OCR GCSE Biology A Key Terms

The real-life, physical size of the biological specimen.

An exothermic reaction that requires oxygen to break down glucose and release energy for the cell.

Artifacts caused by poor slide preparation, identifiable by their perfectly circular shape and thick black edges, which do not contain cellular structures.

A structural feature or distortion seen in a microscopy image that is not naturally present in the specimen, caused by harsh preparation techniques.

The molecule used as the cell's energy currency to store the energy released during cellular respiration.

The process by which cells sense their environment and respond to signals using receptor molecules on their membrane.

A partially permeable boundary that surrounds the cell, controlling the movement of substances in and out.

A solution of sugars and salts stored inside the permanent vacuole of a plant cell.

The complex carbohydrate that provides structural strength in plant cell walls.

A rigid outer layer that provides structural support and prevents the cell from bursting; made of cellulose in plants and peptidoglycan in bacteria.

The green pigment found in chloroplasts that absorbs light energy required for photosynthesis.

Organelles found in plant cells where photosynthesis occurs, containing complex internal membrane structures.

Tightly coiled, linear structures of organized DNA found inside the nucleus of eukaryotic cells.

When a signaling molecule specifically matches and fits into the unique structure of a receptor molecule.

The difference in light intensity or colour between the specimen and the background that makes the object distinguishable.

A small, thin square of glass or plastic placed over the specimen to keep it flat and protect the objective lens.

The inner membrane folds of mitochondria, first clearly observed using electron microscopy.

A gel-like substance inside the cell where most metabolic chemical reactions take place.

A polymer made of repeating nucleotides that contains the genetic instructions to code for all required proteins.

Biological catalysts made of protein that control chemical reactions within cells.

A complex cell, typically 10–100 µm, that contains a nucleus and membrane-bound organelles.

Tail-like structures on some prokaryotic cells that rotate to propel the cell through liquids.

Stacks of thylakoids found inside chloroplasts.

The size of the specimen as it appears in a drawing or printed photograph, usually measured with a ruler in millimetres.

A stain used for plant cells that reacts with starch to turn blue-black and tints other cell components brown.

The number of times larger an image is compared to the actual size of the object or specimen.

A transcript of the DNA code that travels from the nucleus to the ribosomes in the cytoplasm.

A stain commonly used on animal cells that binds to nucleic acids, making the nucleus appear dark blue.

Organelles where aerobic respiration occurs, revealed by electron microscopy to have an inner folded structure.

The monomer units of DNA, consisting of a sugar, a phosphate group, and a base.