Lecture 21 - Prokaryotes 1 (SI) Flashcards
Cell wall
- maintains cell shape
- protects cell
- prevents it from bursting (hypotonic)
Chitin
makes up fungal (+heliozoa) cell walls
Cellulose
makes up plant cell walls
What is archae cell wall composed of?
- polysaccharides
- proteins
Peptidoglycan
- cross-linked sugar polymers
- make up bacteria cell walls
- targeted by antibiotics
_____ contains a lot of peptidoglycan and ______ contains little peptidoglycan
- gram pos. contains a lot
- gram neg. contains little
Which type of bacteria tends to be more toxic/pathogenic?
gram negative
Capsule
-polysaccharide or protein layer covering most prokaryotes
Nucleoid
chromosomal region in prokaryotes
Endospore
- original cell produces copy of its chromosomes
- surrounds that copy with tough multilayered structure
Plasmids
- smaller rings of DNA scattered throughout prokaryotic cells
- R carries resistance quality
What do fimbriae do?
-allow them to stick to their substrate + other individuals in a colony
Pili
- longer than fimbriae
- allow prokaryotes to exchange DNA
Flagella
- scattered on surface
- spin for propulsion
Convergence
evolved independently in each domain
Exaptation
- bacterial model composed of motor + hook + filament
- from ancestral secretory system
What is the order of structures of a gram-neg. bacteria from outside to in?
- capsule
- membrane composed mostly of lipopolysaccharide
- peptidoglycan
- membrane composed mostly of phospholipids
What are 3 key features of prokaryote reproduction?
- prokaryotes are small (.5-5mm)
- short regeneration time (except endoliths)
- binary fission
3 reasons why prokaryotes have rapid evolution?
- exchange of genetic material
- short generation times
- large populations
What are endoliths?
- organisms that live inside rocks + between mineral grains
- chemoautotrophs
- reproduce maybe once per century
What is genetic recombination?
- combining DNA from 2 sources
- contributes to diversity
Conjugation
- DNA is transferred between 2 prokaryotic cells (usually of same species) that are temporarily joined
- bacteria, DNA transfer always one way
- cell donates DNA, other receives it
F factor
- presence of this particular piece of DNA determines ability to form pili
- donate DNA during conjugation
R plasmid
- carry genes for antibiotic resistance
- fraction of bacteria with genes from resistance increase in population exposed to antibiotics
Transduction
-gene movement between bacteria by bacteriophages
Transformation
-change in genotype and phenotype due to assimilation of external DNA by a cell
What are the 4 major modes of nutrition
- photoautotrophy
- chemoautotrophy
- photoheterotrophy
- chemoheterotrophy
Photoautotroph
(autotroph)
E source: light
C source: CO2, HCO3 etc
EX: cynatobcteria, plants, algae
Chemoautotroph
(autotroph)
E source: inorganic chemicals
C source: CO2, HCO3 etc
EX: sulfolobus
Photohetertroph
(heterotroph)
E source: light
C source: organic compounds
EX: aquatic + salt-loving (Rhodobacter)
Chemohetertroph
(heterotoph)
E source: organic compounds
C source: Organic Compounds
EX: clostridium, many fungi/animals/plants
Nitrogen fixation
-convert N2 to ammonia
-essential for production of amino acids + nucleic acids
EX: anbaena
Obligate aerobes
require O2 for cellular respiration
Obligate anaerobes
- poisoned by O2
- use fermentation/anaerobic respiration
Facultative anaerobes
-survive with or without O2
What are heterocysts?
- photosynthetic cells + nitrogen fixing cells in Anabaena
- exchange metabolic products
What are taxis?
-ability to move toward or away from stimulus
What is an example of an extremophile bacteria?
- endollith
- grow very slowly
What are the two domains of prokaryotes?
- bacteria
2. arcahaea
Archaea are more closely related to ___ than ____
eukaryotes, bacteria
