What is a cell?

The Cell Theory says All living things are made of cells Cells are the basic unit of structure AND function in all living things. New cells come from pre-existing cells

Cells come in all shapes and sizes!

There are two types of cells. Prokaryotic Eukaryotic

In the eukaryotic circle add: “Plants, animals, protists and fungi!” In the prokaryotic circle add “Bacteria”

Prokaryotic Cells The simplest type of cells Most likely the first type of cells that formed on Earth All prokaryotic cells have: a cell membrane surrounding the cell cytoplasm where all of the metabolic processes happen ribosomes that make proteins a circular DNA molecule called a nucleoid where the genetic information is held. Most have a rigid cell wall that is used for protection. All prokaryotic organisms are unicellular, bacteria!!

Prokaryotic organisms are asexual Most reproduce through a process called binary fission where basically the cell splits in half after copying its DNA. This means that, without mutations within the DNA, offspring are identical to their parent. Binary fission 15 seconds

Types of Prokaryotic Cells Archaebacteria Cell walls DO NOT contain peptidoglycan. Typically live in extreme conditions. Ex. Extreme temperatures, pH or salt conditions. “Ancient bacteria” Oldest organisms alive. Are believed by many scientists to be one of the first organisms to have lived on Earth when life was first forming. Eubacteria Cell walls contain Peptidoglycan. The type that live inside us and in the soil. They type we can get sick from!

Eukaryotic Cells There are many more organelles within eukaryotic cells. In addition to most of the organelles in prokaryotic cells Eukaryotic cells have many more! a nucleus to house the DNA a nucleolus where ribosomes are made rough endoplasmic reticulum for protein assembly smooth endoplasmic reticulum for making lipids Golgi apparatus for sorting and exporting proteins mitochondria for creating energy a cytoskeleton for structure and transporting information vesicles to move proteins around the cell. centrioles for splitting the cell during mitosis. Cell walls can also be found surrounding some types of eukaryotic cells.

Most eukaryotic organisms are multicellular. This allows the eukaryotic cells within the organism to become specialized through a process called differentiation. Stem cells take on characteristics and job functions that work with other types of cells to create an entire organism. There are a few unicellular eukaryotes as well.  

Depending on the organism's complexity Eukaryotes may use either asexual or sexual reproduction Sexual reproduction allows more diversity in offspring and population by mixing the genes of the parents to form a new combination and hopefully a more favorable adaptation for the environment.

Endosymbiotic Theory Since prokaryotic cells are simpler than eukaryotic cells, it is thought they came into existence first. The currently accepted theory of cell evolution is called the Endosymbiotic Theory. It asserts that some of the organelles, namely the mitochondria and chloroplast, were originally smaller prokaryotic cells engulfed by larger prokaryotic cells.

Endosymbiotic Theory Endosymbiotic Theory 5.32 minutes