IGCSE Biology – Units 1-5 Core Vocabulary

A comprehensive set of vocabulary flashcards covering key terms and definitions from Units 1-5 of IGCSE Biology: characteristics of life, classification, cell structure, transport processes, biological molecules and enzyme activity.

Movement

An action by an organism or part of an organism causing a change of position or place.

Respiration

Chemical reactions in cells that break down nutrient molecules and release energy for metabolism.

Sensitivity

Ability of an organism to detect and respond to changes in its internal or external environment.

Growth

A permanent increase in size and dry mass of an organism.

Reproduction

Biological process that produces new individuals of the same kind.

Excretion

Removal of waste products of metabolism and substances in excess of requirements.

Nutrition

Intake of materials for energy, growth and development.

Species

Group of organisms capable of interbreeding to produce fertile offspring.

Classification hierarchy

Ordered groups: Kingdom > Phylum > Class > Order > Family > Genus > Species.

Binomial naming system

International system giving every species a two-part scientific name: Genus species (italicised).

Dichotomous key

Tool using pairs of contrasting statements to identify organisms by visible features.

Animal kingdom

Multicellular ingestive heterotrophs with nuclei but no cell walls or chloroplasts.

Plant kingdom

Multicellular photosynthetic autotrophs with cellulose cell walls and often chloroplasts.

Fungus kingdom

Organisms with chitin cell walls that feed saprophytically or parasitically; often form hyphae and mycelium.

Protoctist kingdom

Diverse unicellular or multicellular eukaryotes that may have cell walls or chloroplasts; some photosynthesise, others ingest.

Prokaryote kingdom

Unicellular organisms lacking a true nucleus; have peptidoglycan cell walls and circular DNA.

Vertebrate

Animal possessing a backbone.

Mammal

Warm-blooded vertebrate with hair, mammary glands, placenta and a four-chambered heart.

Bird

Warm-blooded vertebrate with feathers, beak, wings and hard-shelled eggs.

Reptile

Cold-blooded vertebrate with dry scaly skin; lays soft waterproof eggs on land.

Amphibian

Cold-blooded vertebrate with moist skin; undergoes aquatic larval stage and metamorphosis.

Fish

Cold-blooded aquatic vertebrate with gills, fins and scaly skin.

Arthropod

Invertebrate with jointed limbs, segmented body and waterproof exoskeleton.

Crustacean

Arthropod with more than four pairs of legs and two pairs of antennae; no wings.

Arachnid

Arthropod with four pairs of legs, two body parts, no antennae or wings.

Insect

Arthropod with three pairs of legs, two pairs of wings, one pair of antennae and three body segments.

Myriapod

Arthropod with many body segments, each bearing jointed legs; one pair of antennae.

Flowering plant

Plant that reproduces by flowers and seeds formed inside an ovary.

Dicotyledon

Flowering plant whose seed has two cotyledons, net-veined broad leaves and floral parts in 4s or 5s.

Monocotyledon

Flowering plant whose seed has one cotyledon, parallel-veined narrow leaves and floral parts in 3s.

Fern

Non-flowering plant with roots, stems and leaves that reproduces by spores on fronds.

Virus

Non-living particle of nucleic acid in a protein coat that reproduces only inside host cells.

Cell membrane

Partially permeable boundary controlling movement of substances into and out of the cell.

Cytoplasm

Jelly-like substance where metabolic reactions occur.

Nucleus

Organelle containing DNA; controls cell activities.

Mitochondrion

Organelle where aerobic respiration releases energy; inner membrane folded for large surface area.

Ribosome

Tiny organelle responsible for protein synthesis.

Rough endoplasmic reticulum

Membranous network studded with ribosomes; transports and folds proteins.

Vacuole

Fluid-filled sac in plant cells containing cell sap; keeps cell turgid.

Cell wall

Rigid, fully permeable layer outside plant, fungal or bacterial cells; provides support.

Chloroplast

Plant organelle containing chlorophyll for photosynthesis.

Prokaryote

Cell without membrane-bound nucleus; DNA is a circular loop in cytoplasm.

Plasmid

Small circular DNA molecule in bacteria used in genetic engineering.

Flagellum

Long whip-like projection enabling movement in some bacteria.

Light microscope

Instrument that uses light and glass lenses to magnify specimens.

Electron microscope

Instrument that uses electron beams for high-resolution imaging of cell ultrastructure.

Tissue

Group of similar cells working together to perform a function.

Organ

Structure made of different tissues performing a specific function.

Organ system

Group of organs working together to perform body functions.

Ciliated cell

Epithelial cell with cilia that move mucus in trachea and bronchi.

Root hair cell

Elongated root epidermal cell increasing surface area for water and mineral absorption.

Neuron

Nerve cell specialised for rapid conduction of electrical impulses.

Palisade mesophyll cell

Column-shaped leaf cell packed with chloroplasts for photosynthesis.

Red blood cell

Biconcave blood cell containing haemoglobin to transport oxygen.

Sperm cell

Male gamete with flagellum specialized for fertilising an egg.

Egg cell

Large female gamete containing nutrients for embryo development.

Diffusion

Passive net movement of particles from high to low concentration due to random motion.

Osmosis

Passive movement of water molecules from higher to lower water potential through a partially permeable membrane.

Active transport

Energy-dependent movement of particles against a concentration gradient via carrier proteins.

Turgid

State of a plant cell swollen with water; vacuole presses against cell wall.

Plasmolysis

Shrinkage of plant cell contents away from cell wall due to water loss.

Dialysis tubing

Artificial partially permeable membrane used to model diffusion and osmosis.

Endocytosis (phagocytosis)

Uptake of large particles by engulfing them with the cell membrane.

Carbohydrate

Organic molecule of C, H and O; includes sugars, starch, cellulose and glycogen.

Monosaccharide

Single-sugar unit such as glucose or fructose; soluble in water.

Disaccharide

Sugar formed from two monosaccharides, e.g., sucrose or maltose.

Polysaccharide

Long chain of monosaccharides; insoluble or less soluble, e.g., starch, glycogen, cellulose.

Cellulose

Straight-chain polysaccharide forming plant cell walls; indigestible to humans.

Starch

Spiral polysaccharide storing energy in plants.

Glycogen

Branched polysaccharide storing energy in animals.

Lipid

Fat or oil made from glycerol and fatty acids; long-term energy store and insulation.

Fatty acid

Long hydrocarbon acid component of lipids.

Glycerol

Three-carbon alcohol backbone of triglycerides and phospholipids.

Protein

Polymer of amino acids containing C, H, O, N (sometimes S); forms enzymes, antibodies etc.

Amino acid

Building block of proteins; 20 types combine in various sequences.

Nucleic acid

Polymer of nucleotides; includes DNA and RNA.

DNA

Double-helix nucleic acid storing genetic information with complementary base pairing.

Complementary base pairing

In DNA, adenine pairs with thymine and cytosine with guanine.

Benedict’s test

Chemical test for reducing sugars producing green, yellow or red precipitate on heating.

Iodine test

Starch test turning blue-black in presence of starch.

Biuret test

Protein test giving purple colour when peptide bonds present.

Emulsion (ethanol) test

Lipid test producing cloudy white suspension after ethanol and water are added.

DCPIP test

Vitamin C test where blue DCPIP becomes colourless when reduced.

Catalyst

Substance that increases reaction rate without being used up.

Enzyme

Biological protein catalyst that speeds up metabolic reactions.

Active site

Region on an enzyme where the substrate binds.

Substrate

Reactant molecule on which an enzyme acts.

Enzyme-substrate complex

Temporary association between enzyme and substrate during catalysis.

Lock and key model

Theory that enzyme active site fits only its specific substrate.

Enzyme specificity

Property whereby an enzyme catalyses only one particular reaction or type of reaction.

Optimum temperature

Temperature at which an enzyme’s activity is fastest.

Optimum pH

pH at which an enzyme shows maximum activity.

Denaturation

Irreversible change in protein shape causing loss of enzyme activity.

Carbohydrase

Enzyme class that digests carbohydrates into simple sugars.

Amylase

Carbohydrase that breaks starch into maltose.

Maltase

Enzyme that splits maltose into two glucose molecules.

Sucrase

Enzyme that hydrolyses sucrose into glucose and fructose.

Lactase

Enzyme that hydrolyses lactose into glucose and galactose.

Lipase

Enzyme that digests lipids into fatty acids and glycerol.

Protease

Enzyme that breaks proteins into amino acids.