Topic 7 - Prokaryotic and Viruses Flashcards
what are prions?
- prions are proteins that are misfolded relative to their normal structure.
- they are able to induce similar misfolding in proteins that they come in contact with. (They are able to reproduce themselves with error, but lack other features of being alive)
- a buildup of misfolded proteins can cause disease.
-prions from different species may induce disease if ingested; prions cannot be destroyed at normal cooking temperatures.
What is the first fossil evidence of life on earth of prokaryotes?
- For 2.5 billion years ago
what are the two domains?
- bacteria
- archaea
- only forms of life for 1.5 billion years.
Do prokaryotes dominate the biosphere numerically and are second to plants in total biomass?
True
where can prokayotes live?
- they live in places where eukaryotes do and many places they cannot, such as oil sands.
Prokaryotic Diversity
- the # of described species of prokaryote sis is much less than the number of described eukaryotic spp.
- the # of prokaryote species and higher taxa are increasing very rapidly due to DNA- and RNA-based descriptions.
-because of this rapid increase in names, it is
difficult to get a count of validly described taxa
- there are a total of 23865 valid spp. of prokaryotes.
how many phyla in domain bacteria?
40 phyla
how many phyla in domain archaea?
4 phyla
what is a prokaryote?
- organisms whose cells lack a nucleus and other organelles.
what is the first feature of prokaryotes?
- they do not have a nucleus.
- nucleus = membrane-bound organelle
containing genetic material structured as
dense linear chromosomes
-pro = first/before
- karyon = kernel (i.e.,
nucleus; nucle = little nut )
– eu = true
- instead have a diffuse, circular ring of
DNA not enclosed by membrane
– the nucleoid region
what is the second feature of prokaryotes?
- in addition to nucleoid regions, prokaryotes have plasmids.
-plasmids are small rings of DNA containing a few extra genes.
what is the third feature of prokaryotes?
- reproduction and transfer of genetic
material in prokaryotes take several
forms, none using mitosis or meiosis.
what are the different forms of reproduction?
- Binary Fusion:
- new DNA synthesized almost constantly
- when a chromosome duplicated, the cell splits
- new DNA synthesized almost constantly
-fission rate depends on the environment, can be divided once every 20
minutes
- Transformation:
- involves uptake of
‘naked’ DNA released from dead
prokaryote by a living prokaryote
- involves uptake of
- Transduction:
- involves the transport of
DNA between prokaryote cells by
viruses (bacteriophages [phag = eat]
and prophages)*
- involves the transport of
- Conjugation:
- when one
prokaryote latches on to another with
a string-like structure (called a pilus
in bacteria) and transfers DNA
i. One cell attaches its pilus to another and
then retracts it, pulling cells together
- when one
ii. transfer of genetic material in bacteria*
is unidirectional, from pilus-producer to
receiver
iii. plasmids are often transferred during conjugation.
what are transformation, transduction and conjugation are modes of?
- horizontal transfer of genetic material, and because of this antibiotic resistance can spread so rapidly.
what is horizontal?
- means
transfer between individuals
within the same generation - individuals need not be
related
what is vertical?
-means transfer
from parent to offspring
between generations
- e.g., binary fission
widespread use of
antibiotics has sped up
selection for —————— in most medically important bacteria.
resistance
what is the fourth feature of prokaryotes?
- bacterial cell wall.
- includes peptidoglycan (no cellulose in cell wall or chitin in fungi)
- archaeans lack peptidoglycan.
- cell wall prevents cell from exploding when
placed in hypotonic solution:
– hypotonic = lower in solutes than cell contents
(hypo = below); water enters cell [low solute out of cell, and high solute in cell] –> LYSIS
– hypertonic = higher in solutes than cell contents
(hyper = above, beyond); cell wall usually doesn’t
prevent plasmolysis, when water leaves cell [high solute out of cell, low solute in cell] –> SHRINK OR PLASMOLYZE
– (lys = release, usually in the sense of dissolve)
How does a bacterial cell wall determine whether the cell is Gram + or Gram -
- Gram + = have peptidoglycan wall in contact with
external medium which traps purple stain - Gram - = have lipopolysaccharide layer outside of cell
wall, and thus do not absorb stain readily - Gram - are more pathogenic, as out LPS layer can contain toxins also resist
action of antibiotics
what is the fifth feature of Prokaryotes?
- they lack membrane enclosed organelles.-no nucleus, mitochondria,
chloroplasts - however, prokaryotes may have structures that are highly complex.
what is the sixth feature of prokaryotes?
- prokaryotic smaller in size than eukaryotic cell.
- prokaryotic are 1-5 micrometre
- eukaryotic are 10-100micrometer.
what is the seventh feature of prokaryotes?
- many prokaryotic cells are motile, and they can move on their own.
- they use a g flagella (flagellum = whip)
- Prokaryotes perform taxes (plural) or taxis (singular)
- movement away from or towards stimulus
– e.g. positive phototaxis is movement towards
light (light receptor)
– note: motility and taxic behaviour not restricted
to prokaryotes
- movement away from or towards stimulus
Do prokaryotes differ from eukaryotes in
having a higher diversity of metabolic
pathways? (True or False)
True
what is metabolism?
-chemical pathways used by living organisms to build molecules (anabolism) or break down molecules to release energy (catabolism)
- meta = change
