DSE Practice Test — 50 Questions Across All Subjects

This practice test covers 10 questions from each of Biology, Chemistry, Physics, Mathematics, and Economics — the five highest-enrolment DSE subjects. Each question is modelled on the style and difficulty of real DSE papers. Work through all 50 questions under timed conditions before checking the answer key.

• Time limit: 75 minutes (90 seconds per question)
• Format: Multiple choice — select the best answer from options A–D
• Marking: 1 mark per question, 50 marks total
• Conditions: Attempt without notes. Record your answers on a separate sheet.
• After the test: Check the answer key at the bottom. Study the explanations for any questions you got wrong.

Which organelle is responsible for protein synthesis in eukaryotic cells?

Correct: B (index 1)

Ribosomes are the sites of protein synthesis. They can be free in the cytoplasm or attached to the rough endoplasmic reticulum. Mitochondria carry out aerobic respiration, the Golgi apparatus modifies and packages proteins, and lysosomes contain digestive enzymes.

easy — 1 mark

An enzyme-catalysed reaction reaches its maximum rate ($V_{max}$) when:

Correct: B (index 1)

At $V_{max}$, all enzyme active sites are saturated with substrate. Increasing substrate concentration further cannot increase the rate because there are no free active sites. This is described by the Michaelis-Menten model.

easy — 1 mark

In a monohybrid cross between two heterozygous parents (Aa × Aa), what is the expected phenotypic ratio of the offspring?

Correct: C (index 2)

For a monohybrid cross with complete dominance, Aa × Aa produces AA:Aa:aa in the ratio 1:2:1. Since AA and Aa both show the dominant phenotype, the phenotypic ratio is 3 (dominant) : 1 (recessive).

easy — 1 mark

Which of the following is an example of a density-dependent limiting factor?

Correct: C (index 2)

Density-dependent factors have a greater effect as population density increases. Disease spreads more rapidly in crowded populations. Natural disasters such as fires, droughts, and floods are density-independent — they affect populations regardless of density.

medium — 1 mark

The structure responsible for gas exchange in the lungs is the:

Correct: B (index 1)

Alveoli are the tiny air sacs where gas exchange occurs. Their thin walls (one cell thick) and large surface area (approximately 70 m²) enable efficient diffusion of oxygen and carbon dioxide. The bronchus and trachea conduct air; the diaphragm is a muscle used in breathing.

easy — 1 mark

During photolysis in photosynthesis, water molecules are split to produce:

Correct: B (index 1)

Photolysis occurs in the light-dependent reactions of photosynthesis. Water is split by light energy into oxygen (released as a waste product), hydrogen ions (H⁺), and electrons. The hydrogen ions and electrons are used to reduce NADP⁺.

medium — 1 mark

Which type of white blood cell produces antibodies?

Correct: C (index 2)

B lymphocytes (B cells) differentiate into plasma cells that produce antibodies. T lymphocytes coordinate the immune response and kill infected cells directly. Neutrophils and macrophages are phagocytes that engulf pathogens.

easy — 1 mark

During DNA replication, the enzyme that joins Okazaki fragments on the lagging strand is:

Correct: C (index 2)

DNA ligase joins Okazaki fragments by catalysing the formation of phosphodiester bonds between adjacent fragments. Helicase unwinds the double helix, DNA polymerase III adds nucleotides to the growing strand, and primase synthesises RNA primers.

medium — 1 mark

In a negative feedback loop regulating blood glucose, an increase in blood glucose concentration triggers the release of:

Correct: C (index 2)

When blood glucose rises, beta cells in the pancreas secrete insulin. Insulin promotes the uptake of glucose by cells and the conversion of glucose to glycogen in the liver, reducing blood glucose levels back to normal.

easy — 1 mark

Natural selection favours alleles that:

Correct: B (index 1)

Natural selection favours traits that increase an organism’s fitness — its ability to survive and reproduce. Alleles that enhance reproductive success become more frequent in the population over generations, regardless of whether they are initially common or rare.

medium — 1 mark

How many protons, neutrons, and electrons are in the ion ${}^{31}_{15}\text{P}^{3-}$?

Correct: B (index 1)

Protons = atomic number = 15. Neutrons = mass number − atomic number = 31 − 15 = 16. Electrons = protons − charge = 15 − (−3) = 18 (gaining 3 electrons gives the 3− charge).

easy — 1 mark

Which type of bonding is present in sodium chloride (NaCl)?

Correct: B (index 1)

NaCl is formed by the transfer of an electron from sodium to chlorine, creating Na⁺ and Cl⁻ ions. The electrostatic attraction between these oppositely charged ions constitutes ionic bonding. Covalent bonding involves sharing electrons; metallic bonding involves a sea of delocalised electrons.

easy — 1 mark

The enthalpy change for the reaction $\text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2$ is $+178 \text{ kJ mol}^{-1}$. This reaction is:

Correct: B (index 1)

A positive enthalpy change means the reaction is endothermic. The product (CaO + CO₂) has higher enthalpy than the reactant, so the products are thermodynamically less stable than the reactant. The reaction is non-spontaneous at standard conditions.

medium — 1 mark

Which factor does NOT affect the rate of a chemical reaction?

Correct: D (index 3)

The equilibrium constant ($K_{eq}$) describes the position of equilibrium, not the rate of reaction. Temperature, concentration, catalysts, and surface area all affect the rate by changing how frequently particles collide with sufficient energy.

medium — 1 mark

For the equilibrium $\text{N}_2\text{O}_4(g) \rightleftharpoons 2\text{NO}_2(g)$, increasing the pressure will:

Correct: B (index 1)

Le Chatelier’s principle states the system will oppose the change. Increasing pressure favours the side with fewer moles of gas. The left side has 1 mole of gas; the right side has 2 moles. Equilibrium shifts to the left to reduce pressure. $K_{eq}$ only changes with temperature.

medium — 1 mark

A solution has a pH of 3. What is the hydrogen ion concentration?

Correct: B (index 1)

$\text{pH} = -\log[\text{H}^+]$, so $[\text{H}^+] = 10^{-\text{pH}} = 10^{-3} = 1 \times 10^{-3} \text{ mol dm}^{-3}$.

easy — 1 mark

In the reaction $\text{Zn} + \text{Cu}^{2+} \rightarrow \text{Zn}^{2+} + \text{Cu}$, zinc is:

Correct: C (index 2)

Zinc loses 2 electrons (Zn → Zn²⁺ + 2e⁻), so it is oxidised. By losing electrons, zinc reduces Cu²⁺ to Cu, so zinc is the reducing agent. Remember: OIL RIG — Oxidation Is Loss, Reduction Is Gain (of electrons).

medium — 1 mark

Which functional group is present in ethanol?

Correct: B (index 1)

Ethanol (CH₃CH₂OH) contains a hydroxyl group (−OH), making it an alcohol. A carboxyl group is found in carboxylic acids, a carbonyl group in aldehydes and ketones, and an amino group in amines.

easy — 1 mark

In an electrolytic cell, reduction occurs at the:

Correct: B (index 1)

In both galvanic and electrolytic cells, reduction always occurs at the cathode and oxidation at the anode. A useful mnemonic: Red Cat (reduction at cathode), An Ox (anode oxidation).

easy — 1 mark

What mass of NaOH (Mr = 40) is needed to neutralise 50 cm³ of 0.2 mol dm⁻³ HCl?

Correct: A (index 0)

The balanced equation is $\text{NaOH} + \text{HCl} \rightarrow \text{NaCl} + \text{H}_2\text{O}$, so the mole ratio is 1:1.

Moles of HCl = $0.2 \times 0.050 = 0.01 \text{ mol}$.

Moles of NaOH needed = 0.01 mol.

Mass of NaOH = $0.01 \times 40 = 0.4 \text{ g}$.

medium — 1 mark

A car accelerates uniformly from rest to 20 m/s in 10 seconds. What is its acceleration?

Correct: B (index 1)

$a = \frac{v - u}{t} = \frac{20 - 0}{10} = 2 \text{ m/s}^2$.

easy — 1 mark

A 5 kg box is pushed across a frictionless surface with a force of 20 N. What is the acceleration of the box?

Correct: A (index 0)

Using Newton’s second law: $F = ma$, so $a = \frac{F}{m} = \frac{20}{5} = 4 \text{ m/s}^2$.

easy — 1 mark

A 2 kg ball is dropped from a height of 10 m. What is its kinetic energy just before it hits the ground? (Take $g = 10 \text{ m/s}^2$)

Correct: B (index 1)

By conservation of energy, the potential energy lost equals the kinetic energy gained: $KE = mgh = 2 \times 10 \times 10 = 200 \text{ J}$.

easy — 1 mark

A wave has a frequency of 50 Hz and a wavelength of 3 m. What is its speed?

Correct: A (index 0)

$v = f\lambda = 50 \times 3 = 150 \text{ m/s}$.

easy — 1 mark

A 12 V battery is connected to a resistor of 6 Ω. What current flows through the circuit?

Correct: C (index 2)

Using Ohm’s law: $I = \frac{V}{R} = \frac{12}{6} = 2 \text{ A}$.

easy — 1 mark

The magnetic field around a straight current-carrying wire forms:

Correct: B (index 1)

By the right-hand grip rule, the magnetic field lines around a straight current-carrying wire form concentric circles in a plane perpendicular to the wire. The field strength decreases with distance from the wire.

easy — 1 mark

The internal energy of an ideal gas depends on:

Correct: A (index 0)

For an ideal gas, the internal energy depends only on temperature. This is because ideal gas molecules have no intermolecular forces, so potential energy is zero. The internal energy is entirely kinetic, which is proportional to temperature.

medium — 1 mark

In nuclear fission, a heavy nucleus splits into lighter nuclei. The mass of the products is:

Correct: C (index 2)

In fission, some mass is converted to energy according to $E = mc^2$. The total mass of the products is less than the mass of the original nucleus. This “mass defect” accounts for the energy released in the reaction.

medium — 1 mark

A car of mass 1000 kg travels around a circular track of radius 50 m at a constant speed of 20 m/s. What is the centripetal force acting on the car?

Correct: B (index 1)

$F = \frac{mv^2}{r} = \frac{1000 \times 20^2}{50} = \frac{1000 \times 400}{50} = \frac{400{,}000}{50} = 8{,}000 \text{ N}$.

medium — 1 mark

Two objects of masses $m$ and $4m$ are separated by a distance $r$. If the gravitational force between them is $F$, what is the force when the distance is reduced to $r/2$?

Correct: C (index 2)

By Newton’s law of gravitation, $F = \frac{Gm_1 m_2}{r^2}$. If $r$ is halved, $r^2$ becomes $r^2/4$, so the force increases by a factor of 4: $F' = 4F$.

medium — 1 mark

Solve $3x + 7 = 22$.

Correct: B (index 1)

$3x = 22 - 7 = 15$, so $x = 15 \div 3 = 5$.

easy — 1 mark

What are the roots of $x^2 - 7x + 12 = 0$?

Correct: C (index 2)

$(x - 3)(x - 4) = 0$, so $x = 3$ or $x = 4$.

easy — 1 mark

If $f(x) = 2x^2 - 3x + 1$, what is $f(-2)$?

Correct: A (index 0)

$f(-2) = 2(-2)^2 - 3(-2) + 1 = 2(4) + 6 + 1 = 8 + 6 + 1 = 15$.

easy — 1 mark

What is the gradient of the line passing through $(2, 5)$ and $(6, 13)$?

Correct: A (index 0)

Gradient $m = \frac{13 - 5}{6 - 2} = \frac{8}{4} = 2$.

easy — 1 mark

A bag contains 4 red, 3 blue, and 2 green marbles. One marble is drawn at random. What is the probability it is NOT blue?

Correct: B (index 1)

Total marbles = 9. Non-blue marbles = 4 + 2 = 6. $P(\text{not blue}) = \frac{6}{9} = \frac{2}{3}$.

easy — 1 mark

In a right-angled triangle, the side opposite angle $\theta$ is 5 and the hypotenuse is 13. What is $\cos \theta$?

Correct: B (index 1)

The adjacent side = $\sqrt{13^2 - 5^2} = \sqrt{169 - 25} = \sqrt{144} = 12$. Therefore $\cos \theta = \frac{\text{adjacent}}{\text{hypotenuse}} = \frac{12}{13}$.

medium — 1 mark

What is the 10th term of the arithmetic sequence 3, 7, 11, 15, …?

Correct: A (index 0)

Common difference $d = 4$. $T_n = a + (n-1)d = 3 + 9 \times 4 = 3 + 36 = 39$.

medium — 1 mark

If $A = \begin{pmatrix} 2 & 1 \\ 3 & 4 \end{pmatrix}$, what is the determinant of $A$?

Correct: A (index 0)

$\det(A) = (2)(4) - (1)(3) = 8 - 3 = 5$.

easy — 1 mark

Solve $\log_2 x = 5$.

Correct: C (index 2)

$\log_2 x = 5$ means $2^5 = x$, so $x = 32$.

easy — 1 mark

How many ways can 5 books be arranged on a shelf?

Correct: C (index 2)

The number of arrangements = $5! = 5 \times 4 \times 3 \times 2 \times 1 = 120$.

easy — 1 mark

Opportunity cost is defined as:

Correct: B (index 1)

Opportunity cost is the value of the next best alternative given up when making a choice. It is a fundamental concept in economics because scarcity forces trade-offs. It is not always measured in monetary terms.

easy — 1 mark

If the price of a good increases and the quantity demanded decreases, this illustrates:

Correct: B (index 1)

The law of demand states that, ceteris paribus, as price increases, quantity demanded decreases. This inverse relationship is shown by the downward-sloping demand curve.

easy — 1 mark

A good has a price elasticity of demand (PED) of −2.5. This means:

Correct: B (index 1)

$|\text{PED}| > 1$ indicates elastic demand. A PED of −2.5 means a 1% increase in price causes a 2.5% decrease in quantity demanded. The negative sign reflects the inverse relationship between price and quantity demanded.

medium — 1 mark

In perfect competition, firms are:

Correct: B (index 1)

In perfect competition, there are many small firms selling identical products. No single firm can influence the market price — they are price takers. In the long run, firms earn only normal profits due to free entry and exit.

medium — 1 mark

A negative externality exists when:

Correct: B (index 1)

A negative externality is a cost imposed on a third party not involved in the production or consumption of a good. Pollution is a classic example — the factory produces goods, consumers buy them, but nearby residents bear the cost of pollution.

medium — 1 mark

Gross Domestic Product (GDP) measures:

Correct: B (index 1)

GDP is the total market value of all final goods and services produced within a country’s borders in a given time period. It measures economic output, not wealth, exports alone, or income distribution.

easy — 1 mark

Expansionary fiscal policy involves:

Correct: B (index 1)

Expansionary fiscal policy aims to stimulate aggregate demand by cutting taxes (increasing disposable income) and increasing government spending (directly increasing demand). Options C and D describe contractionary monetary policy.

easy — 1 mark

A country has a comparative advantage in producing a good if:

Correct: B (index 1)

Comparative advantage means having a lower opportunity cost in producing a good compared to another country. A country can have an absolute advantage (produce more with the same resources) in all goods but still benefit from trade through comparative advantage.

medium — 1 mark

The money multiplier effect describes:

Correct: B (index 1)

When banks receive deposits, they keep a fraction as reserves and lend out the rest. The lent money is re-deposited and lent again, creating a multiplier effect on the original deposit. The money multiplier = 1 / reserve ratio.

medium — 1 mark

Which of the following is a supply-side policy?

Correct: B (index 1)

Supply-side policies aim to increase the productive capacity of the economy. Reducing income tax increases the incentive to work, shifting the long-run aggregate supply curve to the right. Options A is demand-side; C is monetary policy; D is trade protection.

medium — 1 mark

• Biology — Detailed notes on cell biology, genetics, ecology, and human physiology
• Chemistry — Atomic structure, bonding, energetics, and organic chemistry
• Physics — Mechanics, waves, electricity, and nuclear physics
• Mathematics — Functions, algebra, coordinate geometry, and probability
• Economics — Microeconomics, macroeconomics, and international trade

1. Time yourself strictly. 75 minutes for 50 questions mirrors the pace of real DSE papers.
2. Don’t guess randomly. Eliminate wrong answers before choosing — this builds exam technique.
3. Study the explanations. The explanations for wrong answers teach you more than the right answers do.
4. Retake after revision. Wait one week, then attempt the test again to check retention.
5. Focus on weak areas. Use the diagnostic quizzes on this site to identify and strengthen your weakest topics.

Last updated: 24 July 2026

Written by Wyatt. For questions or feedback, visit wyattau.com.