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Exam Review

Key Facts: HKDSE Biology Exam

HKDSE Biology is set and administered by the Hong Kong Examinations and Assessment Authority (HKEAA).

Paper 1 lasts 2 hours 30 minutes and is worth 120 marks, including 36 multiple-choice questions in Section A.

Paper 2 lasts 1 hour and is worth 40 marks, with four 20-mark elective sections of which candidates answer two.

School-Based Assessment (SBA) contributes 20% of the final HKDSE Biology subject mark.

Results are graded Level 5** (highest), 5*, 5, 4, 3, 2, 1, with U for unclassified.

The four elective options are Human Physiology, Applied Ecology, Microorganisms and Humans, and Biotechnology.

In the 2024 HKDSE, 15,578 candidates sat Biology and about 8% achieved Level 5 or above.

For the 2026 HKDSE, school candidates pay HK$519 per non-language subject such as Biology.

HKDSE Biology is assessed by Paper 1 (2.5 hrs, 120 marks, 36 MCQs plus written questions) and Paper 2 (1 hr, 40 marks, two of four elective sections), with SBA worth 20%, graded from Level 5** to 1.

Sample HKDSE Biology Practice Questions

Try these sample questions to review concepts for the HKDSE Biology exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Which property of water makes it an effective transport medium and solvent in living organisms?
A.It is a polar molecule that forms hydrogen bonds and dissolves ionic and polar substances
B.Its molecules are non-polar
C.It has a very low specific heat capacity
D.It cannot dissolve mineral ions
Explanation: Water is a polar molecule: the oxygen end is slightly negative and the hydrogen ends slightly positive, so it forms hydrogen bonds and readily dissolves ionic and polar (hydrophilic) solutes. This makes it the main transport medium in blood and xylem sap.
2A student performs Benedict's test on a food sample and the solution turns brick-red after heating. What does this indicate?
A.Presence of starch
B.Presence of protein
C.Presence of reducing sugar
D.Presence of lipid
Explanation: Benedict's solution, when heated with a reducing sugar such as glucose, is reduced to form a brick-red precipitate of copper(I) oxide. A blue colour means no reducing sugar is present.
3Which statement correctly describes the basic structural unit (monomer) of proteins?
A.Amino acids joined by peptide bonds
B.Glucose
C.Fatty acids and glycerol
D.Nucleotides
Explanation: Proteins are polymers of amino acids linked by peptide bonds formed in condensation reactions. There are about 20 different amino acids, and their sequence determines the protein's structure and function.
4According to the fluid mosaic model, the cell membrane is mainly composed of:
A.A single layer of protein only
B.A continuous sheet of cholesterol
C.A cellulose cell wall
D.A phospholipid bilayer with embedded proteins
Explanation: The fluid mosaic model describes the membrane as a phospholipid bilayer in which proteins are embedded (intrinsic) or attached to the surface (extrinsic). The hydrophilic phosphate heads face outward and the hydrophobic fatty acid tails face inward, while components move laterally, giving fluidity.
5A plant cell is placed in a concentrated salt solution. What is most likely to happen to the cell?
A.It bursts (lyses)
B.It becomes turgid
C.It undergoes plasmolysis as water leaves by osmosis
D.Its cell wall dissolves
Explanation: In a hypertonic (more concentrated) solution, water moves out of the cell by osmosis down the water potential gradient. The cell membrane pulls away from the cell wall, a condition called plasmolysis.
6Which process requires energy (ATP) to move substances across the cell membrane against a concentration gradient?
A.Simple diffusion
B.Osmosis
C.Facilitated diffusion
D.Active transport
Explanation: Active transport moves substances from a region of lower concentration to higher concentration (against the gradient) using carrier proteins and energy from ATP. An example is the uptake of mineral ions by root hair cells.
7Which organelle is the site of aerobic respiration in eukaryotic cells?
A.Chloroplast
B.Mitochondrion
C.Ribosome
D.Golgi apparatus
Explanation: The mitochondrion is the site of aerobic respiration. Its inner membrane is folded into cristae to increase surface area for the electron transport chain, and the Krebs cycle occurs in the matrix, producing most of the cell's ATP.
8Enzymes speed up biochemical reactions by:
A.Lowering the activation energy of the reaction
B.Increasing the activation energy required
C.Being permanently used up in the reaction
D.Raising the temperature of the cell
Explanation: Enzymes are biological catalysts that lower the activation energy needed for a reaction, allowing it to proceed faster at body temperature. They are not used up and can be reused many times.
9The lock-and-key hypothesis of enzyme action states that:
A.Any substrate can fit into any enzyme
B.Enzymes change the products of every reaction
C.The active site has a specific shape complementary to its substrate
D.Enzymes work only at 100 degrees Celsius
Explanation: In the lock-and-key hypothesis, the enzyme's active site has a specific shape that is complementary to the shape of its substrate, so each enzyme catalyses only one type of reaction. This explains enzyme specificity.
10When the temperature rises well above an enzyme's optimum, the rate of reaction falls sharply because:
A.The substrate freezes
B.The pH automatically becomes neutral
C.More enzyme is produced
D.The enzyme is denatured as its active site changes shape
Explanation: High temperatures break the hydrogen and other bonds maintaining the enzyme's tertiary structure, so the active site changes shape and the substrate can no longer bind. This irreversible loss of function is called denaturation.

About the HKDSE Biology Exam

HKDSE Biology is an elective science subject in the Hong Kong Diploma of Secondary Education, set and administered by the HKEAA. It is assessed through Paper 1 (the compulsory part, 2.5 hours, 120 marks, with a 36-question multiple-choice Section A plus short, structured and essay questions) and Paper 2 (electives, 1 hour, 40 marks, four sections of which candidates answer two). The compulsory curriculum spans Cells and Molecules of Life, Genetics and Evolution, Organisms and Environment, and Health and Diseases, while the four elective options are Human Physiology, Applied Ecology, Microorganisms and Humans, and Biotechnology. A School-Based Assessment component, based on practical and field work in S5 and S6, contributes 20% of the final subject mark. In the 2024 HKDSE there were 15,578 Biology candidates, with Human Physiology the most popular elective.

Exam sponsor: Hong Kong Examinations and Assessment Authority (HKEAA). The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Questions

100 questions

Time Limit

Paper 1: 2 hours 30 minutes; Paper 2: 1 hour

Passing Score

Graded Level 5** down to Level 1, with U for unclassified; no fixed pass mark, Level 3 is a common benchmark.

Exam / Certification Fees

HK$519 per subject for 2026 school candidates (private Permanent HKIC holders pay HK$519 plus a HK$595 initial fee).

Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

23%

Cells and Molecules of Life

Molecules of life, cell structure and membranes, transport, enzymes, photosynthesis and respiration.

18%

Genetics and Evolution

DNA and molecular genetics, inheritance, variation, evolution, and molecular biology techniques.

33%

Organisms and Environment

Gas exchange, transport, nutrition, coordination, homeostasis, reproduction, and ecosystems and human impact.

8%

Health and Diseases

Personal health, infectious and non-infectious diseases, and body defence and immunity.

18%

Elective Topics

Human Physiology, Applied Ecology, Microorganisms and Humans, and Biotechnology (any two studied).

Preparing for the HKDSE Biology Exam

What You Need to Know

  • Passing score: Graded Level 5** down to Level 1, with U for unclassified; no fixed pass mark, Level 3 is a common benchmark.
  • Exam length: 100 questions
  • Time limit: Paper 1: 2 hours 30 minutes; Paper 2: 1 hour
  • Exam / certification fees: HK$519 per subject for 2026 school candidates (private Permanent HKIC holders pay HK$519 plus a HK$595 initial fee). Official sources

Using Our Practice Resources

  • Work through all 100 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

HKDSE Biology: Suggested Study Strategy

1Master the compulsory part thoroughly, especially Organisms and Environment, which carries the largest share of marks.
2Practise the 36 Paper 1 multiple-choice questions under time pressure (about 1 to 1.5 minutes each) to build speed and accuracy.
3Use precise biological terminology; HKEAA examiner reports note that vague or mismatched vocabulary loses marks.
4Choose your two electives early and learn the named processes (for example osmoregulation, the nephron, fermentation and recombinant DNA technology) in depth.
5Practise data-interpretation and scientific-investigation questions, as Paper 1 includes experimental and graph-based items.
6Link concepts across topics (for example enzymes with digestion, or DNA with biotechnology), because the exam rewards cross-topic integration.

Frequently Asked Questions

Who sets and administers HKDSE Biology?

It is set and administered by the Hong Kong Examinations and Assessment Authority (HKEAA), the official public examinations body for the Hong Kong Diploma of Secondary Education.

How is HKDSE Biology assessed?

Through Paper 1 (the compulsory part, 2.5 hours, 120 marks, including 36 multiple-choice questions plus short, structured and essay questions) and Paper 2 (electives, 1 hour, 40 marks). A School-Based Assessment based on practical work contributes 20% of the subject mark.

What elective topics are available in HKDSE Biology?

There are four elective options: Human Physiology: Regulation and Control, Applied Ecology, Microorganisms and Humans, and Biotechnology. Candidates study any two of the four and answer two of the four sections in Paper 2.

How is HKDSE Biology graded?

Results are reported on a scale of Level 5** (highest), 5*, 5, 4, 3, 2, 1, with U for unclassified. There is no fixed pass mark, though Level 3 is often used as a benchmark for university and further study.

How much does it cost to take HKDSE Biology in 2026?

For the 2026 HKDSE, school candidates pay HK$519 per non-language subject. Private candidates holding a Permanent Hong Kong Identity Card pay HK$519 per subject plus a HK$595 initial fee.