Cellular Structure

Chapter 4

Eubacteria

Archaea

Eukarya

Eubacteria

Archaea

Eukarya

AnimaliaFungiPlantaeProtista

Monera (defunct)

Bacterial Structure

Outwardly, there is little to go by in bacterial structure

Bacteria may be of various shapes (morphologies)

Coccus = Spherical

Bacillus = Rod

Spiral = Spiral

Pleomorphic = Varied, Undefined

On a microscopic level there are layers of structure.

Glycocalyx = Outer Coating.

Flagella = Motive structures

Fimbriae and Pili = Attachment

Bacteria are divided into two large groups based on overall cellular structure

Gram Positive vs. Gram Negative

Gram Identity is about cell structure more than staining

Gram Positive = Single Membrane

Gram Negative = Double Membrane

EXCEPTION Mycobacterium

EXCEPTION Mycoplasma

Even exceptions to normal Gram staining can be classified by their overall structure and genetics.

Internal structure in bacteria is limited, but organized.

http://upload.wikimedia.org/wikipedia/commons/5/5a/Average_prokaryote_cell-_en.svg

Specialized internal structures are found in some bacteria.

EndosporesG+ structure to go dormant.

MagnetosomesMagnetite crystals for alignment

Storage Granules PHB Energy Storage

Eukarya Structure

Eukarya externally lack the complexity of Bacteria but are more internally structured

http://upload.wikimedia.org/wikipedia/commons/1/1a/Biological_cell.svg

There are three classes of organelles.

Non-membrane BoundRibosomes, flagella, etc.

Endomembrane SystemNuclear Membrane, ER, etc.

Non-Endomembrane Membrane-BoundMitochondria and Plastids

Non-Membrane Organelles

A Note on Evolution

Ribosomes

Public Domain - PDB

Cytoskeleton

Endomembrane System

Nucleus

Cell Nuclei inHeLa Cells

Public Domain Image-Wikipedia

The Nucleus has numerous functions

Contains the DNA of the Cell

Controls access to the DNA

Regulates division of the DNA

Endomembrane System

Wikimedia Commons

Mitochondria and Plastids

Mitochondria

Chloroplasts

These organelles share a number of unique characteristics

Internal DNA Each possess a small circular piece of DNA

RibosomesEach possess ribosomes internal to their structure

Binary FissionBoth reproduce independent of the cell cycle.

Endosymbiotic Theory

Aerobic Eubacteria

Photosynthetic Eubacteria

Protoeukaryote

Aerobic Eukaryote

Photosynthetic Eukaryote

Various lines of evidence support this theory.

Organelle ribosomes more closely resemble bacterial ribosomes than eukaryotic ribosomes.

DNA of Mitochondria is closely related to Rickettsia bacteria.

DNA of Chloroplasts is closely related to blue-green photosynthetic bacteria.