Introduction to Prokaryotic Cells | A-level Biology | OCR, AQA, Edexcel

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The key points of this video include:

1. Universal Features of Prokaryotic Cells
2. The Prokaryotic Cell Wall
3. Non-Universal Features of Prokaryotes
4. Pili
5. Mesosomes

Universal Features of Prokaryotic Cells

Prokaryotic cells are the most common type of cell on earth - there are more bacterial cells in your own body than human cells. They are small cells that have some features in common with eukaryotic cells. They include all of the bacteria, as well as another cell type called archaea. Prokaryotes have features common to all cells, such as cytoplasm and a cell membrane. They also have ribosomes for translating protein. Prokaryotes store their energy as glycogen granules and oil droplets.

The Prokaryotic Cell Wall

Prokaryotes have a cell wall lying just outside the membrane. Unlike plant cells, the prokaryotic cell wall is made of murein (or peptidoglycan) not cellulose. Murein (or peptidoglycan) is a polymer made up of polypeptides and polysaccharides. The prokaryotic cell wall protects the prokaryote from mechanical forces and water potential changes. The cell wall needs to be broken down during cell division. This is co-ordinated by the simple prokaryotic cytoskeleton.

Non-Universal Features of Prokaryotes

The following features of prokaryotic cells are only found in some species, not all. Some prokaryotes have a tail-like structure called a flagellum. They look like the tail of a human sperm - but they have different chemical structures. Some prokaryotes have a waxy capsule that lies outside of the cell wall. This protects the prokaryotes from being detected by other cells. It also allows them to stick together.

Pili

Pili also help stick bacteria together. They are hair-like projections made of protein that extend out of the bacteria.

Mesosomes

Mesosomes are infoldings of the prokaryotic cell membrane. They carry out aerobic respiration - having a similar role to the mitochondrial cristae.
Summary

Prokaryotic cells have features in common with eukaryotes, for instance, the cell membrane, the cytoplasm, a cell wall, and ribosomes
Prokaryotes also have a simple cytoskeleton
Prokaryotes have small ribosomes and a cell wall made of murein/peptidoglycan
Some prokaryotes have a capsule, pili, and a flagellum
Some prokaryotes also have mesosomes which are involved in aerobic respiration

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