Transcript The Cell Theory

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)
The world of prokaryotes
C. They’re everywhere!
•Collective prokaryote biomass outweighs all
eukaryotes combined by at least tenfold.
•They exist almost everywhere, including places where
eukaryotes cannot.
•Most prokaryotes are beneficial; we couldn’t live
without them. (e.g. Nitrogen-fixing bacteria)
Lyme disease:
Caused by a spirochete
•Some cause illness  bubonic plague, diphtheria,
salmonella
•Approximately 5000 species have been
identified. Estimates of prokaryote diversity range from
400,000 to 4,000,000 species.
D. Bacteria and Achaea are the two main branches of
prokaryote evolution
Achaea are thought to be more closely related to
eukaryotes than to bacteria.
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 nucleoid region 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.
Specialized membranes of prokaryotes
nucleoid
N
Prokaryotic cells
Diagram
Components
of a prokaryote
 Cytoplasm
 Ribosomes
 Nuclear Zone
 DNA
 Plasmid
 Cell Membrane
 Mesosome
 Cell Wall
 Capsule (or slime layer)
 Flagellum
Gram Positive
Peptidoglycan
Plasma membrane
Gram Negative
Lipopolysaccharide layer
Outer membrane
Peptidoglycan
Plasma membrane
PROCARYOTES
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
2. Chlamydias
- Parasitic; survive only within cells of
animals
- Some cause STDs e.g. Chlamydia
3. Spirochetes
- Helical heterotrophs
- Some cause STDs e.g. syphilis
Mycoplasma shown covering a human cell; some species of mycoplasmas
cause walking pneumonia
5.
Cyanobacteria
- 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!
53.10
Humans use prokaryotes in research and technology
Examples:
Sewage treatment
Bioremediation
Chemical & Medical production
Research (genetic engineering, etc.)
Eukaryotic and
Prokaryotic Cells
Prokaryote = without a nucleus
Eukaryote = with a nucleus
EUKARYOTE
Diagram
Components of a Eukaryote
 Cytoplasm
 Nucleus with Nucleolus
 Mitochondria
 Chloroplast
 Ribosomes
 Rough Endoplasmic Reticulum
 Smooth Endoplasmic Reticulum
 Golgi body
 Vacuoles
Components of a Eukaryote
continued
 Lysosomes
 Cytoskeleton
 Centriole
 Cilium and Flagellum
 Microvillus
 Cell membrane
 Cell Wall
Comparing Prokaryotic and Eukaryotic Cells
Prokaryotes
Eukaryotes
Have Organelles
Are mostly bacteria
Have cell wall
or membrane
Have DNA
Have cytoplasm
Have a
nucleus
Include all
plant and
animal cells
Have membranes
surrounding
organelles
Summary of the differences!
Prokaryotic Cells
Eukaryotic cells
small cells (< 5 mm)
larger cells (> 10 mm)
always unicellular
often multicellular
no nucleus or any membrane-bound
organelles
always have nucleus and other
membrane-bound organelles
DNA is circular, without proteins
DNA is linear and associated with
proteins to form chromatin
Ribosomes are small (70S)
Ribosomes are large (80S)
no cytoskeleton
always has a cytoskeleton
cell division is by binary fission
cell division is by mitosis or meiosis
reproduction is always asexual
reproduction is asexual or sexual