Animal cell organelles

Cell organelles are the structures within a cell. They are a bit like the organs in a human body. They each have a specific role to play and have a distinctive shape and size.


•	Inside the cell
•	Heredity and reproduction

In this section:

Cell Membrane - The cell membrane encloses the cell contents. Its main function is to control what gets into and out of the cell.

Cytoplasm - The cytoplasm contains primarily water and protein material. This is where the other cell organelles reside, and where most of the cellular activities take place.

Nucleus - The nucleus generally contains the genetic material for the cell. Because it contains the DNA and chromosomes, which affect the proteins that determine the activities of the cell, the nucleus can be considered to be the cell's control centre.

Ribosomes - Ribosomes are where protein synthesis takes place. Some are attached to the rough endoplasmic reticulum, and some are free in the cytoplasm.

Lysosomes - Lysosomes are membrane-bound sacs of enzymes. In a controlled and specific way, they breakdown old or unneeded parts of the cell into small organic molecules that can be reused.

Animal cell.

Mitochondria - Mitochondria are large organelles where oxygen is combined with food to produce ATP (adenosine triphosphate), the primary energy source for the cell. Mitochondria contain their own DNA, RNA and ribosomes, and can reproduce themselves independently of the cell in which they are found.

Endoplasmic Reticulum (ER) - The endoplasmic reticulum is a series of interconnecting flattened tubular tunnels. There are two sorts of endoplasmic reticulum - rough ER and smooth ER. The rough ER has lots of attached ribosomes. The smooth ER has no attached ribosomes and so looks 'smooth'. The rough ER takes in the proteins made on the ribosomes so that they cannot escape into the cytoplasm. The smooth ER is not involved in protein synthesis, but has other functions.

Most of the proteins leaving the endoplasmic reticulum require further processing in the Golgi apparatus, before they are ready to perform functions within or outside the cell.

Golgi Apparatus - The Golgi apparatus is composed of small membranous sacs, and is associated with the endoplasmic reticulum (ER). Though its function is still not entirely understood, it seems that proteins from the ER travel to the Golgi apparatus, where they are transformed and packaged into sacs before being moved to their final destination.

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