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 Structure

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 cytoplasm Plasma membrane No visible slime capsule in this diagram

PILUS SLIME LAYER

Metabolic Activity of Prokaryotic Cells 1.Photosynthesis: light + CO 2 + H 2 O  C 6 H 12 O 6 + O 2 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)