Prokaryotic and Eukaryotic Cells Video Lecture | Science for Grade 4

On Earth, there are two major types of cells:
prokaryotic and eukaryotic.
Prokaryotic cells are the simplest
and most
ancient types of cells.
They were the only form of life on Earth for billions of years
before eventually giving rise to eukaryotic cells.
If you take a look at prokaryotic and eukaryotic cells side by side,
you can see a number of differences.
To begin with, prokaryotic cells are a lot smaller than eukaryotic cells
and have a simpler structure.
But bear in mind that this simple structure is actually a good thing for prokaryotes,
because it allows them to reproduce very quickly and very effectively.
If you were to look inside a prokaryotic cell,
you would probably be surprised at how simple it is.
For example, prokaryotic cells lack a nucleus.
In fact, the name “prokaryote” actually gives you a hint about its structure.
“kary” means “kernel” or “nucleus” and “pro” means before.
So basically, the word “prokaryote” means “before nucleus.”
The inside of the prokaryotic cell is basically an open unit with no compartments.
There are no membrane-bound organelles.
However, small structures called ribosomes are scattered throughout its cytoplasm.
The cell’s DNA is located in a region of the cytoplasm called the nucleoid region.
The nucleoid region is not the same thing as a nucleus
because it’s not enclosed by a membrane.
Prokaryotes also have a cell wall that surrounds the plasma membrane.
The composition of the cell wall depends on whether the cell is an archaean or a bacteria,
but basically it consists of complex polysaccharides.
Prokaryotes also often possess one or more flagella,
which are used for movement.
In contrast, eukaryotic cells contain a membrane-bound nucleus
and other membrane-bound organelles.
The name “eukaryote” also gives a hint about its structure.
“eu” means true- and remember that “kary” means nucleus,
so in essence the word “eukaryote” means “true nucleus.”
Eukaryotic cells are larger and much more complicated than prokaryotic cells.
However, they do share a few things in common with prokaryotes.
Let’s take a look at a Venn Diagram to compare prokaryotes to eukaryotes,
and to also see what areas they have in common.
Let’s start with their commonalities:
Both prokaryotes and eukaryotes:
• Have DNA as their genetic material
• Have ribosomes
• Have cytoplasm
• Have a plasma membrane
Now let’s look at some of the ways they differ:
• Prokaryotic cells are the oldest type of cell.
They are small and relatively simple.
Eukaryotic cells evolved from prokaryotic cells later.
They are larger and much more complex internally.
• Prokaryotes lack both a nucleus and membrane-bound organelles.
Eukaryotic cells have a nucleus, and also contain organelles.
• Prokaryotes are single-celled organisms.
Eukaryotes can be either single-celled or multicellular.
• And finally, the DNA of a prokaryote
is usually organized as a single, circular chromosome,
while the DNA of a eukaryote is organized as linear chromosomes.