Transport system of the body made up of the heart, the blood vessels and the blood. Also known as the circulatory system
Breaking down glucose (food) without oxygen to provide available energy for the cells. The glucose reacts with oxygen to produce energy in the form of ATP with carbon dioxide and water as waste products
Cells which are adapted to carry out a specific function in the body
The organ system in the body which breaks down large insoluble food molecules into small soluble molecules which can be used by the body
Cells that cover the internal and external surfaces of organs
Made up of many cells
Several organs working together to carry out a specific function in the body
The biochemical process by which the cells in the body releases energy
The basic building blocks of proteins. There are twenty amino acids used, in different combinations, to make every protein required by the human body.
An endocrine gland which produces insulin
A type of sugar: a mono saccharide with 6 carbon atoms (a hexose sugar).
A group of cells in an organism that are specialised to work together to carry out a particular function.
A structure with a particular function which is made up of different tissues.
All cells need the same basic things - glucose and oxygen for respiration, amino acids and other food molecules for cell-building and growth, and the removal of poisonous waste products.
In a small, single celled organism such as an amoeba, simple diffusion is enough to supply the needs of the cell. Useful substances can diffuse in from the surroundings and waste products can diffuse out fast enough for the organism to survive successfully.
However, as organisms get bigger the surface area to volume ratio changes. It gets smaller. As a result simple diffusion is no longer enough. There is not a big enough surface area for diffusion to take place over, particularly in active organisms. Food and oxygen cannot reach the cells fast enough to supply cellular respiration. The waste products cannot be removed fast enough to prevent them damaging the cells. A transport system is needed.
The link between size and the surface area:volume ratio