Topic 2.2 Prokaryotic Cells

Assessment Statements:

2.2.1 Draw and label a diagram of the ultrastructure of Escherichia coli (E. coli) as an example of a prokaryote

2.2.2 Annotate the diagram from 2.2.1 with the functions of each named structure.

2.2.3 Identify structures from 2.2.1 in electron micrographs of E. coli

2.2.4 State that prokaryotic cells divide by binary fission

Introduction to Prokaryotes

Prokaryotic Cell Structure

Annotate the diagram

Cell Membrane

Controls passage of materials into and out of the cell

All cells have a cell membrane

Cytoplasm

Fluid portion of all cells

Location of cellular metabolism

Ribosomes

Float freely in the cytoplasm of all cells

Smaller in prokaryotes (70s)

The site of protein synthesis.

NucleoidThe glob of DNA in all

prokaryotic cells

Still a double helix

Ends come together to form a circle

Not wrapped around proteins as in eukaryotic cells (termed “naked DNA”).

Prokaryote vs. Eukaryote Chromosome

DNA double helix

Prokaryote

Eukaryote

Plasmid

A small circle of DNA found in some prokaryotes that exists and replicates independently of the main DNA in the nucleoid.

Often contain genetic instructions for resistance to antibiotics (antibiotics are chemicals that kill bacteria)

Some Prokaryotes have a cell wall

Gives shape, support and protection to the plasma membrane and cytoplasm of the cell.

Eubacteria wall made of peptidoglycan* (protein-sugar molecules).

(* plant cell walls are made of cellulose)

Flagellum (flagella)

Some bacteria have one or more

Used for motility.

Pili

Short fibers projecting from the cell wall found on some bacteria.

They may help the bacteria cling to surfaces.

Capsule (or slime layer)

A special mucus-like protective coating found on some disease-producing bacteria.

Prokaryotic cells do not have membrane bound organelles

Reproduction in Prokaryotes

Binary Fission

Reproduction in Prokaryotes

Prokaryotes reproduce by binary fission “division in half”

Type of asexual reproduction

The cell replicates its genetic material

The cytoplasm divides by cytokinesis

Two identical daughter cells are produced (unless mutation occurs)

Review

Something interesting to finish...