A full study booklet covering Biology and Chemistry for Grade 9 and 10. Built bite-size for 1-hour daily sessions. You've got this.
One hour a day. Alternating between Bio and Chem. Each session has a clear focus — start, do, done. No overwhelm.
Every living thing is made of cells — the smallest unit of life. In IB biology, your first big job is understanding the difference between the two fundamental cell types.
Prokaryotic cells (like bacteria) have no membrane-bound nucleus. Their DNA floats freely in the cytoplasm. They are small (1–10 µm) and were the first life on Earth.
Eukaryotic cells (like yours) have a nucleus surrounded by a membrane. They contain organelles — specialised compartments each with a job. Animal, plant, and fungal cells are all eukaryotic.
The fluid mosaic model describes the cell membrane: a phospholipid bilayer with proteins embedded throughout. It controls what enters and leaves the cell.
Movement across membranes happens three ways: diffusion (passive, high to low), osmosis (water across a semi-permeable membrane), and active transport (against the gradient, uses ATP).
The cell cycle has three phases: Interphase (G1, S, G2), Mitosis, and Cytokinesis. Mitosis produces two identical daughter cells. When this process goes wrong — cancer can form.
DNA (deoxyribonucleic acid) is the molecule of inheritance. It forms a double helix — two strands wound around each other, held together by base pairs. The bases are: Adenine–Thymine (A-T) and Cytosine–Guanine (C-G). Remember: A pairs with T, C pairs with G.
A gene is a section of DNA that codes for a protein. The different versions of a gene are called alleles. Alleles can be dominant (expressed even with one copy, written as capital) or recessive (only expressed with two copies, written as lowercase).
Your genotype is the alleles you carry (e.g. Bb). Your phenotype is the physical trait expressed (e.g. brown eyes). If both alleles are the same = homozygous. If different = heterozygous.
Punnett squares predict the probability of offspring genotypes and phenotypes. In codominance, both alleles are expressed equally (e.g. blood type AB). Sex-linked traits are carried on the X chromosome — more common in males (XY) than females (XX).
Mutations are changes in the DNA sequence. They can be spontaneous or caused by mutagens (UV radiation, certain chemicals). Not all mutations are harmful — some are neutral, and occasionally beneficial.
At G10 level, you go deeper into how DNA actually works. Transcription converts DNA into mRNA in the nucleus. Translation reads the mRNA at ribosomes to build proteins from amino acids.
The genetic code is a triplet code — every three bases (a codon) codes for one amino acid. There are 20 amino acids and 64 possible codons, so the code is degenerate (multiple codons for the same amino acid).
DNA replication is semi-conservative: each new DNA molecule contains one old strand and one new strand. The enzyme helicase unwinds the double helix; DNA polymerase adds new complementary bases.
Proteins are central to biology — enzymes, hormones, antibodies, and structural proteins. The shape of a protein determines its function. Enzymes are biological catalysts: they lower activation energy, have an active site complementary to their substrate, and are affected by temperature and pH.
Everything is made of atoms. An atom has a nucleus (protons + neutrons) surrounded by electrons in shells. The number of protons = atomic number (Z). The total of protons + neutrons = mass number (A).
Isotopes are atoms of the same element with different numbers of neutrons (different mass number, same atomic number). For example, Carbon-12 and Carbon-14 are both carbon, but C-14 has 2 extra neutrons.
Electrons fill shells in order: shell 1 holds max 2, shell 2 holds max 8, shell 3 holds max 8 (at this level). The number of electrons in the outermost shell (valence electrons) determines reactivity and chemical behaviour.
The periodic table is arranged by increasing atomic number. Elements in the same group have the same number of valence electrons and similar properties. Periods (rows) correspond to number of electron shells.
Periodic trends: atomic radius decreases across a period (more protons pull electrons closer); ionisation energy increases across a period. Both reverse down a group.
Atoms bond to achieve a full outer electron shell (usually 8 — the octet rule). There are three main types of bonding in IB Chemistry.
Ionic bonding: a metal gives electrons to a non-metal. The metal becomes a positive ion (cation); the non-metal becomes a negative ion (anion). Electrostatic attraction holds the lattice together. Ionic compounds have high melting points, conduct electricity when dissolved or melted, and are usually solid at room temperature.
Covalent bonding: two non-metals share electron pairs. Can be single (sharing 1 pair), double (2 pairs), or triple (3 pairs) bonds. Covalent molecules generally have lower melting points and don't conduct electricity.
Metallic bonding: metal cations sit in a sea of delocalised electrons. This explains why metals conduct electricity and heat, are malleable, and have high melting points.
VSEPR theory predicts molecular shape based on the number of electron pairs around the central atom. Linear (CO₂), trigonal planar (BF₃), tetrahedral (CH₄), bent (H₂O).
The mole is the chemist's counting unit. 1 mole = 6.022 × 10²³ particles (Avogadro's number). This connects the microscopic world of atoms to measurable masses in the lab.
Molar mass (M) is the mass of one mole of a substance in g/mol. It equals the relative atomic/molecular mass from the periodic table. For example, 1 mol of H₂O = 18 g/mol.
The core formula: n = m / M (moles = mass ÷ molar mass). Master this — it comes up in every stoichiometry problem.
Stoichiometry uses balanced equations to calculate how much reactant you need or how much product you'll make. The coefficients in a balanced equation give mole ratios. The limiting reagent is the one that runs out first and determines how much product forms.
Percentage yield = (actual yield / theoretical yield) × 100%. Real reactions are rarely 100% efficient.
Acids donate protons (H⁺ ions) to solution. Bases accept protons. This is the Brønsted-Lowry definition. The pH scale runs 0–14: acidic (pH <7), neutral (pH 7), basic/alkaline (pH >7). Each unit is 10× difference in concentration.
Strong acids (HCl, H₂SO₄, HNO₃) fully dissociate in water. Weak acids (ethanoic acid, carbonic acid) partially dissociate. The same applies for bases.
Acid + Base → Salt + Water (neutralisation). Acid + Metal → Salt + Hydrogen. Acid + Carbonate → Salt + Water + CO₂.
Redox reactions: Oxidation = loss of electrons; Reduction = gain of electrons. Remember: OIL RIG (Oxidation Is Loss, Reduction Is Gain). In every redox reaction, one species is oxidised while another is reduced simultaneously.
Oxidation state (or oxidation number) tracks electron changes. It helps identify what's oxidised and what's reduced in complex reactions.
For IB DP → Medicine, you'll almost certainly need both HL Biology AND HL Chemistry. Here's exactly what that means and how to prepare from where you are now.
Nearly every medical school worldwide requires HL Biology for IB students. It covers biochemistry, genetics, physiology, and ecology at a level that directly feeds into medical school curricula.
Topics you're building now (cell biology, DNA, genetics) are the exact foundations of HL Bio Units 1–4. Starting to love this content in Grade 9 is a real advantage.
→ Your G9 and G10 Biology directly prepares you for this.
HL Chemistry is required or strongly recommended for medicine. Pharmacology, biochemistry, and physiology are deeply chemical. Understanding how drugs work, how the body metabolises compounds, and how lab tests function all require strong chemistry.
Organic chemistry (which you'll start in G10) is especially important — the structure of drugs, amino acids, and metabolic molecules are all organic chemistry.
→ Your G9 and G10 Chem gives you the language you need.
Most pre-med IB students take: HL Bio + HL Chem + HL Maths AA (Analysis & Approaches). Maths is required by many universities for science degrees.
If Maths is very difficult, HL Psychology is a strong alternative — it links well to medicine and is very manageable alongside HL Bio + Chem.
Grade 9 is the ideal time to build the foundations. You don't need to be perfect now — you need to understand the core ideas, build study habits, and develop genuine interest.
Your 1-hour daily sessions, your curiosity, and your ambition toward medicine are all exactly what's needed. The students who succeed in HL Bio and Chem are the ones who started caring early. That's you.