Lecture 3 Flashcards
Explain what limits prokaryotic cell size.
lack compartmentalization, limited by the distance that molecules can diffuse within the cell
describe 4 different prokaryotice cell shapes
cocci (spheres) - O
bacilli (rods)
spherical (spirals)
viberious (comma shaped)
cell wall
Cell wall • Function? • Helps to maintain shape, provides physical protection, and prevents cell from bursting in hypotonic environment. • What are plant cell walls made of? • Cellulose • Fungi? • Chitin • Bacteria? • Peptidoglycan • Archaea • Lack peptidoglycan; variety of other polysaccharides and proteins.
Capsule
Capsule
• Sticky protective layer of polysaccharide and protein secreted outside the cell wall.
• Function:
• Adhesion to substrate or other individuals in a colony.
• Protection against dehydration and/or resistance to attack from host’s immune system
Fimbriae
Fimbriae (attachment pili)
• Hair-like surface protein appendages.
• Function: adhesion to one another or to substrate (or host).
Sex pili
Sex pili: longer than attachment fimbriae - used to
pull two cells together during conjugation
Endospore
some species can produce a tough thick-walled cells that can survive unfavourable conditions for long periods of time
Distinguish between the structure and staining properties of gram positive and gram negative cells
- Gram positive bacteria
- Simpler cell wall with large amount of peptidoglycan
- Thick peptidoglycan layer traps the stain crystal violet within the cytoplasm.
Gram negative bacteria
• More complex, with less peptidoglycan.
• Cell wall sandwiched between the plasma
membrane and an outer membrane.
• Outer membrane contains lipopolysaccharides.
Explain why gram staining is useful in medicine
can be used to quickly determine if an infection is due to gram negative or gram positive bacterium
Explain why Pathogenic gram negative bacteria are generally more resistant to antibiotics AND more deadly than pathogenic gram-positive bacteria.
Gram negative are more resistance because outer membrane impedes entry of drugs. Deadly because more resistance to antibiotics lipopolysaccarides are toxic and outer membrane resists host immune system
List 5 ways in which prokaryotes differ from eukaryotes in their internal and genomic structure.
1) lack compartmentalization
2) smaller genome 1/1000th as much DNA
3) lack nucleus
4) have singular circular chromosome with few associated proteins
5) have ribosomes that are smaller and differ in protein and RNA content
Describe pasmids
Some prokaryotes may have smaller rings of DNA called plasmids.
• Contain only a few genes for specialized functions; are not required under normal conditions.
• Replicate independently of main cellular chromosome
List 3 ways in which prokaryotes move.
1) flagella
2) Twitching and gliding by extending and retracting pili.
3) Cyanobacteria and other aquatic prokaryotes have gas vesicles to control buoyancy.
Define taxis
movement away or towards a stimulus
• e.g., moving towards oxygen and nutrients or away from toxic substances.
briefly explain how prokaryotic flagella differ from eukaryotiv flagella
Eukaryoes—> wip-like motor protein
Prokaryotes—> works like propeller
Differentiate between the following modes of nutrition discussed in this lecture and state which modes are exclusive to prokaryotes.
Photoautotrophs- organisms that use light energy to the synthesis of organic compounds from CO2
Chemoautotrophs: Organisms that use energy obtained from the oxidation of inorganic substances to drive the synthesis or organic compounds from CO2 (EXCLUSIVE PROKARYOTES)
Photoherterotrophs- use light energy to generate ATP, but obtain their carbon in organic form
(EXCLUSIVE TO PROKARYOTES)
Chemoheterotrophs- must consume organic molecules for both energy and as carbon source
Differentiate between obligate aerobes, obligate anaerobes, facultative anaerobes, and aerotolerant anaerobes.
Obligate aerobes- use O2 for cellular respiration and cannot grow without it… no other options
Obligate anaerobes- poisoned by O2 live exclusively by fermentation or anaerobic respiration, substances other then O2 as final electron acceptor
Facultative anaerobes- Use O2 when present, but are capable of switching to fermentation or anaerobic respiration in absence of O2
Aerotolerant anaerobes- do not use O2 but are not poisoned by it, obtain energy via anaerobic respiration, using final e- acceptor other than O2 at end of ETC
Differentiate between oxygenic photosynthesis and anoxygenic photosynthesis
What is the ultimate source of electrons in photosynthesis by plants?
• Water –> produces oxygen as by-product
= Oxygenic photosynthesis
Example prokaryote that carries out this type of photosynthesis?
(hint: history of life…crucial event…) cyanobacteria
• Some prokaryotes use molecules other than water as the source of electrons for photosynthesis.
• e.g., H2S, Fe2+
–> by-products are sulfur and ferric iron.
= Anoxygenic photosynthesis
Explain the importance of nitrogen fixation by prokaryotes to life on Earth.
- Eukaryotes are very limited in the forms of nitrogen that they can use; cannot use N2
- Prokaryotes can obtain nitrogen in a wide variety of forms, including N2
- Cyanobacteria and some archaea (methanogens) can convert N2to NH3 via nitrogen fixation.
- The “fixed” nitrogen can then be incorporated into amino acids and other organic molecules.
Explain how the cyanobacterium Anabaena cooperates to use environmental resources.
Anabaena (cyanobacterium)
• Can carry out photosynthesis and nitrogen fixation, but not both in a single cell.
• Forms colonies - majority of cells carry out photosynthesis; a few specialized cells (heterocysts or heterocytes) carry out nitrogen fixation.
Describe “biofilm” and provide an example of a beneficial and harmful consequence of biofilm.
Biofilms
• Surface-coating colonies.
• Secrete proteins that glue adjacent cells together and to substrate.
• Helps community of cells to remain in favorable location for growth.
• -ve: Contribute to tooth decay, accumulate in
pipelines —> damage
• +ve : Help stabilize and enrich sand and soil
Explain how pathogenic bacteria communicate and the advantage of communicating (what does it allow them to do?)
Bacteria “talk” to each other via a chemical
language = “quorum sensing.”
• In infectious bacteria: is used to coordinate attacks on host and evade immune system.
• Upon entering host, bacterial cells “sit and wait” – release chemical communication molecules into environment.
• Chemical binds to specific receptor on bacterial cell’s surface.
• Allows bacteria to count how many other bacterial cells are present in population.
• Once amount of molecule in environment reaches a certain amount, indicating a certain population size, the cells all launch an attack on the host together!
• Increases success of bacteria against host.
• Each species produces a very specific molecule, allowing for intraspecies communication….but bacteria are also multilingual!
• Also have a generic system - a universal language “spoken” by all bacteria.
• Allows bacteria to count how many of other species are present, and behave accordingly.
Very briefly describe the process by which a prokaryotic cell reproduces
• Prokaryotes are highly successful because they
have the potential to reproduce VERY quickly in
favorable environments.
• Reproduce via binary
fission.
Explain the connection between botulism and endospores.
endospores allow cells to survive unfavorable conditions so botulism occurs when endospores allow bacteria to remain on food despite heat or other conditions that would normally eliminate them
