Guest Author - Sarah Meadmore

Cells are the building blocks of all living things: you, me, my dog, your cats, the flies on our ceilings and the cockroaches in our walls. (Shudder). The flowers on our window ledge and the carrots on our plate are also made up of cells. But the cells of plants and animals are different. And this article is about animal cells.

For a diagram of an animal cell, visit http://www.sarahmeadmore.com/2008/07/animal-cell-for-bella-online.html

Within each cell, small structures called organelles have specific functions - just as a whole human has different organs with specific duties.

The Cell Membrane
The essence of an animal cell is the cell membrane which contains the protoplasm . Without the cell membrane, there would be no cell. Just like, without stretchy rubber, there would be no balloon. And that is why I am starting with the cell membrane.

The cell membrane is made of a phospholipids bilayer.

The membrane forms a barrier between the world outside the cell and the inside. Most substances are unable to diffuse through the membrane without help. So, embedded in the membrane are guardian proteins that act as receptors, ion pumps and transportation aides.


Lysosomes
Lysosomes are the intestines of the animal cell. They digest any unwanted material within the cell and the products of that digestion are ejected into the cytosol.


Centriole
These things always come in pairs. They are only in animal cells and are made of short microtubules. They reside just outside the nuclear envelope.


Microtubules
Microtubules are made of the protein tubulin. They aid the transport of materials and organelles within the cell. They are the core of cilia and flagella, and they form the meiotic and mitotic spindles of nuclear division.


Vacuole
Vacuoles have more use in plant cells. They are fluid-filled, membrane-bound cavities.


Nuclear Pore
At a nuclear pore, the inner and outer nuclear membranes have joined and the cytoplasm and the nucleoplasm connect. There are many pores in the nuclear membrane and they allow the passage of macromolecules into and out of the nucleus.


Nuclear Envelope
The nuclear envelope is a double membrane, surrounding the nucleus of eukaryotic cells.


Nucleolus
rRNA is synthesized in the nucleolus.


Chromosomes
Chromosomes carry the genetic information of a cell. They are made of DNA.


Golgi Body
The Golgi Body is a stack of flattened sacs of membrane. It directs membrane lipids and proteins and secretory proteins to their correct destinations.


Mitochondria
These organelles are where energy, in the form of ATP, is generated and where aerobic respiration takes place.


Ribosomes
Ribosomes are found in all cells. They are proteins and it is at these proteins that mRNA is translated and protein synthesis takes place.


Endoplasmic Reticulum
We call the endoplasmic reticulum (ER) rough endoplasmic reticulum, when ribosomes are attached, or smooth endoplasmic reticulum when there are no ribosomes. The ER is important in the synthesis and transport of some proteins and lipids.