BIOL 255 Ch. 3 - Prokaryotic Cell

What components of eukaryotic cells are explained via Endosymbiotic theory

Chloroplasts & mitochondria

What evidence supports Endosymbiotic theory

• DNA in chloroplasts and mitochondria is different from cell DNA & is similar to bacterial DNA

• Contains separate ribosomes from rest of cell (resembles bacterial ribosomal structures

• double membrane around chloroplasts and mitochondria

• shape and size of chloroplasts and mitochondria is similar to bacteria

• replicate separately without instruction from nulcleus

• divide via binary fission (same division as bacteria uses

Describe common cell morphologies and cellular arrangements typical of prokaryotic cells and explain how cells maintain their morphology

• Morphologies: coccus (spherical), bacillus (rod), vibrio (comma), spirochete (helical & flexible), spirillum (helical & rigid), coccobacillus (short & plump)

  • Pleomorphism: no defined shape, has variation in shape and size within species

• Arrangements: based on planes of division

  • Diplo (pairs), strepto (chains), staph (irregular clusters), tetrad (groups of 4), sarcinae (cubes of 8)

• How morphology is maintained

Explain the difference between cell morphology and arrangement. What are the two factors that cellular arrangement depends on?

Morphology: shape of the cell

Arrangement: how the cells are clumped together

• Planes of division

• whether or not the cells stick together after division

Which spiral-like bacterial cell shape uses the interior periplasmic flagella?

Spirochete

What is the importance of a large surface to volume ratio in bacteria?

Increases the number of openings into cell membrane for nutrients to be brought into the cell

Higher the ratio, the faster the cell can replicate

What is the difference between motility and attachment?

Motility: ability of cell to move

Attachment: ability of cells to attach to other cells and exchange DNA info

Describe the function of the fimbriae, pili, flagella, and axial filaments and be able to distinguish between them. Also include whether they are involved in attachment, motility, or both

Fimbrae: many small filaments involved in attachment (bacterial velcro)

Pili: Tubular structures for exchange of DNA & attachment

Flagella: long tail like structure that provides motility

Axial filaments: Internal structure that gives motility through springing motion (spirochetes)

What are the four possible arrangements for prokaryotic flagella?

Monotrichous: singular flagella

Lophotrichous: multiple flagella emerging from single location

Amphitrichous: flagella at both ends of cell

petritrichous: flagella dispersed all over cell surface

Describe what causes a bacterial cell to move via chemotaxis. Explain how the prokaryotic flagellum orchestrates the movement (i.e., what two things can the flagellar movement cause the cell to do?) Name two examples of a stimulus for chemotaxis

Chemotaxis: cell is attracted to or repelled from a stimuli based on concentration gradient

Run: Counterclockwise movement

Tumble Clockwise movement

phototaxis: light stimulus

chemotaxis: chemical stimulus

Describe the difference between the movement of exterior flagella and the interior periplasmic flagella

Exterior - rotation / spin

Interior - springing

What are the two forms of a glycocalyx?

Slime - loosely attached & loosely organized

capsule - tightly attached & highly organized

What benefits does a glycocalyx give to a bacterial cell?

dehydration, nutrient loss, pathogenicity (evade phagocytosis), formation of biofilms

What is peptidoglycan made of?

Peptid = protein

glycan = sugar

What advantages do cell walls provide for bacterial cells?

determines cell shape

prevents lysis due to change in osmotic pressure

Compare and contrast the Gram-positive and Gram-negative cell wall structure

Gram Positive:

• Thick peptidoglycan layer

• periplasmic space

• cell membrane

Gram Negative:

• outer cell membrane

• thin peptidoglycan layer

• periplasmic space

• cell membrane

Describe the outer membrane and its importance.

Contains Lipopolysaccharides

• Lipid A - Endotoxin

  • causes overreaction in immune response

• Polysaccharides - antigen

• Porins - protein channels through membrane

Why does Crystal Violet fail to crystalize in the peptidoglycan of gram-negative bacteria?

Gram iodine causes dye to crytallize

the outer membrane becomes bonded to the dye

outer membrane is removed during addition of ethanol

What color would you expect gram-positive and gram-negative bacteria to stain after a Gram-stain?

Gram-positive = purple

Gram-negative = pink/red

What is it called when a bacterial cell has no defined shape

pleomorphic

EX: mycoplasma

What is special about the cell wall structure of Mycobacterium?

contains lipid mycolic acid

• pathogenticity

• high resistance to certain chemicals and dyes

Name 3 functions of the prokaryotic cell membrane

1. Selectively permeable barrier

2. location of ATP formation

3. Interacts with external environment

Describe the differences between bacterial and archaeal plasma membranes

Bacteria = Ester

Archaea = ether, can have phospholipid monolayer

Describe the characteristics of the nucleoid

• no nucleus/nuclear envelope

• chromosome

  • singular

  • circular

  • double stranded DNAA

  • contains all DNA required by cell

What is the difference between a bacterial chromosome and a plasmid?

Bacterial Chromosome = essential DNA for function of Cell

plasmid = nonessential extra DNA

What is the importance of plasmids?

provides very beneficial traits to the cell: antibiotic resistance

replicates independently of the chromosome

What is the ribosome responsible for?

Protein synthesis

What kind of ribosomes do prokaryotes have?

70S

made of large subunit (50S) & small subunit (30S)

What is an inclusion and what are their functions?

Intracellular storage of nutrients, metabolic end products, energy, building blocks

can be used when environmental sources are used up

What is a micro compartment used for?

non-membrane bound storage location with specific function

EX:RuBisCO for CO₂ Fixation

What is the purpose of a bacterial cell forming an endospore?

specialized cell type that are metabolically dormant

capable of high resistance to extreme conditions & long-term survival

What is sporulation?

formation of endospores as a means of protection

What is germination?

Return to vegetative growth

What makes endospores different than fungal spores?

Fungus: Germination = spores created, dormant = not reproducing

Bacteria: Germination = growth, dormant = active

What location of the cell can spores develop?

Central: middle

Terminal: At end

Subterminal: close to one end

Swollen Sporangium: spore is larger than cell

What property of endospores makes them more resistant to desiccation, heat and radiation?

They are already dehydrated

What are two genera of bacteria that are obligate intracellular parasites?

Rickettsias

Chlamydias

What are the unique features of Archaea?

Contain unique genetic sequences in rRNA

Have unique membrane lipids and cell walls

Extremophiles: adapted to heat, salt, acid pH, pressure, and atmosphere