JC1 H2 Biology vocabulary starts with understanding cells, proteins, membranes, DNA and inheritance. This guide gives 200 useful Biology terms with clear meanings and explains how to turn them into better diagrams, answers and scientific reasoning. It is aligned to the main ideas in the revised 2027 H2 Biology syllabus 9477 for Singapore-Cambridge A-Levels.
The list covers the full H2 course, so some terms belong to later JC work. Use the section connected to your current lecture first. A word becomes meaningful when you can draw it, describe its mechanism and apply it to a new question, not when you simply copy it into a notebook.
- Most useful early topics: cell organelles, biological molecules, enzymes, transport, DNA and genes.
- Later connections: cell cycle, metabolism, biological equilibrium, evolution, infectious disease and climate change.
- Scope note: these are 200 independently curated useful terms, not an official SEAB frequency ranking or a fixed JC1 teaching order.
How the 2027 H2 Biology syllabus is organised
SEAB lists four central ideas: the cell and biomolecules of life; genetics and inheritance; energy and equilibrium; and biological evolution. H2 also develops extension topics on infectious diseases and the impact of climate change on animals and plants. The subject asks students to connect evidence, mechanisms, ethics and real-world consequences rather than simply memorise biological labels.
Find your topic: 200 Biology vocabulary words
- Cell structure and microscopy (1–20)
- Biomolecules and protein structure (21–40)
- Enzymes, membranes and transport (41–60)
- DNA and nucleic acids (61–80)
- Gene expression and gene regulation (81–100)
- Cell division, inheritance and variation (101–120)
- Cellular energy and metabolism (121–140)
- Signalling and biological equilibrium (141–160)
- Evolution, biodiversity and adaptation (161–180)
- Infectious diseases, climate and scientific inquiry (181–200)
1. Cell structure and microscopy: terms 1–20
Look at a labelled cell diagram and ask what each structure actually does. A structure name without function is an incomplete explanation.
- Cell. The smallest structural and functional unit of living organisms.
- Prokaryote. An organism whose cells lack a membrane-bound nucleus.
- Eukaryote. An organism whose cells contain a nucleus and membrane-bound organelles.
- Organelle. A specialised subcellular structure carrying out a particular function.
- Nucleus. The compartment containing most genetic material in a eukaryotic cell.
- Nucleolus. A nuclear region involved in ribosomal RNA production and ribosome assembly.
- Cytoplasm. The material inside the cell membrane, excluding the nucleus.
- Cytosol. The liquid portion of cytoplasm in which many reactions occur.
- Plasma membrane. A selectively permeable boundary separating a cell from its surroundings.
- Ribosome. The molecular machine that translates messenger RNA into proteins.
- Endoplasmic reticulum. A membrane network involved in protein or lipid processing.
- Rough endoplasmic reticulum. An endoplasmic reticulum region bearing ribosomes for protein production.
- Smooth endoplasmic reticulum. A membrane network involved in lipid synthesis and other cell functions.
- Golgi apparatus. Membrane stacks that modify, sort and package cell products.
- Lysosome. A compartment containing enzymes used to digest cellular material.
- Mitochondrion. An organelle associated with aerobic respiration and ATP production.
- Chloroplast. A plant and algal organelle in which photosynthesis occurs.
- Cell wall. A supporting layer outside the plasma membrane in certain organisms.
- Magnification. The ratio of image size to actual specimen size.
- Resolution. The ability to distinguish two close objects as separate.
2. Biomolecules and protein structure: terms 21–40
Biomolecules are not just long names. The sequence, chemical bonds and arrangement of their units explain their useful properties.
- Monomer. A small building block from which larger molecules can be formed.
- Polymer. A large molecule made from repeating structural units.
- Carbohydrate. An organic biomolecule class including sugars, starch and cellulose.
- Monosaccharide. A simple sugar that cannot be hydrolysed into smaller sugars.
- Disaccharide. A carbohydrate made of two monosaccharides joined by a glycosidic bond.
- Polysaccharide. A carbohydrate made from many monosaccharide residues.
- Glycosidic bond. A covalent linkage joining sugar units.
- Lipid. A diverse class of molecules with low solubility in water.
- Triglyceride. A lipid formed from glycerol and three fatty acids.
- Phospholipid. A molecule with a hydrophilic head and hydrophobic tails, important in membranes.
- Amino acid. A small molecule containing amino and carboxyl functional groups.
- Peptide bond. A covalent bond linking amino-acid residues in proteins.
- Polypeptide. A chain of amino-acid residues joined by peptide bonds.
- Primary structure. The linear sequence of amino acids in a polypeptide.
- Secondary structure. Local protein folding patterns such as alpha helices and beta sheets.
- Tertiary structure. The overall three-dimensional folding of one polypeptide chain.
- Quaternary structure. The organisation of multiple polypeptide subunits in a protein.
- Hydrogen bond. An attraction involving a hydrogen bonded to an electronegative atom and an electron-rich partner.
- Disulfide bridge. A covalent bond joining cysteine side chains and stabilising some proteins.
- Denaturation. Loss of native molecular structure, often reducing biological function.
3. Enzymes, membranes and transport: terms 41–60
Distinguish passive transport from energy-dependent transport. Always state what moves, which direction it moves and why.
- Enzyme. A biological catalyst increasing reaction rate without being used up overall.
- Active site. An enzyme region where substrate binding and catalysis occur.
- Substrate. A molecule acted upon by an enzyme.
- Enzyme–substrate complex. A temporary association between enzyme and bound substrate.
- Activation energy. The energy barrier that must be overcome for a reaction.
- Specificity. The tendency of an enzyme or receptor to interact with particular molecules.
- Competitive inhibition. Reduced enzyme activity when an inhibitor competes for the active site.
- Non-competitive inhibition. Reduced enzyme activity through inhibitor binding outside the active site.
- Allosteric regulation. A change in protein activity caused by binding at a regulatory site.
- Diffusion. Net movement of particles down their concentration gradient.
- Osmosis. Net movement of water across a selectively permeable barrier due to water potential differences.
- Facilitated diffusion. Passive movement through membrane transport proteins down an electrochemical gradient.
- Active transport. Transport against a gradient using an energy source.
- Channel protein. A membrane protein forming a passage for selected ions or molecules.
- Carrier protein. A membrane protein changing shape to move a specific substance.
- Endocytosis. Uptake of material through inward membrane budding.
- Exocytosis. Release of material through fusion of vesicles with the plasma membrane.
- Water potential. A measure of water’s chemical potential relative to reference conditions.
- Hypertonic solution. A solution with greater effective solute concentration than the reference cell.
- Hypotonic solution. A solution with lower effective solute concentration than the reference cell.
4. DNA and nucleic acids: terms 61–80
DNA structure supports copying and information storage. Sequence matters, but the mechanism of replication explains inheritance.
- Nucleotide. The basic unit of nucleic acids, consisting of base, sugar and phosphate.
- DNA. Deoxyribonucleic acid, the usual hereditary information store in cellular life.
- RNA. Ribonucleic acid, involved in gene expression and several cellular processes.
- Deoxyribose. The five-carbon sugar found in DNA nucleotides.
- Ribose. The five-carbon sugar present in RNA nucleotides.
- Nitrogenous base. A nitrogen-containing component of a nucleotide involved in base pairing.
- Complementary base pairing. Specific pairing such as A–T and G–C in DNA.
- Antiparallel strands. Two nucleic-acid strands oriented in opposite 5′ to 3′ directions.
- Double helix. The twisted two-stranded architecture of DNA.
- Hydrogen bonding in DNA. Attractions linking complementary bases across DNA strands.
- Phosphodiester bond. A covalent linkage joining nucleotides along a nucleic-acid backbone.
- Chromosome. A packaged DNA molecule associated with proteins.
- Chromatin. DNA and its associated proteins within a eukaryotic nucleus.
- Gene. A DNA sequence that contributes to a functional RNA or protein product.
- Genome. The complete hereditary DNA information of an organism or entity.
- DNA replication. The process of copying DNA before cell division.
- Semi-conservative replication. DNA copying in which each daughter molecule retains one parental strand.
- DNA polymerase. An enzyme adding nucleotides to a growing DNA strand.
- Helicase. An enzyme that separates paired DNA strands during replication.
- Replication fork. A Y-shaped region where DNA is opened for copying.
5. Gene expression and gene regulation: terms 81–100
DNA does not directly become a protein. Cells transcribe DNA information into RNA and translate a coding message into a polypeptide.
- Transcription. Synthesis of an RNA molecule from a DNA template.
- Translation. Synthesis of a polypeptide using information carried by messenger RNA.
- Messenger RNA. RNA carrying a coding sequence to the translation machinery.
- Transfer RNA. RNA carrying amino acids and recognising codons during translation.
- Ribosomal RNA. RNA forming essential structural and catalytic parts of ribosomes.
- Codon. A three-nucleotide sequence in coding RNA specifying an amino acid or stop signal.
- Anticodon. A three-nucleotide region of tRNA pairing with an mRNA codon.
- Promoter. A DNA region involved in starting transcription.
- Terminator. A sequence or signal leading to termination of transcription.
- RNA polymerase. An enzyme that synthesises RNA using a nucleic-acid template.
- Splicing. Removal of introns and joining of exons in RNA processing.
- Intron. A transcribed sequence removed during RNA splicing.
- Exon. A sequence retained in mature processed RNA.
- Gene regulation. Control over when and how much a gene is expressed.
- Transcription factor. A protein influencing transcription by interacting with regulatory regions or machinery.
- Enhancer. A regulatory DNA sequence that can increase transcription.
- Repressor. A molecule that decreases gene expression under specified conditions.
- Epigenetic modification. A chemical change affecting chromatin or gene activity without changing DNA sequence.
- DNA methylation. Addition of methyl groups to DNA, often influencing gene regulation.
- Operon. A prokaryotic gene-regulatory unit with linked control of multiple genes.
6. Cell division, inheritance and variation: terms 101–120
Mitosis, meiosis and fertilisation answer different biological questions. Use chromosome diagrams rather than relying only on their names.
- Cell cycle. The ordered events of growth, DNA replication and cell division.
- Interphase. The period during which cells grow and usually duplicate DNA.
- Mitosis. Nuclear division producing genetically similar daughter nuclei under normal circumstances.
- Meiosis. Cell division producing haploid cells after one DNA replication and two divisions.
- Cytokinesis. Division of the cytoplasm to form separate daughter cells.
- Diploid. Having two chromosome sets, conventionally written 2n.
- Haploid. Having one chromosome set, conventionally written n.
- Homologous chromosomes. Chromosomes carrying corresponding gene loci, one from each parent in diploid organisms.
- Sister chromatids. Duplicated chromosome copies joined before separation.
- Crossing over. Exchange of corresponding DNA segments between non-sister chromatids in meiosis.
- Independent assortment. Random orientation of homologous chromosome pairs in meiosis.
- Allele. An alternative version of a gene at a particular locus.
- Genotype. The genetic constitution of an organism at specified loci.
- Phenotype. The observable traits arising from genotype and environment.
- Dominant allele. An allele expressed in the heterozygous condition for the trait considered.
- Recessive allele. An allele whose effect is masked by a dominant allele in a heterozygote.
- Homozygous. Having two identical alleles at a specified locus.
- Heterozygous. Having two different alleles at a specified locus.
- Mutation. A heritable change in nucleotide sequence.
- Pedigree. A diagram tracing inheritance of a trait through a family.
7. Cellular energy and metabolism: terms 121–140
Trace matter and energy separately. Cells transfer energy through chemical reactions while atoms are rearranged rather than disappearing.
- Metabolism. The total set of chemical reactions occurring in a cell or organism.
- Anabolism. Energy-requiring pathways building larger molecules from smaller ones.
- Catabolism. Pathways breaking down molecules and often releasing usable energy.
- ATP. Adenosine triphosphate, a principal immediate energy-transfer molecule.
- ADP. Adenosine diphosphate, formed when ATP loses a phosphate group.
- Respiration. A set of reactions transferring energy from organic molecules into usable forms.
- Aerobic respiration. Respiration in which oxygen acts as the terminal electron acceptor.
- Anaerobic respiration. Respiratory energy production using a terminal electron acceptor other than oxygen.
- Glycolysis. A cytosolic pathway converting glucose to pyruvate while generating ATP and reduced carriers.
- Pyruvate. A three-carbon molecule produced by glycolysis.
- Krebs cycle. A cyclic pathway oxidising acetyl groups and producing reduced electron carriers.
- Electron transport chain. Membrane-associated carriers transferring electrons through redox reactions.
- Chemiosmosis. ATP synthesis coupled to proton movement down an electrochemical gradient.
- Oxidative phosphorylation. ATP synthesis driven by an electron-transport-generated proton gradient.
- Fermentation. A pathway regenerating electron acceptors during ATP production without an electron transport chain.
- Photosynthesis. Conversion of light energy into chemical energy in organic molecules.
- Chlorophyll. A light-absorbing pigment central to photosynthetic energy capture.
- Light-dependent reactions. Photosynthetic reactions generating ATP and reduced electron carriers using light.
- Calvin cycle. The carbon-fixation reactions of photosynthesis.
- Carbon fixation. The incorporation of inorganic carbon into organic molecules.
8. Signalling and biological equilibrium: terms 141–160
Feedback systems must be described as loops: stimulus, receptor, response and how the response affects the original deviation.
- Homeostasis. Regulation of internal conditions within ranges compatible with functioning.
- Negative feedback. A control response opposing the original deviation.
- Positive feedback. A response amplifying the original change until a limiting event occurs.
- Receptor. A structure or protein detecting a signal.
- Ligand. A molecule that binds specifically to another molecule, such as a receptor.
- Signal transduction. Conversion of an external or internal signal into cellular responses.
- Second messenger. An intracellular molecule relaying a signal from a receptor.
- Hormone. A signalling substance affecting target cells through specific interactions.
- Target cell. A cell possessing the machinery to respond to a particular signal.
- Cell communication. Transfer and interpretation of information between or within cells.
- Signal amplification. An increase in downstream response from a small initiating signal.
- Phosphorylation. Addition of a phosphate group, often changing a protein’s activity.
- Dephosphorylation. Removal of a phosphate group by a phosphatase.
- Kinase. An enzyme transferring phosphate groups to target molecules.
- Phosphatase. An enzyme removing phosphate groups from molecules.
- Ion channel. A protein passage enabling selected ions to cross a membrane.
- Membrane potential. The electrical potential difference across a biological membrane.
- Concentration gradient. A difference in solute concentration between two locations.
- Steady state. A condition with relatively stable measurements despite continuing processes.
- Biological equilibrium. A balanced condition in a system; distinct from a completely inactive state.
9. Evolution, biodiversity and adaptation: terms 161–180
Evolution concerns changing populations, not purposeful change by individual organisms. Explain heritable variation and differential reproduction.
- Evolution. Change in inherited characteristics of populations across generations.
- Natural selection. Differential survival and reproduction associated with heritable variation.
- Adaptation. A heritable feature increasing fitness under specified environmental conditions.
- Fitness. An organism’s relative reproductive success in a given environment.
- Selection pressure. An environmental factor changing relative survival or reproductive success.
- Variation. Differences among individuals in a population.
- Genetic drift. Random changes in allele frequencies, especially influential in small populations.
- Gene flow. Transfer of alleles between populations through migration and reproduction.
- Allele frequency. The proportion of a specified allele among the corresponding alleles in a population.
- Population. Organisms of the same species occupying a defined place at a given time.
- Species. A classification unit, often described by reproductive compatibility for sexual organisms.
- Speciation. The evolutionary formation of distinct species.
- Reproductive isolation. Barriers preventing gene exchange between populations.
- Allopatric speciation. Speciation following geographic separation of populations.
- Sympatric speciation. Speciation without geographic separation of populations.
- Biodiversity. The variety of life at genetic, species and ecosystem levels.
- Phylogeny. The evolutionary history and relationships of organisms.
- Clade. An ancestor and all of its descendants.
- Common ancestor. An ancestral lineage shared by two or more descendants.
- Antibiotic resistance. The ability of microbes to survive antimicrobial treatment, often selected by exposure.
10. Infectious diseases, climate and scientific inquiry: terms 181–200
Biology is part of public life. Pathogens, immunity, climate and sampling methods require careful interpretation of evidence.
- Pathogen. A biological agent capable of causing disease.
- Infection. The entry and multiplication of a pathogen within a host.
- Transmission. The movement of a pathogen from one host or reservoir to another.
- Virulence. The degree of harm a pathogen can cause.
- Reservoir. A host or environment where an infectious agent persists.
- Vector. An organism transferring a pathogen between hosts.
- Epidemic. A disease occurrence exceeding the expected level in a defined population.
- Pandemic. An epidemic spreading across several countries or continents.
- Immunity. Protection against infection or disease through host defence mechanisms.
- Antigen. A molecular feature recognised by the immune system.
- Antibody. An immunoglobulin binding a specific antigenic structure.
- Vaccination. Administration of a preparation intended to induce protective immune responses.
- Herd immunity. Indirect population protection when sufficient members are immune.
- Climate change. A long-term shift in climate patterns, including temperature and rainfall.
- Greenhouse gas. An atmospheric gas absorbing and emitting thermal infrared radiation.
- Carbon cycle. The movement of carbon through the atmosphere, biosphere, oceans and Earth systems.
- Ecological niche. The functional role and resource relationships of a species within an ecosystem.
- Sampling bias. A systematic distortion introduced by how observations or specimens are selected.
- Control variable. A factor held constant to isolate the relationship being investigated.
- Scientific hypothesis. A testable explanation or prediction evaluated through evidence.
Worked example 1: diffusion, osmosis and active transport
A red blood cell placed in a sufficiently hypotonic solution may gain water by osmosis and swell. This is not simply ‘water diffusing because there is more water outside’. Osmosis concerns the net movement of water across a selectively permeable membrane in response to water-potential differences. By contrast, an ion transported against its electrochemical gradient may require energy-dependent active transport. Defining what moves and what supplies the driving force prevents vague explanations.
Worked example 2: from a gene to a protein
Begin with a gene’s DNA sequence. During transcription, an RNA molecule is synthesised using the DNA template. In eukaryotic cells, processing can remove introns and join exons to produce mature RNA. During translation, ribosomes read mRNA codons and link amino acids into a polypeptide. A mutation may affect the sequence or expression of the product, but not every mutation changes the resulting amino-acid sequence or phenotype. That last qualification matters in examination explanations.
Worked example 3: evolution and antibiotic resistance
Suppose some bacteria already possess heritable variants that survive an antibiotic. Exposure can favour these variants, allowing them to reproduce and become more common. The antibiotic does not deliberately teach each bacterium how to resist treatment. The correct vocabulary is heritable variation, selection pressure, differential survival and allele frequency. This framework is also useful when reading medical and public-health reporting.
Worked example 4: biological evidence and climate change
A warming environment may affect the distribution, life cycles and interactions of species. To evaluate a claim, separate the observation from the proposed mechanism, look for comparison groups and consider sampling bias and alternative explanations. Biology connects microscopic processes with ecosystems, but scientific conclusions must remain proportional to the evidence.
A calm four-week study plan
- Week 1: Learn 40 current-topic words using a diagram, definition and function beside each.
- Week 2: Add another 40, especially mechanism words such as transcription, diffusion, inhibition and regulation. Explain the process in the correct order.
- Week 3: Distinguish confusing pairs, including genotype and phenotype; mitosis and meiosis; active transport and facilitated diffusion; gene and allele.
- Week 4: Attempt unfamiliar application questions. For each mistake, identify the exact biological term you misunderstood and rewrite the answer with one explicit cause-and-effect link.
Frequently asked questions
Are all 200 words taught in JC1?
No. This resource spans the full H2 syllabus and may introduce vocabulary that your school teaches in JC2. Follow the order of your college lessons while using later terms as a reference.
What is the 2027 H2 Biology syllabus code?
9477. The revised 2027 H2 Biology document should be used when checking what is examinable, rather than treating older 9744 guidance as necessarily current.
Do I need to memorise definitions word for word?
Know exact scientific distinctions, but practise explaining mechanisms in your own clear language. For some assessment questions precise terminology is essential; for others application and reasoning determine whether the answer is complete.
How should I revise long biological processes?
Draw a sequence of steps, label the participants and indicate cause-and-effect arrows. Explain what would happen if a component were removed or changed.
Can a student enter JC H2 Biology from combined Science?
Admission into a particular H2 subject depends on the junior college’s requirements and available combinations. Consult the college directly; the syllabus glossary itself does not determine eligibility.
Official syllabus and connected reading
Check the official SEAB H2 Biology syllabus 9477 for 2027 and the A-Level 2027 syllabus index. For subject decisions, read Why study JC H2 Biology? and Can a student take H2 Biology with combined Science?. Explore eduKate Singapore for further learning routes.
Teaching guide
Assess each term through three linked questions: what is it, how does it work, and what changes when one condition changes? Biological vocabulary is a set of explanations, not a list of spelling words. Encourage diagrams, evidence and precise cause-and-effect language.