prokaryotes
single celled, no nuclei, includes eubacteria and archea (also called bacteria and arcbacteria)
eukaryotes
have nuclei, can be single or multicellular, includes plants, funghi, animals, humans
Example of a single celled eukaryote
yeast
Features of the prokaryotic cell
capsule - polysaccharide layer for protection from engulfment (optional)
cell wall - tough, protective outer coat (optional)
plasma membranes - surrounds all cells
DNA nucleoid - compact structure of DNA (NO NUCLEUS, but is still found in specific part of cell)
Which features are optional in prokaryotic cell (which ones are not present in all p. cells)?
Capsule and cell wall, flagellum and pilus
Ribosome
protein synthesis
flagellum
locomotion (not in all prokaryotes)
Pilus
two types:
- one for locomotion
- one for sexual conjugation
Eukaryotic cell
- 1000 times bigger than prokaryotic cell, which means it requires cytoskeleton for support
- has membrane bound organelles
- has mitochondria (powerhouse of cell, ATP generation)
- has nucleus
- has plasma membrane like prokaryotic
Features that plant cells have but animal cells don’t…
cell wall - for protection
chloroplast - for photosynthesis
vacuole - two types for storage and degradation (there are similar structures in animal cells but they’re called something else)
Two lines of evidence that show eukaryotes evolved from prokaryotes
fossil record - eukaryotes appear in record 1 billion years later after prokaryotes
structural similarity - share many complex traits that could not have evolved independently
Endosymbiont Theory
- Eukaryotic ancestor is a heterotrophic (cannot produce own food must take organic matter from environment) anaerobic (derived energy from food matter without molecular oxygen) cell
- mitochondrial ancestor was a free living, aerobic prokaryote able to use oxygen to help generate ATP that was engulfed by the larger heterotrophic aerobic cell and resisted digestion in cytoplasm
FECA
First Eukaryotic Common Ancestor
- gave shelter to mitochondrial ancestors in exchange for oxygen generated ATP
- nuclear membrane developed as symbiosis occurred
LECA
Last Eukaryotic Common Ancestor
- does not contain chloroplasts (last common ancestor between us and plants)
What was the key step in producing FECA?
Prokaryotic ancestors somehow acquired ability to form internal membranes and compartments. The key step towards FECA was the development of these membranes into closed internal compartments (which then allowed for production of nucleus to hold DNA).
Are internal membranes exclusively a eukaryotic trait?
No, some bacteria can have extensive internal membrane networks but they are NOT closed—they do not have membrane bound organelles like eukaryotes
Evidence for endosymbiont theory
- Some prokaryotes form simple internal membranes
- There are carnivorous single-celled eukaryotes which can phagocytosize (engulf) things - shows that the mechanism is plausible
- Mitochondria and chloroplast still have evidence of their own DNA - genome is circular and looks prokaryotic
- Both mitochondria and chloroplast have double membranes and their own ribosomes (remnant structures)
Where did Margulis propose chloroplasts came from?
Cyanobacteria. An early heterotrophic eukaryote acquired ability to photosynthesize.
Archea are prokaryotes but are in some ways…
more similar to eukaryotes.
How does the double membrane of mitochondria and chloroplast provide evidence for endosymbiont theory?
The internal and external membrane have different compositions. Possible that one originated from original anaerobic host cell and other from the host cell itself.
Cyanobacteria, Methanococcus, Methanobacteria
- capable of photosynthesis (PROKARYOTE)
- lives at hydrothermal vents at bottom of ocean (ARCHEA)
- lives in low pH, anaerobic conditions (cow stomach) (ARCHEA)
Difference between 19th/20th century method and 20th/21st century method of studying diversity?
Older approaches - collect more stuff and organize
Newer approaches - model organisms
Model organisms
- studied extensively over a long period of time
- have rapid development with short life cycles
- small adult size (can fit in lab)
- readily available
- tractability (ease of modification/manipulation)
- understandable genetics (DNA is not too complicated)
Central dogma
DNA –(transcription)–> RNA —-(translation)–> PROTEIN
