Lysosomes

Lysosomes are organelles found in all animal cells¹ and less commonly found in plant cells², that consist of hydrolytic digestive enzymes enclosed by a single-layer membrane (vesicle)¹.

Their purpose is to break down substances that are harmful or no longer useful for the cell¹, or even entire organelles³, and recycle their components for later use by the cell¹.Lysosymes are present in greater numbers in white blood cells, since they are needed to break down toxic substances and bacteria that have been taken in by endocytosis¹. 

The hydrolytic enzymes found within the lysosomes are all produced in the rough endoplasmic reticulum (rER) and transported to the Golgi apparatus for modification¹. They are then released from the Golgi apparatus inside vesicles¹.

References:

1) Davidson M.W., Florida State University, 1995. Cited: 24/11/2016 (Available from: https://micro.magnet.fsu.edu/cells/lysosomes/lysosomes.html)                    

2) Sullivan J.A., CELLS Alive!, 1994. Cited: 24/11/2016 (Available from: http://www.cellsalive.com/cells/cell_model.htm)                     

3) Alberts B., Johnson A., Lewis J., Morgan D., Raff M., Roberts K., Walter P., ‘Molecular Biology of the Cell’, 6th Edition, New York: Garland Science, Taylor & Francis Group. 2015. Page 642.