Ch. 4: Functional Anatomy of Prokaryotic And Eukaryotic Cells

Cell Theory

All living cells can be divided into two groups: prokaryotic and eukaryotic

• Plants and animals are entirely composed of eukaryotic cells. Also fungi, yeasts, molds, protozoa, and algae

• Bacteria and archaea are prokaryotes

Name all differences in the nuclear bodies of Pro- and Eu-

Pro-:

• Nuclear body not enclosed within a nuclear membrane 

• One circular chromosome associated with non-histone proteins (Bacteria)

• No Nucleolus 

• Lacks membrane-bound organelles 

Eu-:

• Nuclear body is enclosed within a nuclear membrane and seperated from cytoplasm 

• Multiple chromosomes associated with histone and other proteins 

• Distinct nucleolus 

Name all differences in the Cell division

Pro-:

• Binary Fission (No mitosis)

  • Everything is an exact copy

• Meiosis not needed

Eu-:

• Mitosis

• Sex cells are mproduced during meiosis

Name all differences in the cell wall

Pro-: 

• Most have one

• Almost always contains the complex polysaccaride peptidoglycan 

Eu-:

• When present: is chemically simple.

• Never composed of peptidoglycan 

Name all differences in the motility

Pro-:

• Most have flagella of simple construction

• No Cilia

Eu-: 

• May have flagella or cilia of complex construction 

• Flagella and cilia are organelles involved in movement of the cells

Differences in ribosome

Pro-:

• Smaller 70s ribosomes 

Eu-:

• Larger 80s, except for some 70s in some organelles 

Function of Plasma membrane

Selectively permeable membrane enclosing the cytoplasm of a cell; the outer layer in animal cells, internal to the cell wall in other organisms

Function of Ribosomes

Site of protein synthesis in a cell. Compsoed of RNA and protein 

Endosymbiotic Theory

• Something living inside something else 

• Theory that smaller prokaryotes live inside larger eukaryotes and become organelles

  • Mitochondria and chloroplasts have 70S ribosomes similar to those of prokaryotes 

Virus Classification

Viruses are neither pro- or eukaryotes.

• Non-living organisms but considered microorganisms die to infectious nature

• Not composed of cells and uses machinery within living host cells to multiply 

• Simiplier than simple cells

Bacteria Prokaryotic Cell

• Bacteria is prokaryotic

• Single cell

• Most have cell wall

• Bacterial Colony is clusters of millions of bacteria growing on a solid surface (All are identical due to binary fission)

Size, Shape and Arrangement of Bacteria: What are the common shapes?

They can come in one of three basic shapes

• Coccus (Spherical), Bacillus (Rod), and Spiral

Spherical Coccus:

• Pairs: Diplococci 

• 4s: Tetrads

• 8’s: Sarcina

• Chains: StreptoCocci

• Grape-like Clusters: Staphlococci

Rods: Bacilli

• Pairs: Diplobacilli 

• Chains: Streptobacilli 

• Ovals, no straight edge: Coccobacilli 

Spiral:

• Spirillum 

• Curved Rod shape: Vibrios

• Many Tight coils: Spriochetes

Monomorphic vs. pleomorphic

Monomorphic: One shape

Pleomorphic: Cell has many shapes, not just one 

• Doesn’t change shapes, but has many shapes simultaneously 

Glycocalyx

External to Cell Wall

• Substances that surround the cell (Sugar Coats)

• Composed of either polysaccarides, polypeptides, or both

• Capsule: Glycocalyx is organized. Function is to attach to host and cause disease

• Slime Layer: Unorganized and loosely attached to cell wall

• Shown with negative staining

Bacterial Capsule

External to Cell Wall

• Resists phagocytosis (WBC)

• Adheres to environmental surfaces

• Colonize and resist flushing from host

• Increases virulence on pathogenetic species 

• Protects cell from dehydration and loss of nutrients 

Biofilm

External to Cell Wall

• Microbial community that forms a slimy layer on surface.

• Acts like double side tape

• Capsule is important component for biofilm

• Can be both beneficial to protect mucosal membrane from harmful microbes, but can harmful (dental plaque)

Flagella

Provides Motility

• Atrichous: Bacteria that lack flagella and is non-motile 

• Needs electron microscope to view 

• Basal Body anchors flagella to cell wall and plasma membrane

Arrangements of Flagella 

• Monotrichous: Single Polar flagella

• Amphitrichos: Single Flagella at both ends

• Lophotrichous: More than one flagella at each end 

• Peritrichous: All over cell

Flagella Action: Movement of flagella toward or away certain stimulus is called taxis

Flagellar Protein: 

• H-antigen: used for distinguishing among variations withina species of Gram - Bacteria 

Axial Filaments 

Spirochetes: Move by means of axial filaments

• Similar to flagella, but located under outer membrane of Gram -Negative cell wall and spiral around cell cell

• Drilling motion (How a corkscrew moves through a cork)

Fimbriae and Pili

• found in almost all Gram - bacteria and not many Gram + bacteria

• Fimbriae used for attachment.

  • Involved in biofilm formation

• Important for virulence to attach to host cell

Pili:

• For the transfer of DNA from one cell to antooher. Also involved in motility

Cell Wall

Forms the shape of the cell

• Protection of the cell and anchorage for flagella

• ALMOST all prokaryotes have a cell wall

  • Differs chemically from cell wall of eukaryotes, which are simple

Gram-positve Cell wall characteristics

Many layers of peptidoglycan

• Gluycan Portion:

  • alternating NAG and NAM molecules, linked in rows from 10-65 sugars to form carb backbone

• Peptide Portion

  • Adjacent rows of carbohydrate backbone are linked by polypeptide 

  • Tetrapeptide side chains consist of 4 amino acids attached to NAM in the backbone 

• HAS TEICHOIC ACIDS 

Gram-Negative Cell Wall characteristics 

• one or very few layers of peptidoglycan and outer membrane of protein and fat 

• Periplasm: Fluid between outer membrane and plasma membrane

• NO TEICHOIC ACID

• more suseptible to mechanical breakage due to small amount of peptidoglycan

Outer membrane consists of lipopolysaccharides, lipoproteins and phospholipids 

• Evades phagocytosis 

• Serves as barrier

• Resistant to digestive enzymes, lysosomes, and certain detergents 

Porins also located in outer membrane

• LPS: contains Lipid A(endotoxin) and o-polysaccarides (functions as antigens and are useful for distinguishing species)

Importance of difference between Gram-Negative and Gram-Positive

• Ability to identify bacterium 

• Choose best control method

  • eg. penicillin prevents construction of peptidoglycan layer of cell wall, killing cell

• Outer membrane in Gram - plays a protective role

Gram Staining

Primary Stain: Crystal Violet(All bacteria stain violet)

• Mordant (Fixes stain into cells): Iodine (cell becomes darker violet)

• Dehydrating Agent: Alcohol (45% ethanol) or acetone/alcohol blend (only for Gram -)

• Counterstain: Safranin (Gives light pink color)

Gram- is pink while Gram + is purple

Plama Membrane

Inside cell wall and encloses cytoplasm

• Made of phospholipids and proteins

• Lipid bilayer

• Serves as a selective barrier (materials exit and enter cell)

• selective permeability

• Contains enzymes for production of energy

• Several antimicrobial agents can specifically damage plasma membrane

• Group of antibiotics can disrupt membrane phospholipid bilayer, causing ICF to leak, leading to cell death

Cytoplasm

Prokaryotic Cells: Substance inside plasma membrane 

• Semi-liquid contents of cell

• Complex mixture of chemicals 

• site of most bacterial metabolism 

Ribosomes 

• Internal to cell wall

Protein synthesis 

Protein and rRNA 

• Bacterial ribosomes are 70s ribosomes(Humans have ths in mitochondria) while eukaryotic ribosomes are 80S (30S+50S Subunits)

• Several antibiotics work by inhibiting protein synthesis here

Inclusion Bodies

• Internal to Cell Wall

Stores nutrients (use in times of starvation)

Magnetosomes: Iron oxide acts like magnets 

Volutin: inorganic phosphate 

Nuclear Area

• Nucleoid Single long, continuous, and circular double stranded DNA (genetic Material)

• No nuclear membrane or histone protein 

• 20% of cell volume is occupied by DNA in a growing bacterium 

• Need electron mcroscope to view 

• Bactira often contains small, circular, double stranded DNA called plasmids

  • Small loops of entrachromosolmal DNA 

  • Not required for cell survival udner normal conditions 

  • genes for virulence or drug resistance 

  • Plasmids can be transferred from one bacterium to another via pili

  • USed for gene manipulation in biotechnology

Endospore

Survival Formal of bactier

• Locally terminal(at one end), subterminally (near one end) or centrally inside vegetative cell(active cell)

Sporulation: Process fo endospore formation within vegitative cell

Germination: Endospore returns to its vegetativstate via a process which does not increase number of cells

• They can survive boiling, freezing, drying, and vacuum, radiation, many disinfectants, and can stay dormant for very long periods of time.