IB Biology Topic 1 Notes
This page contains our IB Biology notes for topic 1. By reading each one of these notes, you will fully cover the content for IB Biology 'Molecules & Metabolism'.
Chapters
A1.1: Water
A1.1: Origin of water (HL)
A1.2: Nucleic acids
A1.2: Further nucleic acids (HL)
B1.1: Carbohydrates and lipids
B1.2: Proteins
B1.2: Further proteins (HL)
C1.1: Enzymes & metabolism
C1.1: Further metabolism (HL)
C1.2: Respiration
C1.2: Further respiration (HL)
C1.3: Photosynthesis
C1.3: Further photosynthesis (HL)
D1.1: DNA replication
D1.1: Further DNA replication (HL)
D1.2: Protein synthesis
D1.2: Further protein synthesis (HL)
D1.3: Mutations
D1.3: Gene editing (HL)
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Structure of water
Water is the most essential molecule needed to sustain life on Earth. Also known as dihydrogen monoxide, it is composed of two hydrogen atoms covalently bonded to an oxygen atom. The sharing of electrons in these bonds is unequal, which means that water is a polar molecule!

Polar molecules with hydrogen and one of nitrogen, oxygen, or fluorine exhibit hydrogen bonding. Water fits this description, and thus exhibits hydrogen bonding between its molecules. Water’s polarity and its hydrogen bonding are the reason it is so versatile and the primary molecule we search for when attempting to detect alien life.
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