Eurkaryotes are distinguished by the possession of organelles, which are discrete internal structures surrounded by and in many cases made up of phospholipid and protein membranes. The organelles listed below occur exclusively but not universally in eukaryotes.

Introconversion Organelles
Endoplasmic reticulum, the Golgi apparatus, lysosomes, peroxisomes, the plasma membrane, and the nuclear membrane are all composed of the same phospholipid bilayers. These are referred to as the Interconversion Organelles, because they can convert into one another.

Endoplasmic Reticulum (ER) – a system of internal membranes within the cell, which divides the interior of the cell into compartments; on the surface of the ER, the cell manufactures carbohydrates and lipids.

Part of the ER is covered with protein-making ribosomes – this is called rough ER. The proteins made here, such as enzymes, are intended for export from the cell. Smooth ER does not have ribosomes on its surface, and is involved in fat metabolism and the detoxification of toxic substances (such as alcohol and drugs) found in the liver.

Golgi Apparatus ? composed of 5 to 20 flattened, smooth, membranous sacs that resemble a stack of pancakes. Here, certain molecules produced in the cell such as mucus, carbohydrates, glycoporteins, and insulin are concentrated and packaged into vesicles for transport.

Lysosomes – vesicles containing enzymes which break down macromolecules; they digest worn-out cell components to make way for newly formed ones and they eliminate unwanted particles the cell has taken in.

Lysosomes are used in cells in 4 major ways:

Peroxisomes – self-assembling enzyme-rich organelles that destroy toxins and also participate in the breakdown of metabolic products.

Nuclear Membrane/ Nucleus – this membrane-encased structure contains the genetic material of the cell. The nuclear membrane has pores, called nucleopores, which allow for the passage of RNA. Nuclear components within the membrane are:

Energy Producing Organelles
Two eukaryotic organelles, mitochondria and chloroplasts, are distinct from the other organelles. These structures have different types of membranes as well as their own DNA.

Mitochondria ? a double-membrane bound organelle that extracts energy from organic molecules (food); the site of cell metabolism. The inner membrane is bent into numerous folds called cristae; the cristae separate the mitochondrion into two compartments, an inner matrix and an outer compartment.

Chloroplasts ? saclike organelles that contain chlorophyll, a green pigment that carries out photosynthesis. Chloroplasts contain thylakoid membranes, which contain concentrated chlorophyll. The thylakoid membranes stack up and make up stacks called grana or granum. The space between the grana is known as the stroma. Photosynthesis produces sugars which are used as an energy source for cells.