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

B2.1.1—Lipid bilayers as basis

B2.1.2—Bilayers as barriers

B2.1.3—Simple diffusion

B2.1.4—Integral and peripheral proteins

B2.1.5—Osmosis and aquaporins

B2.1.6—Channel proteins

B2.1.7—Pump proteins

B2.1.8—Selectivity in permeability

B2.1.9—Glycoproteins and glycolipids

B2.1.10—Fluid mosaic model

B2.1.11 (HL)—Fatty acid composition and fluidity

B2.1.12 (HL)—Cholesterol and fluidity

B2.1.13 (HL)—Membrane fluidity and vesicles

B2.1.14 (HL)—Gated ion channels in neurons

B2.1.15 (HL)—Sodium-potassium pumps

B2.1.16 (HL)—Sodium-glucose cotransporters

B2.1.17 (HL)—Cell adhesion molecules (CAMs)

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

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 B2.1.11 (HL)—Fatty acid composition and fluidity Question Bank

• Unsaturated fatty acid tails have kinks and increase membrane fluidity

• Saturated fatty acid tails pack closely and strengthen membranes at higher temperatures

• Homeoviscous adaptation changes lipid composition with temperature, as in lake sturgeon

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