Mitochondria are the primary metabolizing organelles in both plant and animal cells. They break down sugars into energy molecules that power the rest of the cell. Bean-shaped organelles with lots of inner membranes, they are rarer in plants than in animals and occur more frequently in high-energy tissues such as muscles. Mitochondria, like a lot of organelles, are thought to have originated as a separate cell that invaded and was captured to become a part of a larger cell.
There are usually several mitochondria in each cell; some go to each daughter cell when the cell divides. Mitochondria have their own DNA and divide on their own schedule. Plants have an extra metabolizing organelle: the chloroplast. This organelle contains chlorophyll and helps convert sunlight into energy.
All waste produced by a cell must be removed. The vacuoles are small cells-within-a-cell that have surrounding membranes identical to the cell membrane. To eject material from the cell, a vacuole moves to the cell wall and fuses its membrane with the cell membrane. The vacuole's contents then moves outside the cell. Vacuoles can also act as storage sites or as a transport mechanism for neurotransmitters.
In plants, vacuoles are few and large for storage; they are smaller and rarer in animals. The lysosome is a type of vacuole common in animals but rare in plants. It breaks down large molecules and recycles old cell parts.
The nucleus--also thought to have been a captured invader from long ago--contains the information for cell operation in the form of instructions for building proteins. Messengers from the nucleus take the information out of the nucleus one gene at a time. The message goes through an organelle called the endoplasmic reticulum to another organelle called the ribosome.
Cells assemble proteins in the ribosome; newly built proteins assemble into more complex molecules in the endoplasmic reticulum. These protein-building organelles exist in both plants and animals; the process is the same in each.