VCE Biology: the exam, Units 3 and 4, and practice questions with answers

Each daily paper has 8 original questions worth 25 to 35 marks. The Year 12 Biology paper fits Unit 3 and 4 in its photosynthesis, respiration, gene expression, gene technology, allele frequency and evolution questions; skip homeostasis, the kidney, nerves and muscle contraction. The Year 11 Biology paper fits in its immune system, protein synthesis, enzyme and classification questions; its cell, membrane, gas exchange and transport questions are Unit 1 review.

The VCE Biology exam

The approved materials are pens, pencils, highlighters, erasers, sharpeners and rulers: no calculator and no notes. Every outcome in Units 3 and 4 can be examined, along with the key science skills. That is the VCAA's exam specification for the study design from 2022. In 2026 the exam ran on Monday 2 November, 9:00 to 11:45 am, and results come out on Thursday 10 December.

VCE Biology Units 3 and 4

School-assessed Coursework is worth 20% of the study score in Unit 3 and 30% in Unit 4, which includes the investigation. The VCAA moderates SAC marks against your school group's exam results, keeping your rank in the group.

VCE Biology practice questions with answers

We wrote these for this page. Do them without a calculator, as in the exam.

1. The trp operon. Explain what happens to the trp operon in E. coli when tryptophan is plentiful. Answer: tryptophan binds to the repressor protein and changes its shape so it can bind the operator. RNA polymerase is then blocked, so the structural genes for making tryptophan are not transcribed. The cell saves energy by not making what it already has.

2. Enzyme inhibitors. How does a competitive inhibitor differ from a non-competitive one, and which can be overcome by adding more substrate? Answer: a competitive inhibitor has a shape like the substrate and occupies the active site; a non-competitive inhibitor binds elsewhere and changes the active site's shape. Only competitive inhibition is overcome by more substrate, which outcompetes the inhibitor for the active site.

3. Cellular respiration. Give the location, main input and main output of glycolysis and of the electron transport chain. Answer: glycolysis happens in the cytosol: glucose in, 2 pyruvate out, with a small yield of ATP and loaded NADH. The electron transport chain sits on the inner mitochondrial membrane (the cristae): loaded coenzymes and oxygen in, water and most of the cell's ATP out. Without oxygen, cells fall back on fermentation.

4. Gel electrophoresis. A 5000 bp plasmid is cut by a restriction enzyme at two sites 1200 bp apart. What bands appear on the gel, and which travels further? Answer: two fragments: 1200 bp and 3800 bp. DNA is negatively charged and moves toward the positive electrode, and the 1200 bp fragment travels further because smaller fragments move through the gel more easily.

5. Allele frequencies. In a population of 500 plants, 180 are AA, 240 are Aa and 80 are aa. Find the frequency of allele a. Answer: there are 1000 alleles in total. Allele a appears 2 × 80 + 240 = 400 times, so its frequency is 0.40, and A is 0.60. A bushfire that kills plants at random could shift these frequencies by chance alone: a bottleneck, one kind of genetic drift. The Hardy-Weinberg Calculator works with allele and genotype frequencies.

New alleles come from mutation. Name the type of mutation in our Genetics and DNA course, then press Mark.

6. Immunity. Compare the immunity from a vaccine with the immunity a baby gets from antibodies in breast milk. Answer: a vaccine gives artificial active immunity: the body makes its own antibodies and memory cells, so protection lasts. Antibodies in breast milk give natural passive immunity: they work at once, but no memory cells form, so the protection is short-lived.

Use the daily papers as a VCE Biology trial

1. Sit today's Year 12 Biology paper to the suggested time, 35 to 45 minutes, without a calculator.
2. Skip the homeostasis, kidney, nervous system and muscle contraction questions.
3. For Unit 4 immunity, sit the immune system questions on the Year 11 Biology paper.
4. Mark both, sort each lost mark by area of study, and use VCAA past exams for the 40 multiple-choice questions and full timing.

Common VCE Biology mistakes

• Saying the repressor is made only when tryptophan is present. It is always made; tryptophan switches it on.
• Putting the Krebs cycle and electron transport chain in the same place. Krebs is in the matrix; the chain is on the inner membrane.
• Saying bigger DNA fragments travel further. Smaller fragments travel further through the gel.
• Calling breast-milk antibodies active immunity. The baby didn't make them, so it is passive.
• Thinking individuals evolve. Populations change: evolution is a change in allele frequencies in a gene pool.

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