Edexcel IGCSE Biology: Characteristics of Life, Cell Biology, and Core Physiology

Comprehensive vocabulary flashcards covering the key terms, biological molecules, cell structures, organism classifications, and ecological/genetic principles from the Pearson Edexcel IGCSE Biology specification.

Nutrition

The taking in of materials for energy, growth, and development.

Respiration

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

Excretion

The removal of waste products of metabolism and substances in excess of requirements (such as carbon dioxide, urea, and excess water).

Sensitivity

The ability to detect and respond to changes in the internal or external environment.

Movement

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

Homeostasis

The maintenance of a constant, stable internal environment (such as body temperature, blood glucose concentration, and water balance).

Reproduction

The processes that make more of the same kind of organism, either sexually or asexually.

Growth

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

Development

The changes that occur as an organism becomes mature.

Organelle

A specialized sub-cellular structure that performs a specific function inside a cell.

Cell

The basic structural and functional unit of all living organisms.

Tissue

A group of similar cells working together to perform a shared function.

Organ

A structure made of a group of different tissues working together to perform specific bodily functions.

Organ System

A group of organs working together to carry out a particular body process or function.

Organism

A complete living entity capable of carrying out all life processes.

Nucleus

An organelle that controls cell activity and contains genetic material (DNA).

Cytoplasm

The jelly-like fluid inside a cell where most metabolic chemical reactions take place.

Cell Membrane

A partially permeable membrane that regulates the movement of substances into and out of the cell.

Mitochondria

Organelles that serve as the site of aerobic respiration, releasing energy (ATP) for the cell.

Cell Wall

A rigid external layer that provides structural support; composed of cellulose in plants, chitin in fungi, and peptidoglycan in bacteria.

Chloroplast

An organelle containing chlorophyll that absorbs light energy to carry out photosynthesis.

Vacuole

A large central organelle in plant cells filled with cell sap that maintains turgor pressure and structural rigidity.

Eukaryote

An organism whose cells contain a distinct membrane-bound nucleus and membrane-bound organelles (includes plants, animals, fungi, and protoctists).

Prokaryote

A microscopic single-celled organism (such as bacteria) that lacks a nucleus and membrane-bound organelles, possessing circular naked DNA and plasmids.

Saprotrophic Nutrition

A mode of fungal feeding involving the extracellular secretion of digestive enzymes onto food and subsequent absorption of the digested organic products.

Hyphae

Thread-like branching fungal structures containing many nuclei, which weave together to form a mycelium.

Mycelium

The vegetative, thread-like network of hyphae that constitutes the body of a multicellular fungus.

Pathogen

Any microorganism or infectious agent capable of causing disease in another organism, including bacteria, fungi, protoctists, or viruses.

Virus

A non-living, parasitic, acellular particle smaller than bacteria composed of a protein coat (capsid) enclosing DNA or RNA, capable of reproducing only inside living host cells.

Lactobacillus bulgaricus

A rod-shaped bacterium used commercially in the fermentation of milk to produce yoghurt.

Pneumococcus

A spherical, pathogenic bacterium responsible for causing pneumonia.

Plasmodium

A microscopic, pathogenic protoctist that causes malaria in humans.

Benedict's Test

A biochemical test for reducing sugars; when heated in a water bath with Benedict's reagent, a positive solution changes from blue to green, yellow, orange, and finally brick-red / red-brown.

Iodine Test

A biochemical test for starch; the addition of yellow-brown iodine solution produces a blue-black colour if starch is present.

Emulsion Test

A biochemical test for lipids; dissolving the sample in ethanol and adding water produces a cloudy/milky emulsion if lipids are present.

Biuret Test

A biochemical test for proteins; the addition of Biuret reagent turns the solution from blue to purple/violet when protein is present.

Enzyme

A protein molecule that acts as a biological catalyst, speeding up metabolic reactions without being consumed.

Active Site

The specific region of an enzyme molecule where complementary substrate molecules bind to undergo a catalyzed reaction.

Diffusion

The net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient.

Osmosis

The net movement of water molecules from a solution of higher water potential to a solution of lower water potential across a partially permeable membrane.

Active Transport

The movement of substances across a cell membrane against a concentration gradient, requiring metabolic energy released by ATP.

ATP

A high-energy molecule produced during cellular respiration that provides energy directly for metabolic processes in cells.

Aerobic Respiration

The breakdown of glucose in cells in the presence of oxygen to release substantial energy (ATP), producing carbon dioxide and water.

Anaerobic Respiration

The breakdown of glucose in cells in the absence of oxygen, yielding lactate in animals and ethanol plus carbon dioxide in yeast and plants.

Alveoli

Microscopic air sacs in the lungs adapted for efficient gas exchange by having a large surface area, very thin walls, and an extensive capillary network.

Phagocytes

A type of white blood cell that defends against disease by engulfing, ingesting, and digesting pathogenic microorganisms.

Lymphocytes

A type of white blood cell that secretes specific antibodies targeted against antigens on invading pathogens.

Population

All the individuals of a single species living within a particular habitat at the same time.

Community

All the populations of different species living and interacting together in the same area.

Ecosystem

A distinct biological community of interacting organisms and their physical abiotic environment.

Trophic Level

The position that an organism occupies in a food chain, food web, or ecological pyramid.

10% Energy Transfer Rule

The ecological principle that only approximately $10\%$ of energy is passed from one trophic level to the next in a food chain.

Restriction Enzyme

An enzyme used in genetic engineering to cut DNA molecules at specific recognition sites.

DNA Ligase

An enzyme used in genetic engineering to join separate fragments of DNA together.

Vector

A carrier (such as a bacterial plasmid or a virus) used to introduce foreign recombinant DNA into a host cell.

Transgenic

An organism that contains genetic material transferred from a different species.

Allele

An alternative form of a specific gene that codes for different variations of an inherited characteristic.

Dominant Allele

An allele that is always expressed in the phenotype when present, even in heterozygous individuals.

Recessive Allele

An allele that is only expressed in the phenotype when both inherited copies are identical (homozygous).

Homozygous

Having two identical alleles for a particular gene (such as $BB$ or $bb$).

Heterozygous

Having two different alleles for a particular gene (such as $Bb$).

Phenotype

The observable physical and physiological characteristics of an organism resulting from its genotype and environmental factors.

Genotype

The specific genetic makeup or combination of alleles possessed by an organism for a gene.

Natural Selection

The mechanism of evolution in which organisms with advantageous inherited traits are more likely to survive, reproduce, and pass those favorable alleles to offspring.