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If this grapefruit represented the nucleus, the skin would be the nuclear membrane, the red section would be the nuclear cytoplasm, and the center hole would be the nucleolus.Nucleus image by Yuriy Rozanov from Fotolia.com
Start with the organelle in the center of the cell, the nucleus. This structure is surrounded by a nuclear membrane with pores, and is where the DNA of the cell is housed, usually wrapped up with proteins (chromatin). In the center of the nucleus is the nucleolus, depicted as a ball floating in the cytoplasm that is in the nucleus. Here the DNA is transcribed into messenger RNA (mRNA); this mRNA is what exits the nucleus to carry out the genetic message of the cell. - 2
The ER is depicted as loosely coiling around the nucleus in most drawings.coiled rope image by meesh66 from Fotolia.com
Next move to the snake-like wrappings that surround the nucleus -- the endoplasmic reticulum (ER). There may or may not be bumps on the ER (these bumps are called ribosomes); if it has bumps it is called rough ER, and if it lacks bumps the organelle is called smooth ER. Here is where the mRNA is used to make proteins in a process called translation. - 3
The golgi apparatus is usually depicted as three or four bending cylinders or tubes grouped together.tubes image by Dusan Radivojevic from Fotolia.com
Locate the golgi apparatus, usually depicted as a group of three or four bending cylinders. It is usually located next to the ER and is where the proteins are modified (folded), stored, then shipped out of the cell.
These proteins are carried through the semi-gelatinous substance the organelles float in (cytoplasm) by vacuoles. These vacuoles are pieces of membrane which have bulged off the golgi apparatus and other organelles and form a small enclosed circle to carry their packages into and out of the cell. Vacuoles can be compared to bubbles pinching off in water and carrying oxygen to the surface. Usually vacuoles carry proteins, amino acids, enzymes, etc. - 4
When looking at a centriole, it is usually depicted as a five or more pointed cylinderical structure made up of smaller cylinders.fleurs blanche tropicale image by margouillat photo from Fotolia.com
Identify the other organelles in the cell. The mitochondria (where the cell creates its energy) looks like a sliced-open jelly bean with pieces of its membrane folded inwards. These membrane parts look like stubby fingers reaching inward.
The lysosome and peroxisome organelles look very similar to a vacuole in size and shape, except these organelles store digestive enzymes and acids to destroy invading bacteria or viruses, or to kill the cell (apoptosis). A lysosome will fuse with a vacuole if need be and release its contents on the vacuole's contents, thereby killing anything the vacuole is carrying.
The centriole is an elongated multiple pointed cylinders made up of even smaller cylinders; these are usually easy to spot since the have such a unique shape and are usually grouped in pairs. Centrioles are used to help the cell when it goes through its dividing process (mitosis). - 5
The cell membrane determines what gets in and out of a cell.green cells 3 image by chrisharvey from Fotolia.com
Don't forget the cell membrane--the lipid bilayer that surrounds the cell and keeps the organelles from floating aimlessly throughout the body. The cell membrane is also important because it carries "self" markers on its surface so the immune system can determine if the cell belongs to the body or if it is a foreign substance and needs to be destroyed.
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