concept 27.2
TRANSCRIPT
Concept 27.2: A great diversity of nutritional and metabolic adaptations
have evolve in prokaryotes
Alex, Maya, Michelle
Nutritional diversity is greater in prokaryotes than eukaryotes
Phototrophs-organisms that obtain energy from light
Chemotrophs-those that obtain energy from chemicals
Autotrophs-organisms that only require CO2 as a carbon source
Heterotrophs-organisms that require at least 1 other organic nutrient to make other organic compounds
Major Nutritional Modes
Photosynthetic organisms Capture light energy and use it to drive the
synthesis of organic compounds from CO2
Ex: Cyanobacteria, plants and algae
Photoautotrophs
Also only require CO2 as a carbon source and oxidize inorganic substances like ammonia, hydrogen sulfide
Mode of nutrition unique to certain prokaryotes
Ex: Sulfolobus
Chemoautotrophs
Use light energy but must get carbon in an organic form
Used by some marine prokaryotes Ex: Rhodobacter and Chloroflexus
Photoheterotrophs
Their energy source is organic compounds and they require organic carbon
Many prokaryotes, fungi, animals and some plants use this
Ex: Clostridium
Chemoheterotrophs
Obligate aerobes: use O2 for cellular respiration—cannot grow without it
Facultative anaerobes: use O2 if present but can grow by fermentation in an anaerobic environment
Obligate anaerobes: poisoned by O2; some live exclusively by fermentation
Metabolic Relationships to Oxygen
Other obligate anaerobes extract chemical energy by anaerobic respiration—substances other than O2 accept electrons at the “downhill” end of electron transport chain
Cont.
Some prokaryotes convert atmospheric nitrogen (N2) to ammonia (NH3)
This ‘fixed’ nitrogen is incorporated into amino acids and other organic molecules
Nitrogen Metabolism
Cooperation: working together Some proks can’t use resources by
themselves◦ No specialized organelles!
Cooperation between specialized cells Exchange of metabolic products
Metabolic Cooperation
Ex. Cyanobacteria Anabaena can photosynthesis + nitrogen fix Photosynth. produce O2, inactives nitrogen fixing
enzymes Live in colonies Most carry out photosynth., others nitrogen fix Heterocytes = “other cells” (nitrogen-fix) Heterocytes surrounded by cell wall, inhibits O2 entry Transport between cells
FUNCTION OF CONCENTRATION GRADIENTS AND CELL SPECIALIZATION!!!!!
Example
Biofilm = surface-coat colonies w/ metabolic cooperation
Signaling molecules Channels between cells allow flow of
nutrients Other species can cooperate as well