Prokaryote Cells - A Closer Look

A Closer Look

We know from looking at cells that they are made up of organelles. These organelles have a specific function depending on the type of organism. They work with other organelles to help maintain the cell, reproduce the cell, allow for transfer of nutrients, and so on. Prokaryotes do not have organelles as such, however they do have components that work similarly.

The components within a prokaryotic cell include:

• nucleoid
• pili
• ribosomes
• food granule
• flagellum
• mesosome
• plasmid (DNA)
• cytoplasm
• plasma membrane
• cell wall
• capsule/slime layer

Interesting fact: prokaryotic cells are the oldest class of organisms that live and have lived on Earth. They are some 4 billion years old, and along with Archaea make up 70% of the world's living organisms.

Nucleoid

A nucleoid is similar to a nucleus of a eukaryote cell. It contains some DNA information such as the type of bacteria or other organism that it is. It is a compacted set of copied DNA in a continuous thread, with the addition of RNA and proteins. Where the chromosome in a eukaryote cell is typically an X-shape, the chromosome in a prokaryote is sometimes spread through the rest of the cell in any format.

The function of the DNA is to help with reproduction and the activity of the cell in general. Inside the nucleoid there are enzymes that help with the process of replication of DNA to create new cells, and they also help with regulating the size or the amount of genetic material within the cell.

Pili

Pili, or a singular Pilus, are hair-like structures that surround the prokaryote. They act to help with movement, as well as allow for the transport of nutrients and DNA material from other cells. Indeed, if there are three different types of bacteria on a petri dish, for example, you would eventually see them link up together. When they do, they pass on DNA information and nutrients between them through the pili.

They are also attributed to adhesion to surfaces. This is where infection and disease can spread, due to the fact that [in the example of someone having some on their hands] they can be placed on multiple surfaces through the sense of touch and are left there if not cleaned.

Ribosomes

So, like a eukaryote cell, prokaryotes also have ribosomes. They work in a similar fashion as well, by creating protein. Their genetic makeup is 35% protein, and 65% ribosomal RNA. They work to translate mRNA (messenger RNA) into proteins.

In modern medicine, and particularly with bacteria, scientists use the ribosome RNA data to figure out how to make medications that will combat them or prevent them from being infectious.

Food Granule

Food granules are stored in the cell at random periods of time, so as to help with providing the cell with food as and when needed. They are just floating within the cell and are used by the other organelles when needed. In eukaryotes they are also called vesicles.

Flagellum

MAde of it's own proteins, a flagellum is a tail-like structure that are used to move the cell around it's own biome. They don't have any other purpose, but might work in a similar fashion to the pili.

Mesosome

Situated at the cell wall, a mesosome acts to help in the respiration of the cell. It is coiled in shape, and is attached directly to the cell wall inside the cell itself.

Plasmid (DNA)

A plasmid is a single DNA gene stored within a circular component of the bacterial cell. It's function is to help the organism fight off other organisms - it does this by producing toxins to deter the intruder, or by enhancing the cell somehow to stop it from happening full stop.

Cytosplasm

As a prokaryote doesn't have a nucleus, and instead uses the nucleoid as a rather messy thread like structure, there is no need for cytosol in a cell. Instead, they each have cytoplasm, which is also in a eukaryote cell. This forms up the rest of the cell that is not taken up by the other components within.

Plasma Membrane

This is part of the entire capsule and cell wall, and is a lipo-proteinous plasma membrane that helps with the cell wall.

Cell Wall

A thin membrane that holds everything in the cell, the cell wall is literally that. It is semi permeable, allowing nutrients needed to get in, but keep the other organelles in as they are larger.

Capsule/Slime Layer

A thick coat surrounding the cell, the capsule enables the cell to withstand some external injuries from happening. These capsule covered prokaryotes are contagious bacteria (such as Diplococcus pnemoniae, which is commonly called pneumonia).

Here is a YouTube video from sci-ology on the structure of the prokaryotic cell: