IB DP Biology Mock Exam HL Paper 1A Set 2 - 2025 Syllabus

IB DP Biology Mock Exam HL Paper 1A Set 2

Prepare for the IB DP Biology Exam with our comprehensive IB DP Biology Exam Mock Exam HL Paper 1A Set 2. 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

IB DP Biology Mock Tests -All Sets

Question

Which symbol indicates the polarity of the oxygen atom in the water molecule?

(A) δ⁺
(B) δ⁻
(C) +
(D) −

▶️ Answer/Explanation

Oxygen is more electronegative than hydrogen, so it attracts the shared electrons in the covalent bonds more strongly. This gives oxygen a partial negative charge, represented by the symbol δ⁻.
✅ Answer: (B)

Question

Which row correctly matches the level of structure of a protein molecule with the bonds that stabilize it?

Option	Level of Structure	Bonds
A	primary	peptide and hydrogen bonds between amine and carboxyl groups
B	secondary	hydrogen bonds between R-groups of amino acids
C	tertiary	disulfide, hydrogen and ionic bonds between R-groups of amino acids
D	quaternary	covalent bonds between hydrophobic and hydrophilic regions on the polypeptide subunits

▶️ Answer/Explanation

The tertiary structure of a protein is stabilized by interactions between the R-groups (side chains) of amino acids. These include disulfide bridges (covalent), hydrogen bonds, ionic interactions, and hydrophobic forces, which give the protein its three-dimensional conformation.
✅ Answer: (C)

Question

What occurs during the stages of respiration?

Option	Stage of respiration	Decarboxylation	Reduced NAD produced
A	Glycolysis	No	No
B	Link reaction	Yes	No
C	Krebs cycle	Yes	Yes
D	Electron transport chain	No	Yes

▶️ Answer/Explanation

The Krebs cycle (citric acid cycle) includes decarboxylation steps that release CO₂ and produces multiple reduced electron carriers (including NADH).
✅ Answer: (C)

IB DP Biology Mock Exam HL Paper 1A Set 2 - 2025 Syllabus