two main classes of cells - home - faculty · size ave. size 1-10 µm ave. size 10-100 µm nucleus...

1

Prokaryotic and Eukaryotic Prokaryotic and Eukaryotic CellsCells

Two Main Classes of Cells

• Prokaryotic (Bacteria and Archaea)– Pro = “Before”; Karyon = “Kernel”– No nucleus, DNA coiled up inside cell

• Eukaryotic (Everything else)– Eu = “True”– DNA inside membrane bound organelle inside

cell, the nucleus

3 Domains of LifeEukaryotic Cell (non bacterial)

Prokaryotic Cell (bacteria)

Size DifferencesCell Size: Prokaryotes and eukaryotic cell

2

Prokaryotic Diversity: K. Monera• 4000 described species

– Estimated range 400,000-4 million sp.

• Minimal structural diversity

• Tremendous metabolic diversity

• Ecological roles and pathogenesis

Prokaryotic Cell

Bacterial Size, Shape and ArrangementCoccus Bacillus Spiral

Prokaryotic Cell

The Capsule: Frederick Griffith, 1928

• Enhances virulence: attachment and resistance• Forms the foundation of “biofilms”

Gram staining: A clinical tool for distinguishing cell wall composition (Gram-positive and gram-negative bacteria)

3

Common bacterial CELL WALL structures as revealed by Gram staining:

Gram positive: thick peptidoglycancell wall

Gram negative: thin peptido. wall + outer memb.

Bacterial Motility: Flagella

Bacterial Growth: Binary fission a simple division process

Movie 1

Movie 2

Ecological Importance Bacteria and Cyanobacteria

• Nutrient Cycling:– Decomposers– Carbon fixation– Nitrogen fixation– Others

• Symbioses:– Mutualistic: +/+– Commensalistic: +/o– Parasitic: +/-

• Foreign pathogens• Opportunistic pathogens

Prokaryotes• Low morphological diversity (how they looks)• HUGE metabolic diversity!

All organisms can be divided into either of two major groups based upon their pattern of cell structure:

Characteristic Prokaryotic Cell Eukaryotic Cellsize ave. size 1-10 µm ave. size 10-100 µm

nucleus nucleoid(no membrane)

membrane bound

chromosomes single circ. loop ofnaked DNA

linear, arranged withhistones in pairs

organelles absent present, vary withcell function

ribosomes present as smaller 70Sform

present as larger 80Sform

flagella Solid core made offlagellin

9+2 arrangement ofmicrotubules

cell wall present in most sp. aspeptidoglycan

absent or different incomposition

cell reproduction binary fission mitosis and sexualreproduction

4

Animal Cell Plant Cell

Evolution of Eukaryotic Cells

• Limits of the P.M.– Surface area revisited

• Differentiation of P.M.• Formation of Organelles

– Compartmentalized Reaction centers– Increase Membrane Surface area– More efficient Metabolism– Increase DNA…which means?

• Leads to Eukaryotic cells…

Eukaryotic Cell Structure: The Factory• Plant and Animal Cell Structure

– Nucleus: the control center– Cytoplasm and Ribosomes: site of protein synthesis– Endoplasmic Reticulum: plumbing, lipid and protein

synthesis– Golgi Apparatus and the secretory pathway– Lysosomes: digestive activity– Chloroplasts and Mitochondria: food and ATP energy– Vacuoles: storage/digestion– Cytoskeleton: structure and movement– Plant Cell Wall: structure, osmosis and turgor pressure

• Family Photos-- structural and functional specializations

Animal Cell The Nucleus•Chromatin= DNA + proteins

•Nucleolus= site of ribosome production

•Endomembrane system

•Interrelated membrane “network” inside of cell

5

The Nucleus and Protein Synthesis

Ribosomes

• Protein Synthesis• Free- endogenous proteins• Bound- secretory and membrane bound proteins

The “real” Ribosomes

The Endoplasmic Reticulum• Huge Surface Area• General functions• Rough endoplasmic

reticulum (RER)– Makes more membranes, – Modifies proteins

• Smooth endoplasmic reticulum (SER)– Makes lipids, steroids,

hormones, etc– Detox in the liver– Storage

How the Rough ER Works

6

The Golgi ApparatusStorage, refinement, and shipping of ER products

Works in partnership with ER

ER and Golgi complex

Lysosomes

•Sacks of digestive enzymes which break down molecules and organelles in the cells

•Digest food, fight invaders, clean house

•pH of 5

•Apoptosis

•Disorders

Figure 4.10 Lysosome formation

Vacuoles• Sacks which can store enzymes, proteins,

water, and cellular byproducts, waste.• Plants cells often have large Central

Vacuole which holds water and other stuff• Vacuoles also transport things from one

organelle to another withinthe cell

Plant Cell

7

Vacuoles Mitochondria and Chloroplasts

• Role in Energy Transformation– Photosynthesis– Cellular respiration

• Evolution– Endosymbiosis Theory

The Chloroplast•Most of the living world depends on chloroplasts for its energy!

•Two membranes on outside

•Complex membrane structure on inside

The Mighty MitochondriaSites of cellular respiration and ATP synthesis

The CytoskeletonThe “skeleton, muscles and highway” of a cell

Cilia and Flagella

8

A comparison of the beating of flagella and cilia Support and Joining of Cells

Support and Joining of Cells