Lecture 3 Flashcards
**Why does the species definition for sexually reproducing eukaryotes not apply well to Bacteria and Archaea?
binary fission
-Different species can’t produce fertile offspring Reproductive isolation
**What is the basis for the current species definition for Bacteria and Archaea?
Based on comparison of gene or genome sequences
• E.g. >95% average identity between two genomes
• >98.7% identity of 16S rRNA genes
• 70% DNA/DNA hybridization
Which of the eukaryotes that this class covers are always unicellular, always multicellular, or may be unicellular or multicellular?
always unicellular= protoza
always multicellular=helminths
may be unicellular or multicellular= fungi/algae
What component of the eukaryotic cytoplasmic membrane is largely absent in Bacteria and Archaea?
Contains sterols to strengthen membrane and maintain shape in absence of cell wall (some bacteria w/o wall have these too)
What are some components of the eukaryotic cytoplasm that are absent in Bacteria and Archaea?
Cytoplasm: more complex than prokaryotes; presence of organelles
- Site of translation
How are eukaryotic flagella similar to and different from bacterial(prokaryotic) flagella?
prokaryotic and eukaryotic flagella differ greatly in protein composition, structure, and mechanism of propulsion. However, both are used for swimming.
- bacterial: larger, more complex, bending movement, ATP driven
- eukaryotic: smaller/simpler, rotary, proton driven
• What are four steps in phagocytosis, and what role does the lysosome play?
Engulfment of particle
- Formation of vacuole
- Merging of vacuole with lysosome
- Digestion of particle
Lysosome contains digestive enzymes and low pH (acidic) containing digestive enzymes
What types of cells can perform phagocytosis (i.e. bacterial, archaeal, and/or eukaryotic)?
This process only occurs in eukaryotic
cells, not in Bacteria or Archaea (as far as
we know), and is enabled by their complex
cytoskeletal structure and machinery
What are the functions of mitochondria and chloroplasts?
Mitochondria: membrane-bound organelles, site of respiration
Chloroplasts: Site of photosynthesis (mainly plants, algae)
What is the endosymbiotic theory of the origin of these organelles, and what evidence supports the endosymbiosis theory?
Endosymbiosis theory: origin of mitochondria and chloroplasts
-Evidence for this includes many similarities between mitochondria/chloroplasts and
bacteria at the functional, structural, and molecular level
Endosymbiosis: Theory for the origin of eukaryotes that involved an ancestral proto-eukaryote engulfing smaller prokaryotic cells that became the mitochondria
and chloroplast organelles.
SLIDE 22,23,24
Are all fungi heterotrophic?
YES TRUE All fungi are heterotrophic: they “eat” (get their carbon and energy)
from organic substrates…
• Saprobes: substrates are dead, decaying plant/animal remains
• Parasites: substrates are living organisms
What is Endosymbiosis
Theory for the origin of eukaryotes that involved an ancestral proto-eukaryote engulfing smaller prokaryotic cells that became the mitochondria
and chloroplast organelles.
What is the difference between a saprobe and a parasite?
Saprobes: substrates are dead, decaying plant/animal remains
• Parasites: substrates are living organisms
What are two major fungal cell types?
-YEASTS have an oval shape (chains are called pseudohyphae) -HYPHAE are long, thread-like (filamentous) cells • May or may not possess barriers (septa) between cells
What is a mycelium?
Masses of hyphae in mold
colonies
What are some similarities and differences between fungal and bacterial cell walls?
SLIDE 28
Doesn’t contain peptidoglycan …but similar in structure (glycans, peptides/proteins) and function (provides rigidity, prevents osmotic lysis) to bacterial cell walls
What is the difference between sporangiospores and conidiospores?
Sporangiospores are contained within a sac (sporangium) • Conidiospores are not sac enclosed but are produced at cell tips or sides (Different structures involved in asexual spore formation in molds (hyphal fungi))
What are the main functions of fungal spores, and how does this differ from bacterial endospores?
Fungal spores are mainly for
reproduction and dispersal, and
are not as resistant as bacterial
endospores
What is an endospore?
a resistant asexual spore that develops inside some bacteria cells.
the inner layer of the membrane or wall of some spores and pollen grains.
What is the difference between endoplasm and ectoplasm, and in what type of microbial eukaryote are these two distinct regions typically found?
Ectoplasm: Involved in movement and feeding
• Endoplasm: Contains nucleus, ribosomes,
mitochondria
-protozoa
What is a general environmental requirement of most protozoa?
Protozoa are generally heterotrophic, consuming dead plant/animal material or bacteria ***Most protozoa require moisture, and form dormant cysts in dry conditions or lack of nutrients (encystment).
What are some differences between trophozoites and cysts, and what roles to these forms play in the protozoan life cycle?
***Cysts help protozoa survive desiccation, extremes of pH, and low nutrients. Some
cysts are also important reproductive stages or are involved in transfer between
hosts
trophozoite
(feeding, active form) and cyst (dormant) forms
cilia in eukaryotes
Cilia: typically smaller/shorter, more numerous than flagella
• Also can be involved in motility, feeding, interaction with objects
How do cysts compare to bacterial endospores in terms of resistance to environmental stresses?
Cysts are more resistant than trophozoites to heat, drying, an chemicals(but not as resistant as endospores)
What are four major groups of pathogenic protozoa, grouped by motility type and/or morphology?
Amoeboid -E.g. Naegleria Motility by pseudopods Ciliated - Motility by cilia (if motile) - Flagellated - E.g. Giardia, Leishmania - Motility by flagella - Apicomplexan - E.g. Plasmodium, Cryptosporidium - May be non-motile or have gliding motility
pathogenic protozoa: Amoeboid
-E.g. Naegleria
Motility by pseudopods
pathogenic protozoa Ciliated
- Motility by cilia (if motile)
- Flagellated
- E.g. Giardia,
pathogenic protozoa Leishmania
Motility by flagella
- Apicomplexan
pathogenic protozoa Cryptosporidium
May be non-motile
or have gliding motility
How do helminths compare to prokaryotes and unicellular eukaryotes in terms of complexity?
multicellular and morphologically complex - Different organs/tissues - Can have separate male/female sexes, or can be hermaphroditic - Adult forms are often not microscopic - Eggs/transmissible forms are microscopic
What is the difference between the definitive and secondary/intermediate host for helminths?
Definitive host: where mating and adulthood occur - Secondary or intermediate host: where larval development occurs
• What types of cells can viruses infect? **
Viruses infect all types of organisms, including animals and plants, as well as bacteria and archaea.
Probably all organisms have viruses which infect them.
How does the number of viruses on Earth compare to the number of prokaryotic cells?
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• What name is used for viruses that infect Bacteria?
called phage or bacteriophage
• What sorts of activities do viruses perform outside of their host cells?
Spike proteins in the capsid or envelope bind to and facilitate entry into host cells
These help determine the host range of the virus
What does obligate intracellular parasite mean, and which types of viruses are obligate intracellular parasites?
Free virions are completely inert (with rare exceptions)-what does that mean?^
Do not replicate like cells: one virus can produce hundreds of viruses upon
successful infection of a host
• How does viral replication differ from replication of bacterial cells (and most other microbial cells)?
Viruses “hijack” cellular machinery (proteins) and therefore don’t need to encode many genes.
At a minimum they need to encode the viral capsid and “spike” proteins
HOWEVER, virus-specific genes, e.g. for replication or taking over a host cell, may also be encoded
What are two basic structures/components that all viruses contain?
Capsid, made of repeating protein subunits
Nucleic acid genome (may be DNA or RNA)
Together, the nucleic acid and protein capsid are called the nucleocapsid
What is a nucleocapsid?
Capsid, made of repeating protein subunits
Nucleic acid genome (may be DNA or RNA)
• What are spike proteins?
Spike proteins in the capsid or envelope bind to and facilitate entry into host cells
Where are they found on a virus, and what role do they play in the viral replication cycle and in determining the host range of a virus?
Adsorption, or binding, of the virus to the host cell. “Spike” proteins on the virus envelope (or protein coat) recognize specific receptors on the host cell surface.
What is the composition and origin of a viral envelope?
Derived from the host cell cytoplasmic membrane
Additional proteins present within/on the capsid or in the envelope
Do all viruses contain envelopes?
SOME
• How do viral genomes compare to those of cellular genomes, in terms of their size and diversity of composition?
Viral genomes are typically very small compared to cellular genomes.
Viruses “hijack” cellular machinery (proteins) and therefore don’t need to encode many genes.
• What are five major steps in the replication (life) cycle of a virus (using an animal cell virus as an example, Table 5.4 in textbook)? What occurs during each of these steps?
Adsorption, or binding, of the virus to the host cell. “Spike” proteins on the virus envelope (or protein coat) recognize specific receptors on the host cell surface.
Penetration into the cell and uncoating of the viral nucleic acid
Synthesis of viral nucleic acid and viral proteins; achieved by disruption of normal cellular processes and diversion to viral synthesis
Assembly of virions
Release of virions from the cell
• What are two major modes of viral entry into animal cells, and which of these can be used by both enveloped and naked viruses?
Engulfment can be used for both enveloped and naked viruses
Fusion can only be used for enveloped viruses (requires fusion between envelope and host cytoplasmic membrane)
• What are five major stages in the lytic cycle of a bacteriophage? (Note the similarities to life cycle of animal viruses, i.e. these are five general steps in the infection cycle of all viruses).
- adsorption
- penetration
- synthesis (virus “hijacks” host machinery”
- assembly and maturation of new virions
- host cell lysis and release of new virions
What is the difference between lytic and lysogenic (or temperate) bacteriophage? What occurs during the lysogenic state?
Lytic bacteriophage: Can only go through lytic cycle
Lysogenic (or temperate) bacteriophage: Can either go directly to lytic cycle or can enter lysogenic state
• Be able to identify major differences in the function and structure of 1) eukaryotic cells, 2) prokaryotic cells, and 3) viruses.
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