Glossary

An A-Z of keywords and phrases, all of which are relevant to the post-16 biology curriculum.

 

A B C D E F G H I J K L M N O P Q R S T U V W Y Z
Obesity

A condition in which a person is very overweight, with a high proportion of body fat. Obesity has been linked to many health problems.

Obligate anaerobes

Organisms that are killed in the presence of oxygen in its concentration on Earth, which is approximately 21 per cent of the atmosphere. They are ‘obligated’ not to have oxygen and live in environments without it, such as deep-sea hydrothermal vents.

Obligate parasite

An organism that can only complete its life cycle by parasitically using a host.

Occipital lobe

The part of the brain that manages vision, containing dozens of areas that are specialised for processing inputs from the eyes.

Ocean conveyor/thermohaline circulation/meridional overturning circulation

Global-scale ocean currents – including the Gulf Stream, which keeps the UK’s climate relatively mild. Although some have suggested these currents could disappear as a result of climate change, drastically lowering temperatures in the UK, this is currently thought to be unlikely.

OILRIG

A mnemonic for redox reactions – oxidation is loss (of electrons or hydrogen), reduction is gain (of electrons or hydrogen).

Olfactory bulb

A neural structure in the forebrain involved in the sense of smell.

Omnivore

An individual (animal or human) who eats animals (prey) as well as plants.

Oncology

The branch of medicine that deals with cancer, including diagnosis, therapy, care and screening.

Oocyte

An immature (undeveloped) female sex cell (egg).

Opioids

Compounds that are chemically similar to opium, and are often used as pain-relief medication.

Organ

A group of tissues that act together to perform a function.

Organelles

Intracellular structures that have a specialised function, for example chloroplasts and mitochondria.

Organoid

A cell/tissue culture method that aims to mimic organ structure and function in vitro.

Osmosis

The movement of water from an area of high water concentration to an area of low water concentration (ie with a concentration gradient), across a partially permeable membrane. This process does not require energy.

Osteoporosis

A disease in which the bones are weakened, as old bone is broken down by the body at a faster rate than new bone is created. The risk of osteoporosis increases with age, but it can also be caused by vitamin D deficiency and other medical conditions.

Oxidation

The loss of electrons or hydrogen (called dehydrogenation), or the gain of oxygen by a molecule, atom or ion.

Oxidative phosphorylation

A process in which mitochondria make ATP using the energy released when electrons are transported from reduced NAD and FAD to oxygen in the electron transport chain of cellular respiration.

Oxyhaemoglobin

The substance formed when haemoglobin has bound to oxygen in the blood.