1. Molecules

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Understanding Points

Structure of water

Polar covalent bonds: unequal sharing of e⁻ → partially negative O atom, partially positive H atoms

Hydrogen bonding: intermolecular force between the O and H of different H₂O molecules

Understanding points

Structure of DNA

DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are the genetic material of all species

Nucleotide = phosphate group + pentose + nitrogenous base

A1.2 Nucleic acids

Understanding points

Carbon as the basis of life

Forms strong covalent bonds with other atoms to form stable molecules

Can form up to 4 covalent bonds and give rise to molecules with complex structures

B1.1 Carbohydrates and lipids

Understanding points

Amino acids

20 different types of naturally occurring 𝛼𝛼

*(AHL) R groups can be hydrophobic, hydrophilic, or charged

Understanding points

Enzymes

Biological catalysts that speed up the rate of reaction

Lower the activation energy (Eₐ) by providing alternative mechanism for the reaction

Active site: the specific binding site of a substrate

C1.1 Enzymes and metabolism

Understanding points

ATP

Adenosine triphosphate

Energy currency of the cell

C1.2 Cell respiration

Understanding points

Photosynthesis

Conversion of light energy to chemical energy by algae, plants, cyanobacteria

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Limiting factors: temperature, light intensity, CO₂ conc

C1.3 Photosynthesis

Understanding points

DNA replication

Occurs during S phase in interphase

Produces identical diploid daughter cells in mitosis

Semiconservative: each DNA molecule produced has one new strand and one parental strand

D1.1 DNA replication

Understanding points

Transcription

Production of mRNA from DNA by RNA polymerase 

D1.2 Protein synthesis

Understanding points

Mutation

A random, permanent change in the base sequence of DNA

Generates genetic variation upon which natural selection can act 

Mutagens: agents that increase the frequency of mutations above the natural background level

D1.3 Mutations and gene editing