Prokaryotes vs. Eukaryotes. I. Structure, function, and reproduction of prokaryotes A . Most prokaryotes are unicellular. 1.Some species form aggregates of two or more individuals . B . Three (3) common shapes: cocci (round); bacilli ( rod); helical (spiral).
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Prokaryotes vs. Eukaryotes
I. Structure, function, and reproduction of prokaryotes
A. Most prokaryotes are unicellular.
1.Some species form aggregates of two or more individuals.
B. Three (3) common shapes: cocci (round); bacilli (rod); helical (spiral)
Caused by a spirochete
E. Most prokaryotes secrete sticky substances that form a protective layer and enable them to adhere to substrates.
1. The sticky protective layer secreted by prokaryotes is called the capsule.
2. Some prokaryotes adhere to substrates using Pili.(Pili are thin, protein tubes originating from the cytoplasmic membrane)
a. Some Pili are specialized for DNA transfer. This process is called conjugation; note for later in class.
F. Almost all prokaryotes have cell walls external to the plasma membrane.
1. Cell walls maintain cell shape.
2. Cell walls are composed of peptidoglycan.(a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of bacteria, forming the cell wall)
G. Cellular and genomic organization of prokaryotes is different from that of eukaryotes
1.Prokaryotes have no nucleus.
2. The nucleoidregion in a prokaryotic cell consists of a concentrated mass of DNA. This mass of DNA is usually one thousand times less than what is found in a eukaryote.
Photosynthesis evolved early in prokaryotic life
Cyanobacteria started to produce O2 about 2.7 billion years ago
Contrasting hypotheses for the taxonomic distribution of photosynthesis among prokaryotes.
Heliobacteria: Causes stomach ulcers
- Parasitic; survive only within cells of animals
- Some cause STDs e.g.Chlamydia
- Helical heterotrophs
- Some cause STDs e.g. syphilis
Mycoplasma shown covering a human cell; some species of mycoplasmas cause walking pneumonia
- Oxygenic photosynthesis, and chloroplasts evolved from them.
Ecological impacts of prokaryotes
A. Prokaryotes are links in the recycling of chemical elements
B. Many prokaryotes are symbiotic (2 organisms living in direct contact with each other).
Mutualism– both symbiotic organisms benefit
- e.g. Nitrogen-fixing bacteria like Rhizobium: plant obtain organic nitrogen, Rhizobium gets energy in the form of sugars that the plant produces.
Are all prokaryotes disease producing germs?
Without prokaryotes ecosystems would collapse!
Humans use prokaryotes in research and technology
Chemical & Medical production
Research (genetic engineering, etc.)
Prokaryote = without a nucleus
Eukaryote = with a nucleus
Comparing Prokaryotic and Eukaryotic Cells
Have membranes surrounding organelles
Have cell wall
Are mostly bacteria
Include all plant and animal cells