THE CELL

Cells are the Starting Point

All living organisms on Earth are divided into cells. The main 

concept ofcell theory is that cells are the basic structural unit 

for all organisms. Cells are small compartments that hold the

 biological equipment necessary to keep an organism alive and 

successful. Living things may be single-celled or they may be

 very complex such as a human being.

There are smaller pieces that make up cells such as macromolecules andorganelles. A protein is an example of

 a macromolecule while amitochondrion is an example of an 

organelle. Cells can also connect to form larger structures. 

They might group together to form the tissues of the stomach 

and eventually the entire digestive system. However, in the 

same way that atoms are the basic unit when you study matter,

 cells are the basic unit for biology and organisms.

In larger organisms, the main purpose of a cell is to organize. 

Cells hold a variety of pieces and each cell type has a different

 purpose. By dividing responsibilities among different groups of

 cells, it is easier for an organism to survive and grow.

If you were only made of one cell, you would be very limited.

 You don't find single cells that are as large as a cow. Cells have

 problems functioning when they get too big. Also, if you were

 only one cell you couldn't have anervous system, no muscles

 for movement, and using the internet would be out of the 

question. The trillions of cells in your body make your way of 

life possible.

One Name, Many Types

There are many types of cells. In biology class, you will usually

 work withplant-like cells and animal-like cells. We say 

"animal-like" because an animal type of cell could be anything 

from a tiny microorganism to a nerve cell in your brain. Biology 

classes often take out a microscope and look at single-celled 

microbes from pond water. You might see hydra, 

amoebas, or euglena. 

Plant cells are easier to identify because they have a protective 

structure called a cell wall made of cellulose. Plants have the 

wall; animals do not. Plants also have organelles such as the 

green chloroplast or large, water-filled vacuoles. Chloroplasts 

are the key structure in the process ofphotosynthesis.

Cells are unique to each type of organism. If you look at very 

simple organisms, you will discover cells that have no defined 

nucleus (prokaryotes) and other cells that have hundreds of 

nuclei (multinucleated).

Humans have hundreds of different cell types. You have red 

blood cells that are used to carry oxygen (O2) through the body 

and other cells specific to your heart muscle. Even though cells 

can be very different, they are basically compartments 

surrounded by some type of membrane. 

• Overview
• Cell Membrane
• Memb. Proteins
• Cell Walls
• Connections
• Cytoplasm
• Nucleus
• Chromosomes
• Centrioles
• Ribosomes
• Mitochondria
• Chloroplasts
• Endo. Reticulum
• Golgi Complex
• Vacuoles
• Microfilaments
• Microtubules
• Lysosomes
• Peroxisomes
  

---

Inside the Cell (Canadian Museum of Nature Video)

---