ABSTRACT
Eukaryotic cells have a membrane-bound nucleus and a number of other membrane-bound subcellular organelles, each of which has a specific function. The plasma membrane surrounds the cell, separating it from the external environment. The plasma membrane is a selectively permeable barrier due to the presence of specific transport proteins. It is also involved in receiving information when ligands bind to receptor proteins on its surface, and in the processes of exocytosis and endocytosis. The nucleus stores the cell's genetic information as DNA in chromosomes. It is bounded by a double membrane but pores in this membrane allow molecules to move in and out of the nucleus. The nucleolus within the nucleus is the site of ribosomal ribonucleic acid synthesis. The Golgi apparatus, a system of flattened membrane-bound sacs, is the sorting and packaging center of the cell. Peroxisomes contain enzymes involved in the breakdown of amino acids and fatty acids, a byproduct of which is hydrogen peroxide.
