Cell and Cell Theory

Cell theory

The cell theory developed in 1839 by microbiologists Schleiden and Schwann describes the properties of cells. It is an explanation of the relationship between cells and living things. The cell theory states :

1. All living thighs are made of cells and their products

2. New cells are created by old cells dividing into two

3. Cells Are the basic building blocks of life

The cell theory is applicable to all living things, however big or small. The modern understanding of cell theory extends the concepts of the original cell theory to include the following:

1. The activity of an organism depends on the total activity independent of cells.

2. Energy flow occurs in cells through the breakdown of carbohydrates by respiration

3. Cells contain the information necessary for the creation of new cells. This information is known as the hereditary information and is contained within DNA

4. The contents of cells from similar species are basically the same

Eukaryotic Cells:

1. They have membrane bound structures called cell organelles

2. Eukaryotic Cells includes cell of fungi, animals, protists and plants

3. These cells are more specialized than prokaryotes

Prokaryotic Cells:

1. The cells are usually smaller and simpler than prokaryotic

2. Prokaryotic cells do not have membrane bound structures

3. The DNA or genetic material, forms a single large circle  that coils up on itself

4. Prokaryotic cells  belong to the domain of Bacteria or Archaea.

Organelles  in the Cytoplasm:

A cell is like a factory. Just as a factory is made up of many people and machines, a cell has many different parts, each with a special role. The different parts of the cell are called organelles, which means "small organs." All organelles are found in eukaryotic cells, but most are NOT found in prokaryotic cells. Pay attention to which ones are included in prokaryotic cells.

Below are the main organelles found in cells:

1. The nucleus of a cell is like a safe containing the factory’s trade secrets, including information about how to build thousands of proteins.

2. The mitochondria are powerhouses that create ATP (adenosine triphosphate), which provides the energy needed to power chemical reactions. Plant cells have special organelles called chloroplasts that capture energy from the sun and store it in the bonds of sugar molecules, using a process called photosynthesis 

3. The vacuoles are like storage centers. Plant cells have larger ones than animal cells because they need to store water and other nutrients.

4. The lysosomes are like the recycling trucks that carry waste away from the factory. Inside lysosomes are enzymes that break down old molecules into parts that can be recycled into new ones.

5. Eukaryotic cells also contain a skeleton-like structure called the cytoskeleton. Like our bony skeleton, a cell’s cytoskeleton gives the cell its shape and helps the cell to move. 

6. In both eukaryotes and prokaryotes, ribosomes are where proteins are made. Ribosomes are like the machines in the factory that produce the factory’s main product. Proteins are the main product of the cell.

7. Some ribosomes can be found on folded membranes called the endoplasmic reticulum (ER). If the ER is covered with ribosomes, it looks bumpy and is called rough endoplasmic reticulum. If the ER does not contain ribosomes, it is smooth and called the smooth endoplasmic reticulum. Proteins are made on the rough ER. Lipids are made on the smooth ER.

8. The Golgi apparatus works like a mailroom. The Golgi apparatus receives the proteins from the rough ER,