Definitions and Concepts for Edexcel Biology IGCSE

A collection of vocabulary terms and their definitions related to the IGCSE Biology topic on the nature and variety of living organisms.

Amoeba

Protoctists that live in pond water and resemble animal cells.

Cell

The basic building block of all living organisms.

Cell membrane

A partially permeable barrier that surrounds the cell.

Cell wall

An outer, structural layer that surrounds some cells; in plant cells, it is made of cellulose, and in fungi, it is made of chitin.

Chlorella

A protoctist that has features similar to plant cells, e.g., chloroplasts.

Chloroplast

An organelle which is the site of photosynthesis.

DNA

A double-stranded polymer wound to form a double helix that carries the genetic code.

Eukaryotic cell

A type of cell found in plants and animals that contains a nucleus.

Human Immunodeficiency Virus (HIV)

An infectious virus that weakens the immune system and can lead to AIDS.

Hyphae

Long filaments of a fungus that contain many nuclei.

Influenza virus

An infection virus that causes influenza (the flu).

Lactobacillus bulgaricus

A rod-shaped species of bacterium used to produce yoghurt from milk.

Mucor

A multicellular fungus that has a hyphal structure.

Mycelium

A collection of thread-like hyphae in a fungus.

Pathogens

Microorganisms that cause infectious disease.

Photosynthesis

An endothermic reaction in which energy is transferred from the environment to the chloroplasts by light.

Plasmids

Loops of DNA found in the cytoplasm of prokaryotic cells.

Plasmodium

Pathogenic protoctists that cause malaria.

Pneumococcus

A spherical, pathogenic bacterium that causes pneumonia.

Prokaryotic cell

A type of cell found in bacteria that does not contain a nucleus.

Protoctists

Microscopic single-celled organisms.

Saprotrophic nutrition

The mode of extracellular nutrition in which digestive enzymes are secreted onto the food outside the cell and the products of digestion are absorbed.

Tobacco Mosaic Virus (TMV)

A widespread plant pathogen affecting many species of plants, which produces a mosaic pattern on the leaves and infects chloroplasts.

Virus

A non-living organism that can only reproduce inside host cells, possessing a protein coat containing nucleic acids.

Yeast

A single-celled fungus.