functional anatomy of prokaryotic cells

key functions of cells:

• A boundary(made of of cell membranes and cell walls) that keeps the cellular contents separate from the external environment but allows for the transfer of some substances into and out of the cell

• Replication of DNA

• Synthesis of cellular component

• The ability to obtain energy through metabolic processes

What description best fits prokaryotic cell(bacterium)

• Smaller (1-10 u M)

• Simpler in structure

• DNA concentrated in nucleiod region, which is not separated from the rest of cell by a membrane

• DNA found as a single, circular chromosome

• Lacks most organelles 

• Rigid cell wall found outside outer wrapper(cell membrane)

• Cell always present

What description best fits eukaryotoic cells

• Larger (10-100 u m)

• More complex structure

• Nucleus enclosed by membrane

• Contains many types of organells

• DNA found in several linear chromosomes

• Wont have cell wall if animal cell, but plant and fungal cells do

  • Rigid cell wall found only surrounding plant and fungal cells

Prokaryote:

One circular chromosome, not in a membrane

•No histones(A protein associated with DNA in eukaryotic chromosomes)

•No organelles

•Bacteria: peptidoglycan cell walls

•Archaea: pseudomurein cell walls

•Divides by binary fission

Eukaryote:

•Paired chromosomes, in nuclear membrane

•Histones

•Organelles

•Polysaccharide cell walls, when present
•Divides by mitosis

The size, shape, and arrangement of bacterial cells

• Average size: 0.2 to 2.0 um diameter x 2 to 8 um length

• Most bacteria are monomorphic(single shape)

• A few are pleomorphic (many shapes)

• three basic bacterial shapes

  • coccus (spherical)

  • bacillus (rod-shaped)

  • spiral (twisted).

What is single shaped bacteria called?

monomorphic

What kind of bacteria can assume several shapes?

pleomorphic

Spiral bacteria:

• Spiral

  • Vibrio, curved rods/always comma or c shaped, dont have flagella, has a lot of pathogenic species

  
  

  • Spirilium, helical shape, like a corkscrew, ridgid bodies
    

  • Spirochete, flagella goes all around the cell, move by axial filaments, pathogenic ,

    • best known is Treponema padillum

    • boreliella burgdorferi

Cocci:

• Clusters: staphylococci

• Chains: steptococci

• Groups of four: tetrads

• Cubelike groups of eight: sarcinae

What is a cluster of cocci

staphylococci

What is a chain of cocci?

streptococci

What is cocci in Groups of four:

tetrads

What are cocci in Cubelike groups of eight:

sarcinae

Bacilli:

• Pairs: diplococci, diplobacilli

• Chains: steptobacilli

• Groups of four: tetrads

• Cubelikle groups of eight: sarcinae

What is a pair of bacilli called?

diplococci, diplobacilli

What are chains of bacilli called?

streptobacilli

What are groups of four bacilli called?

tetrads

What are cubelike groups of eight of bacilli called?

sarcinae

Prokaryotic cell structure:

• Glycocalyx(sugar coat): term to describe substanaces that surround bacterial cells

• External to the cell wall

• Viscous and gelatinous

• Made of polysaccharide and/or polypeptide

• All bacterial cells have glycocalyx 
  
  

• Capsule

  • If subsbtance is organized and firmly attached to cell wall

  • A lot of pathogens have capsules, makes them stronger in causing disease 

• Slime layer

  • If substance is unoragnized and loosely attached to cell wall

What is the Glycocalyx(sugar coat)?

term to describe substanacces that surround bacterial cells

What part of prokaryotic cell structure is being described here?

• If subsbtance is organized and firmly attached to cell wall

• A lot of pathogens have capsules, makes them stronger in causing disease 

capsule

What part of prokaryotic cell structure is being described here?

• If substance is unoragnized and loosely attached to cell wall

slime layer

What are the functions of capsules :

• Prevents drying out or dessication

• Allows bacteria to adhere to various surfaces

  • Steptococcus mutans - enamel on teeth to cause dental carries 

  • Klebseilla pneumoniae- attaches to respiratory tract

  • Steptococcuus pneumoniae- causes pneumonia

• Contribute to virulence(degree of pathogenicity) of bacteria by prevent phagocytosis by WBC’s

Appendages are basically involved in movement or adhesion

Flagella (singular flagellum) are cellular appendages that consist of three parts:

• Made of protein flagellin

• A filament that rotates for movement

• A hook where the filament attaches

• A basal body that anchors the hook to the cell 

• The arrangement of the hook/basal body articulation allows the hook with its filament to rotate 360

What does the filament of a flagella do?

rotates for movement

What is the hook of a flagella

where the filament attaches

What is the basal body of a flagella

anchors the hook to the cell 

The arrangement of the hook/basal body articulation allows the hook with its filament to….

rotate 360

Flagellar arrangement

• Atrichous: no flagella

• Peritchous: many around

• Monotrichous: one only

• lophotrichious : multiple at one end

• Amphitrichous: at both ends 

What does no flagella mean?

Atrichous

Flagellar arrangement:

What does Peritchous mean

many around

Flagellar arrangement:

What does Monotrichous mean

one only

Flagellar arrangement:

What does lophotrichious mean

multiple at one end

Flagellar arrangement:

What does Amphitrichous mean

at both ends

What are

• modified flagella that occur in spirochetes

• found only in spirochetes (flexible spirals

axial filaments

Examples of axial filaments

• Treponema padillum 

  • causes syphillis

• Borrelia burgdoferi

  • Causes lyme disease

Flagella

• Flagella allow bacteria to move toward or away from stimuli (taxis)

• Flagella rotate to “run” or “tumble”

• Flagella proteins are H antigens and distinguish among serovars(e.g. Escherichia coli O157:H7)

What allows bacteria to move toward or away from stimuli (taxis)

flagella

Flagella rotate to….

“run” or “tumble”

Flagella serve chemotaxis:

• Chemotaxis

  • Directed movement 

  • In response to a chemical

  • Through a specific chemorecptor on the cell

• Movement to a chemical: chemical is a chemoattractant (e.g. sugar, amino acid)

• Movement away from chemical: chemical is a chemorepellent(toxic substance)

What is being described here?

• Directed movement 

• In response to a chemical

• Through a specific chemorecptor on the cell

chemotaxis

Movement to a chemical: chemical is a

chemoattractant (e.g. sugar, amino acid)

Movement away from chemical:

chemical is a chemorepellent(toxic substance)

Archaella:

• Archaeal motility structure 

• Made of glyocoproteins archaellins

• Anchored to the cell

• Archaella (singular: archlaellum) rotate like flagella 

Fimbriae and Pili:

• Fimbriae:

  • Hairlike appendages that allow for attachment

• Pili:

  • Involved in motility(gliding and twitching motility)

  • Conjugation pili involved in DNA transfer from one cell to another 

What is the Hairlike appendages that allow for attachment

fimbriae

What is …

• Involved in motility(gliding and twitching motility)

• Conjugation pili involved in DNA transfer from one cell to another 

Pili

Fimbria and Pili:

• Cell appendages in mostly gram-negative bacteria

• Made out of protein subunits (pilin)

• Thinner than flagella 

• Fimbria

  • A few - hundreds

  • Main function is attachment

  • Neserria gonorrhoeae

  • E. coli (pathogenic)

• Pili

  • Typically 1 or 2 only and longer

  • DNA transfer: specialized sex pili transfer conjugation

  • Twitching motility and gliding motility

Fimbria

• A few - hundreds

• Main function is attachment

• Neserria honorrhoeae(std)

• E. coli (pathogenic)

Pili:

• Typically 1 or 2 only and longer

• DNA transfer: specialized sex pili transfer conjugation

• Twitching motility and gliding motility

Compostion and characteristics of cell wall:

• Peptidoglycan

  • Polymer of a repeating disaccharide in rows:

    • N-acetyglucosamine (NAG)

    • N-acetylmuramic acid (NAM)

    • NAM and NAG molecules are linked in rows of 10 to 65 sugars to form a carbohydrate “backbone” (the glycan portion of peptidoglycan)

• Rows are linked by polypeptides

  • Adjacent rows are linked by polypeptides (the peptide portion of peptidoglycan). Although the structure of the polypeptide link varies, it always includes tetrapeptide side chains, which consist of four amino acids attached to NAMs in the backbone.

hiearchy of classifcation of organisms

• Domain

  • bacteria

  • archae

  • eukaryote

• kingdom

• phylum

• class

• order

• family

• genus

• species

• mnemonic to remember the hierachry:

  • dead kings played chess on fat girls stomach

Gram positive cell walls

• Teichoic acids (only present in gram-positive)

  • Lipoteichoic acid cell wall to plasma membrane

  • Wall teichoic acid links the peptidoglycan

    • Holds all stacks together

  • Carry a negative charge 

  • Regulate movement of cations

• Polysaccharides and teichioic acids provide antigenic specificity

• cell wall has many layers of pepdtidoglycan, forming a thick ridgid structure

• highly susceptibilty to penicillin

• disrupted by lyzosome

• produce exotoxins(make toxin and put it outside cell)

Gram-negative cell walls

• Periplasm between the outer membrane and the plasma membrane contains peptidoglycan

• Outer membrane made of polysaccharides,  lipoproteins, and phospholipids

• Protect from phagocytes, complement, and antibiotics

• Made of lipolysachharide (LPS)

  • O polysaccharide functions as antigen (e.g., E. coli O157:H7(how it became pathogenic))

  • Lipid A is an endotoxin embedded in the top layer

• Porins(proteins) form channels through membrane 

• Has very thin layer of peptidoglycan, they are more susceptible to mechanical breakage

Which of the following only contain Teichoic acids

gram-positive cell walls

Outer membrane of gram-negative cell consists of:

Lipopolysaccharide:

• Lipid A

  • The culprit for fever (endotoxin)

    • as long as its embedded in top layer of outer membrane, its harmless, but when bacteria dies the cell wall disinigrates, lipid A (which functions as an endotoxin) enters blood stream causing fever

  • Highly conserved

• Core sugar

  • Conserved

  • structural- provides stability

• Sugar chain of varying length (O-antigen, “ohne Hauch, used for typing)

  • functions as an antigen

gram-positve stain color:

purple

gram-negative stain color:

red

Cell walls and the gram stain mechanism:

• Crystal violet-iodine crystals form inside cell
• Gram-positive
– Alcohol dehydrates peptidoglycan
– CV-I crystals do not leave
• Gram-negative
– Alcohol dissolves outer membrane and leaves holes in peptidoglycan
– CV-I washes out; cells are colorless
– Safranin added to stain cells

Prokaryotic and eukaryotic cells are similar in their

chemical composition and chemical reactions

What cells lack membrane-enclosed organelles (including a nucleus)

prokaryotic cells

Peptidoglycan is found in

prokaryotic cell walls but not in eukaryotic cell walls

What kind of cells have membrane-bound nucleus and other organelles

eukaryotic cells

The prokaryotic cell, bacteria

1. Bacteria are unicellular, and most of them multiply by binary fission.

2. Bacterial species are differentiated by morphology, chemical composition, nutritional requirements, biochemical activities, and source of energy

Bacteria have unique cell structures that can be targets for…

antibiotics, immunity, and phage infection

What is a gelatinous polysaccharide and/or polypeptide covering

glycocalyx (capsule, slime layer, or extracellular polysaccharide)

What may protect pathogens from phagocytosis

capsules

What enables adherence to surfaces, prevent desiccation, and may provide nutrients.

capsules

Bacterial flagella and archael archaella, do what to push the cell

rotate

What are relatively long filamentous appendages consisting of a filament, hook, and basal body

flagella

Motile bacteria exhibit taxis

positive taxis is movement toward an attractant, and
negative taxis is movement away from a repellent.

What is positive taxis?

movement toward an attractant

What is negative taxis?

movement away from a repellent

Flagellar (H) protein is an

antigen

Spiral cells that move by means of an axial filament (endoflagellum) are called

spirochetes

Axial filaments are similar to flagella, except that they…

wrap around the cell

What help cells adhere to surfaces

fimbriae

What surrounds the plasma membrane and protects the cell from changes in water pressure

cell wall

The bacterial cell wall consists of…..

peptidoglycan, a polymer consisting of NAG and
NAM and short chains of amino acids.

What consist of many layers of peptidoglycan and also contain teichoic acids

Gram-positive cell walls

What kind of bacteria have a lipopolysaccharide-lipoprotein-phospholipid outer membrane surrounding a thin peptidoglycan layer.

gram-negative

What does the outer membrane of the cell wall do

protects the cell from phagocytosis and from penicillin, lysozyme, and other chemicals.

What are proteins that permit small molecules to pass through the outer membrane; specific channel proteins allow other molecules to move through the outer membrane

porins

What component of the outer membrane consists of sugars (O polysaccharides), which function as antigens, and lipid A, which is an endotoxin

lipopolysaccharide