concept 27.2

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