Post on 23-Dec-2015
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2.2 Prokaryotic Cells
“primitive cells”
cells that lack membrane-bound organelles
ie: no nucleus, no mitochondria, no vacuoles, etc
Ex: bacteria (ie E. Coli) – found in soil, water, on your skin, in your intestine
Ex: blue green algae
Prokaryotic Cells
organisms that are made of prokaryotic cells.
Most prokaryotes are unicellular, such as bacteria, however, they can be multicellular too, such as blue green algae
Prokaryotes
E. coli
Blue- Green Algae
Prokaryote Cell Structue
CELL SURFACE MEMBRANE / PLASMA MEMBRANE: Thin layer composed of phospholipids Controls the entry/ exit of substance via active
or passive transport Selectively permeable
Prokaryote Cell Parts
CELL WALL: Rigid to semi-rigid wall surrounding the plasma
membrane. Contains pores to allow passage of materials in
and out of the cell. The Cell wall supports the cell and provides
shape
Prokaryote Cell Parts
SLIME CAPSULE: Protective outside layer, found outside the cell
wall Also known as “surface layer” or the “S-layer” Protects the cell from environmental dangers Contains proteins and or glycoproteins
Prokaryote Cell Parts
Cytoplasm: The “inside” of the cell Contains cytosol (fluid of the cell) Contains the enzymes (biological catalysts) for
catalyzing chemical reactions of metabolism Contains ribosomes and naked DNA No membrane bound organelles!
Prokaryote Cell Parts
NUCLEOID: Region of the prokaryotic cytoplasm where
genetic information is found (1 main chromosome and plasmids)
The 1 chromosome is made of NAKED DNA This means that the DNA is not bound to proteins
(like histones) This reduces the amount of space they take up Usually circular
Prokaryote Cell Parts
PLASMID: Small, circular, naked, DNA Smaller, and contains less information than the
chromosome. Found in the nucleoid region
Prokaryote Cell Parts
Mesosome: Indentation in the cell membrane of bacteria Unknown function, produced by chemical
fixation techniques.
Prokaryote Cell Parts
RIBSOSOME: Made of RNA and proteins Makes proteins Less dense than eukaryotic ribosomes
Prokaryote Cell Parts
FLAGELLUM: threadlike, motile proteins structures and are
used for locomotion Cell may have none, 1, or several
Prokaryote Cell Parts
PILI (plr) / PILUS (singlular): Thin protein tubes found outside the plasma
membrane and extend out from the slime capsule
Attachment Pili Have sticky ends that allow it to attach to
surfaces (i.e. another cell) Conjugation Pili (Sex Pili)
Longer Build a bridge between 2 bacterial cells allowing
for exchange of DNA (conjugation)
Prokaryote Cell Parts
Prokaryotic cells divide asexually by binary fission (similar to mitosis)
They duplicate their chromosome (their circular DNA) and then split in half (each new daughter cell gets half the cytoplasm and 1 chromosome)
Prokaryotic Reproduction
Since binary fission is a form of asexual reproduction, the daughter cells produced are identical to the original parent cell.
Conjugation (with the help of conjugation pili) allows for genetic variation – allows for a new combination of DNA
Annotate and Identify Structures from and electron micrograph of E. Coli
ribosome
Nucleoid region (DNA, plasmid)Cell wall
cytoplasmPlasma membrane
No visible slime capsule in this diagram
PILUS
SLIME LAYER
Metabolic Activity of Prokaryotic Cells
1. Photosynthesis: light + CO2 + H2O C6H12O6 + O2
2. Nitrogen Fixation: Convert nitrogen from an unusable from to a usable form
3. Fermentation: convert organic substances into simpler substances (ie sugar into ethanol)