Cholera toxin is a protein secreted by the bacterium Vibrio cholerae and responsible for the main symptom of cholera, an acute diarrhoea.

The Tapada Nacional de Mafra, or simply Tapada de Mafra, is a preserved forest area located in Sobral da Abelheira, in the village of Mafra, in the district of Lisbon, that has about 1187 hectares, and where multiple species of natural fauna and flora can be found. The Tapada de Mafra was first created in […]

Tissue concept The term tissue designates a set of cells having essentially the same structure and function. Tissues juxtapose, interpenetrate, and combine to form organs.   Tissue formation All cells originate in the embryo and differentiate themselves through several cellular processes to form a tissue. These cellular processes are: direction and number of cell divisions, […]

Turtles are reptiles with a protective shell and a beak-shaped, curved and hard mouth. Besides providing protection against predators, aggressions or adverse weather conditions, the shell also provides the animal with camouflage – because of its colours, shape and texture, it usually resembles elements from the surrounding environment (such as leaves or rocks). Some species […]