Cells and the Cell Cycle

 

The Cell Theory

Objectives for today:
*Understand that all living things are made of cells
*Identify the parts of a cell.
* Understand the difference between plant and animal cells.

 

Cells: The Building Blocks of Life

 

 

  The Cell Theory
1. All living things are made of cells.
2. Cells are the basic units of life.
3. Cells come only from other cells.		 Types of Cells
* Prokaryotes - cells with no nucleus or organells with membranes.
*Bacteria and blue-green bacteria are prokaryotic cells.
* Eukaryotes - cells that contain a nucleus and organelles surrounded by a membrane.
*The cells of protozoa, algae, fungi, plants, and animals are eukaryotic cells. 		 

 

  Protocells:
One theory of the origins of cells states that the first life on earth consisted of several types of tiny protocells, cell-like organisms. These organisms were able to survive and reproduce in a very limited environment because of their simplicity. Over time, some of these protocells came together and shared their specialization in a symbiotic relationship. These colonies of protocells eventually became the cells we know today. 		 

 

Except for bacteria, all organisms we will study this year will be eukaryotes.
Plant cells and animal cells are similar, but do not have exactly the same cell parts and shape.

 

Typical Plant Cell
Typical Animal Cell
Typical Bacterial Cell

 

Cell organells: components of cells with specific functions.

 

 

Cell wall


* On the outside of some cells, mainly bacteria and plants, this structure functions for support and protection.
* There are large pores in the cell wall allowing substances to come in contact with the cell membrane

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* Types of cell walls:


* Primary cell wall - formed during cell growth, it is composed of parallel layers of celluloseand pectin. This structure allows the cell to expand as it grows. While it does provide support, it is not nearly as strong as the secondary cell wall.
* Secondary cell wall - formed after cell growth stops, it is composed of interwoven cellulose and lignin fibers. This structure is very strong, but does not give. It gives plants their "woody" characteristic.
* Cellulose from plants is the major substance composing paper

 

 

Cell membrane


* A complex barrier of lipid molecules separating the cell from its external environment.
* These molecules can move apart to allow larger particles to move in or out of the cell.
 
* The "selectively permeable" cell membrane regulates what passes into and out of the cell. This allows the cell to maintain a "balance" between what is inside the cell and outside.
* Some substances, like water, move freely through the cell membrane by a process known as osmosis.
Answer the following questions. Head your paper Unit 3 Day 1, Cell theory.
1. List the parts of a protocell.
2. What is the difference between plant and animal cells?
3. What does a bacteria cell have that plant and animal cell does not have?
4. List and describe the parts of the cell wall.
5. What does "selectively permable" mean?
6. List the three domains of a protocell.