Phloem contains tubes called sieve tubes that are made from cells called sieve tube elements.

Any molecule which the body recognises as foreign is an antigen.

Atrial systole is the stage of the cardiac cycle when the muscle in the walls of the atria contracts.

Codominant alleles each affect phenotype when both of them are present.

Increasing the substrate concentration may stop the the works of competitive inhibitor.

The Okazaki fragments are formed the parent strand that runs in the 5′ to 3′ direction.

Oxygen diffuses down its concentration gradient from the air in the alveoli to the blood, and carbon dioxide diffuses down its concentration gradient in the opposite direction.

Osmoregulation is the control of the water potential of blood and tissue fluid by controlling the water content and/or the concentration of ions, particularly sodium ions.

Glycosidic bond: a C–O–C link between two sugar molecules, formed by a condensation reaction; it is a covalent bond.

Node of Ranvier is a very short gap between Schwann cells where myelinated axons are not covered in myelin so are exposed to tissue fluid.

Glycolysis is the splitting, or lysis, of glucose. It takes place in the cytoplasm of a cell.

Antibiotic resistance arises by mutation and becomes widespread when antibiotics are overused.

The cells in your body vary in size from about 5 μm to 40 μm.