Organisms are composed of cells, the smallest units of living matter. Cells are capable of self-reproduction, and existing cells come only from preexisting cells. Cells are very small and are measured in micrometers.” (Audersirk,1999).The plasma membrane regulates exchange of materials between the cell and the external environment. Cells must remain small in order to have an adequate amount of surface area per cell volume.
Eukaryotic cells make up organisms from the Protist, Fungi, Plant, and Animal Kingdoms.
These are cells with a nucleus; this is where the genetic material is surrounded by a membrane much like the cells membrane. Eukaryotic cells are found in humans and other multicellular organisms (plants and animals) also algae, protazoa. They have both a cellular membrane and a nuclear membrane, also the genetic material forms multiple chromosomes that is linear and complexed with proteins that help it 'pack' and is involved in regulation (Kun, 2000).
Eukaryotes = Have nucleus + organelles Size ranges 10-100 micrometers
“Organelles are intracellular structures that perform specific functions in cells similar to that of organs in the body, and are structurally more complex due to the use of internal membrane. Organelles of the endomembrane system include: nucleus, smooth and rough endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles” (Fried, 1990)
Plants vary from animal cells in that they have large vacuoles, cell wall, chloroplasts, and a lack of lysosomes, centrioles, pseudopods, and flagella or cilia. Animal cells do not have the chloroplasts, and may or may not have cilia, pseudopods or flagella, depending on the type of cell.
The fluid inside this double-membrane organelle is called the stroma. The stroma is, according to the endosymbiont theory, the cytoplasm of the prokaryotic endosymbiont. Floating in the stroma are tiny membrane sacs. These are called thylakoids. The sacs are stacked in groups. Each group is called a granum.
