Prokaryotic Cells Flashcards
What features define prokaryotes?
- semi-permeable barrier
- all contain ribosomes
- do not contain membrane-bound organelles or a nucleus
- genetic material organized into a single circular molecule of DNA concentrated in the nucleoid region
- single-celled organisms
- primitive cytoskeleton
- lack mitochondria so use cell membrane for ETC and generation of ATP
What are the 3 domains that classify life?
- archaea (prokaryote)
- bacteria (prokaryote)
- eukarya
Archaea
- single-celled organism
- live in really extreme environments
- similar overall structure to bacteria
- genes and metabolic pathways similar to eukaryotes
- use photosynthesis or chemosynthetic sources or inorganic compounds to generate energy
- contain a single chromosome
- divide by binary fission or budding
- resistant to many antibiotics
Why is it believed that eukaryotes and archaea share common origin?
both start translation with methionine, contain RNA polymerases, and associate their DNA with histones
Bacteria
- all contain cell membrane and cytoplasm – some have flagella or fimbriae
- share analogous structure to eukaryotes
What is the ratio at which bacteria outnumber human cells in the body?
10:1
Explain the relationship between the human body and mutualistic symbiotic bacteria
- both benefit from relationship
- Ex: bacteria in gut produce vitamin k and biotin which prevents overgrowth of harmful bacteria
Explain the relationship between the human body and pathogens/parasites
- provide no advantage to the host
- cause disease
- can live intra- or extra-cellularly
Bacteria Classification by Shape (3)
- cocci: spherical, “___coccus”
- bacilli: rod-shaped, “_____bacillus”
- spirilli: spiral-shaped, “_____spirella”; subset of these called spirochetes that have a very flexible twist in them
Bacteria Classification by Temperature (3)
- psychrophiles: cold temp
- mesophiles: medium temp
- thermophiles: hot temp
What is a bacteria cell wall made of?
peptidoglycan (combination of amino acid + sugar)
What are auxotrophs?
- type of bacteria that can’t do something
- “arg-“ then can’t make arginine
- “leu-“ then can’t make leucine
- “lac-“ then can’t metabolize lactate
- amino acids = can’t make*
- sugars = can’t metabolize*
Obligate Aerobe
- bacteria
- O2 present: can survive, can carry out aerobic metabolism
- O2 absent: can’t survive, can’t carry out anaerobic metabolism
Facultative Anaerobe
- bacteria
- O2 present: can survive, can carry out aerobic metabolism
- O2 absent: can survive, can carry out anaerobic metabolism
Obligate Anaerobe
- bacteria
- O2 present: can’t survive, can’t carry out aerobic metabolism
- O2 absent: can survive, can carry out anaerobic metabolism
Aerotolerant Anaerobe
- bacteria
- O2 present: can survive, can’t carry out aerobic metabolism
- O2 absent: can survive, can carry out anaerobic metabolism
What structures does a prokaryotic cell contain?
- cell wall
- flagella
- plasma membrane
- plasmids
Cell Wall
- provides structure and controls movement of solutes
- two main types found in bacteria: gram-positive and gram-negative
Gram-Positive Cell Wall
- envelope absorbs violet stain and appears deep purple
- has a thick cell wall composed of peptidoglycan (amino sugars put together)
Gram-Negative Cell Wall
- does not absorb violet stain but envelope absorbs safranin counterstain which makes it appear pink-red
- thin wall with small amounts of peptidoglycan
- cell wall is separated from the cell membrane by the periplasmic space
- tend to be more antibiotic resistant
- carbohydrates and lipopolysaccharide (carbohydrate linked to membrane by a lipid) are found on the outer membrane
What part of gram-positive bacteria triggers an immune response in humans?
lipoteichoic acid
What part of gram-negative bacteria triggers an immune response in humans?
lipopolysaccharides
Flagella
- used to propel bacteria
- allow a cell to detect chemical stimuli and move toward or away from the stimuli (referred to as chemotaxis)
- composed of: filament (hollow, helical structure made of flagellin), basal body (anchors flagellum to cytoplasmic membrane, motor), hook (connects filament and basal body, causes rotary movement)
Plasmids
- small circular structures that carry DNA acquired from external sources
- external DNA is not necessary for survival of prokaryote
What subunits are found in prokaryotic ribosomes?
30s and 50s subunits
Binary Fission
- simple form of reproduction seen in prokaryotes
- leads to big increase in population size but no change in genetic diversity
- proceeds rapidly
Describe the 2 steps of binary fission
- circular chromosome attaches to cell wall and replicated while cell grows in size
- plasma membrane and cell wall grow inward along midline of cell (invagination) to produce two identical daughter cells
What are plasmids?
- involved in genetic recombination
- extrachromosomal material found in bacteria
- often carry genes that can benefit the bacterium – genes for antibiotic resistance
What are virulence factors?
- involved in genetic recombination
- traits that increase how pathogenic a bacterium is
- includes: toxin production, projections that allow bacteria to attach to cells, evasion of host’s immune system
What are episomes?
- involved in genetic recombination
- subset of plasmids capable of integrating into the genome of bacteria
What is a vector?
- involved in genetic recombination, specifically transduction
- virus that carries genetic material from one bacterium to another
What are bacteriophages?
- involved in genetic recombination, specifically transduction
- viruses that infect bacteria
What are the different processes of recombination?
- transformation
- conjugation
- transduction
- transposon
Transformation
- results from integration of foreign genetic material into host genome
- foreign genetic material usually comes from other bacteria that spill their contents in the general vicinity via use of gram-negative rods
Conjugation
- leads to a big increase in genetic diversity without change in population size
- bacterial form of sexual reproduction
- use of a donor male (F+) and a recipient female (F-)
- allows for rapid acquisition if antibiotic resistance or virulence factors throughout a colony
Donor Male (F+)
- contains F (fertility) Factor (common plasmid that is a sex factor and contains necessary genes)
- forms the conjugation bridge (made from appendages called sex pili) which facilitates unidirectional transfer of genetic material to recipient female
Recipient Female (F-)
- accepts genetic material from donor male
- does not contain sex factors that are necessary to form the pilus
Transduction
transfer of genetic material from one bacterium to another using a bacteriophage as a vector
Transposons
genetic elements that are capable of inserting and removing themselves from the genome
What are the phases of bacterial growth?
- Lag
- Exponential
- Stationary
- Death
Describe the features of the Lag Phase
- bacteria get used to environment
- little growth during this time
Describe the features of the Exponential Phase
- bacteria use available resources to multiply at an exponential rate
- time of great growth
Describe the features of the Stationary Phase
- resources are used up
- bacterial multiplication ceases
- reached at carrying capacity
Describe the features of the Death Phase
- bacteria die as resources become insufficient to support the colony
- large decrease
Are ribosomes organelles?
NO
Cilia
- often found on prokaryotes
- hairs that wave back and forth for motility
Are cell walls unique to Prokaryotes?
No – all prokaryotes have these but some eukaryotes do too (Ex. plants, fungi)
What are the 2 amino sugars found in peptidoglycan?
- N-acetyl glucosamine
2. N-acetylmuramic acid
What are the specialized coverings found on prokaryotic cells?
- capsule (resistant, protects bacteria from immune system)
- slime layer (easily slips off bacteria, allows bacteria to escape from harm)
Bacteria have ___ growth
exponential
Symbiotic Relationship
- both bacteria and host benefit from interaction
- ex. gut bacteria get nutrients from food we eat while bacteria digest some nutrients that we can’t
Chemotaxis
-bacteria “senses” a chemical and can either move towards it or away from it
