for this protein contains at least

720

nucleotide bases.
2. The specific three-dimensional shape of this protein is determined by the sequence of its amino acids.
3. If the

100

th amino acid is changed from leucine to valine, the three-dimensional shape of the protein will definitely be destroyed.

A.1 only
B.2 only
C.1 and 2 only
D.2 and 3 only
E.1, 2 and 3

Answer: C

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Question 25

1 mark

A template strand of DNA has the nucleotide sequence shown below:

3' \text{- TAC CCG TTT GGC -} 5'

Which of the following is correct?

A.The mRNA sequence produced from this template is $3' \text{- AUG GGC AAA CCG -} 5'$ .
B.The sequence of the coding (non-template) DNA strand is $5' \text{- ATG GGC AAA CCG -} 3'$ .
C.There are a total of $12$ codons in the mRNA produced from this sequence.
D.A substitution mutation in the first base of the second triplet is less likely to change the amino acid than a substitution in the third base of that triplet.
E.This sequence of DNA bases contains the code for $12$ different amino acids.

Answer: B

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Question 26

1 mark

A scientist is studying the effects of three different mutations in a gene that codes for a digestive enzyme in a population of organisms. The mutations are described below:

1. A single base substitution in the DNA sequence that results in the same amino acid being incorporated into the protein.
2. A single base substitution that occurs in a non-coding region (intron) of the gene.
3. A single base insertion at the very beginning of the coding sequence of the gene.

Which of the following statements is/are correct?

1. Mutation 1 is considered a mutation because it changes the sequence of nucleotides in the DNA.
2. Mutations 1 and 2 are more likely to have no effect on the phenotype than Mutation 3.
3. Mutation 3 is an example of a mutation that is likely to determine the phenotype of the organism.

A.1 only
B.1 and 2 only
C.1 and 3 only
D.2 and 3 only
E.1, 2 and 3

Answer: E

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Question 27

1 mark

The following DNA sequence represents a segment of the coding strand of a gene:

\text{5'-GTC GCT AAA TAG-3'}

A mutation occurs where the cytosine (

C

) at the 5th position is deleted. The table below shows mRNA codons and the amino acids they code for.

| mRNA Codon | Amino Acid |
| :--- | :--- |
|

\text{GUC}

| Valine |
|

\text{GCU}

| Alanine |
|

\text{GUA}

| Valine |
|

\text{AAA}

| Lysine |
|

\text{AAU}

| Asparagine |
|

\text{UAG}

| STOP |
|

\text{UAA}

| STOP |

Which of the following statements is/are correct?

1. The deletion of the 5th nucleotide changes the sequence of nucleotides in the DNA.
2. A substitution of the 12th nucleotide (guanine,

G

) for an adenine (

A

) would be expected to have no effect on the phenotype.
3. The deletion mutation results in a stop codon being reached earlier in the sequence than in the original gene.

A.1 only
B.2 only
C.1 and 2 only
D.2 and 3 only
E.1, 2 and 3

Answer: C

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