IB DP Biology Mock Exam HL Paper 1B Set 4 - 2025 Syllabus
IB DP Biology Mock Exam HL Paper 1B Set 4
Prepare for the IB DP Biology Exam with our comprehensive IB DP Biology Exam Mock Exam HL Paper 1B Set 4. Test your knowledge and understanding of key concepts with challenging questions covering all essential topics. Identify areas for improvement and boost your confidence for the real exam
Question
▶️ Answer/Explanation
(a)
At 2 minutes: • 35S ≈ 80% outside the cells • 32P ≈ 32% outside the cells
Difference: \[ 80\% – 32\% = \boxed{48\%} \] (Accept values 46–50%.)
(b)
• Phosphorus (P) is found in DNA, while sulphur (S) is found in proteins.
• Only a small percentage of radioactive 32P remains outside the cells, meaning the labelled DNA entered the bacteria.
• A large percentage of 35S stays outside the cells, showing viral proteins did not enter.
• Since the material that enters the cell is the material that directs viral replication, this demonstrates that DNA—not protein—is the genetic material.
(c)(i)
A correctly labelled DNA nucleotide must include:
• A pentose sugar (deoxyribose), drawn as a five-sided ring and labelled
• A nitrogenous base attached to carbon 1′ of deoxyribose
• A phosphate group attached to carbon 5′ of deoxyribose
(c)(ii)
Purines: Adenine (A), Guanine (G)
Pyrimidines: Thymine (T), Cytosine (C)
(All four bases must be correctly listed.)