GCE O Level Biology: Definitions of Keywords from Nutrition in Humans, Respiration and Excretion

Peristalsis

Rhythmic wave-like contractions of the wall of the gut caused by alternate contractions of the circular and longitudinal muscles in the walls to help push food along the gut

Emulsification of fats

Occurs when bile breaks big blobs of fat into smaller fat droplets

Egestion

Removal of undigested food from the body

Deamination

Process of removing amino groups from excess amino acids and converted to urea, and occurs in the liver

Detoxification

Process of converting harmful substances into harmless substances

Cirrhosis of the liver

Disease where liver cells are destroyed and are replaced with fibrous tissue

Respiration

Oxidation of food substances with the release of energy in living cells

Aerobic respiration

Oxidation of food substances in living cells, in the presence of oxygen, with the release a large amount of energy. Carbon dioxide and water are released as waste products.

Anaerobic respiration

Breakdown of food substances in the absence of oxygen. Less energy is released than aerobic respiration.

Oxygen debt

Amount of oxygen required to oxidise lactic acid produced in muscles during anaerobic respiration

Gaseous exchange

Exchange of gases between an organism and the environment

Inhalation / inspiration

Taking in of air

Exhalation / expiration

Giving out of air

Cancer

An uncontrolled division of cells producing outgrowths or lumps of tissues

Excretion

Process by which metabolic waste products and toxic materials are removed from the body of an organism

Ultrafiltration

Process in which hydrostatic pressure causes water and small dissolved substances and ions to move across the capillary wall into the nephron tubule

Osmoregulation

Control of water and solute levels in the blood to maintain a constant water potential in the body