A Unity and Diversity

A1.1 Water

A1.2 Nucleic acids

A2.1 Origins of cells

A2.2 Cell structure

A2.3 Viruses [HL only]

A3.1 Diversity of organisms

A3.2 Classification and cladistics [HL only]

A4.1 Evolution and speciation

A4.2 Conservation of biodiversity

B Form and Function

B1.1 Carbohydrates and lipids

B1.2 Proteins

B2.1 Membranes and membrane transport

B2.2 Organelles and compartmentalization

B2.3 Cell specialization

B3.1 Gas exchange

B3.2 Transport

B3.3 Muscle and motility [HL only]

B4.1 Adaptation to environment

B4.2 Ecological niches

C Interaction and Interdependence

C1.1 Enzymes and metabolism

C1.2 Cell respiration

C1.3 Photosynthesis

C1.3.1—Light energy → chemical energy

C1.3.2—CO₂ → glucose

C1.3.3—Oxygen as by-product

C1.3.4—Photosynthetic pigment separation

C1.3.5—Absorption of specific wavelengths

C1.3.6—Absorption vs. action spectra

C1.3.7—Limiting factors investigation

C1.3.8—CO₂ enrichment experiments

C1.3.9 (HL)—Photosystems

C1.3.10 (HL)—Advantages of pigment arrays

C1.3.11 (HL)—Photolysis of water

C1.3.12 (HL)—ATP production in thylakoids

C1.3.13 (HL)—NADP reduction

C1.3.14 (HL)—Thylakoids as light-dependent systems

C1.3.15 (HL)—Carbon fixation by Rubisco

C1.3.16 (HL)—Triose phosphate synthesis

C1.3.17 (HL)—RuBP regeneration

C1.3.18 (HL)—Synthesis of other compounds

C1.3.19 (HL)—Interdependence of light and light-independent reactions

C2.1 Chemical signalling [HL only]

C2.2 Neural signalling

C3.1 Integration of body systems

C3.2 Defence against disease

C4.1 Populations and communities

C4.2 Transfers of energy and matter

D Continuity and Change

D1.1 DNA replication

D1.2 Protein synthesis

D1.3 Mutation and gene editing

D2.1 Cell and nuclear division

D2.2 Gene expression [HL only]

D2.3 Water potential

D3.1 Reproduction

D3.2 Inheritance

D3.3 Homeostasis

D4.1 Natural selection

D4.2 Stability and change

D4.3 Climate change

IB Biology HL C1.3.15 (HL)—Carbon fixation by Rubisco Question Bank

• Rubisco fixes CO₂ to RuBP, forming glycerate 3-phosphate

• Rubisco is abundant but slow and limited by low CO₂

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