Ch 17 Viruses and Bacteria Flashcards
describe viruses
- very, very small
- smaller than cells
- particles that cause diseases and sickness
who discovered and who named viruses
- discovered by Dimitri Iwanoski
- Named by Martinus Beijerinck
what are viruses
a noncellular particle made of genetic info and proteins that infects cells
who is responsible for helping to understand the nature of viruses
Wendell Stanley isolated a virus particle which lead to their nature being understood using an E- microscope
what is the structure of a virus
- core of nucleic acid, surrounded by a protein coat (capsid)
- Either RNA or DNA not both
- few genes
- bacteriophages are viruses that invade bacteria and have a tail and fibres
- Some are rods, cubes, tad pole shaped, or a variety of others
- 10-400 nanometers in size
why are viruses very specific
most viruses only infect certain organisms, certain target species specifically
what are the two types of virus lifestyle
Lytic and Lysogenic
describe lytic infection
- lytic viruses cause the host cell to lyse (burst) and release the new viruses
Infection: A virus touches a host cell by chance, and uses fibres to hold on while it injects DNA or DNA copy of RNA
Growth: after DNA was inject it can’t be distinguished from the host’s DNA so it is copied and mRNA is formed which shuts down the other cell operations
Replication: The materials of the cell are used to make more viruses which lyse out of the cell
- this process is called lytic infection
describe lysogenic infection
- Once the virus has infected it lies in wait, inserting it’s self into the DNA of the host
- Once there it is know as a prophage and may lie in wait for many generations
Prophage Activity
- can actually be helpful, blocking other viruses and making useful molecules. But after a certain time it will turn to a lytic infection due to various factors
what are retroviruses
- have RNA not DNA
- must make a DNA version of their RNA for insertion
what do scientists think of the origin of viruses
- developed after living cells as they need them to reproduce
- might have evolved from early bacteria
how are prokaryotes catogorized
- Eubacteria or Archaebacteria
- the two groups of bacteria
- range from 1-10 micrometers
- don’t have a nuclear envelope or organelle membranes
describe eubacteria
- larger group
- have a cell wall made of complex carbohydrates
- have flagella that they use for movement
- very diverse, many phylums
- some are simple, some are complex
- Cyanobacteria can photosynthesize but don’t have chloroplasts, found worldwide
- Prochlorobacteria can also photosynthesize, but are rare, green
describe archaebacteria
- lack a carbohydrate in the cell wall
- different lipids, ribosomes, and genes
- many extremophiles
- methanogens live in oxygen free environments and produce methane
describe the variation in bacterial form
cell shape: can be rods (bacilli), spheres (cocci), or spirals (Spirilla)
Can be found in pairs, chains, clusters, etc
Cell wall: can have 1 or 2 walls
bacterial movement: can have 1+ flagella, some lash, spiral, snake, some are inmobile
how can you identify how many cell walls a bacteria has
a method called gram (named after Christian Gram), staining can show how many legs of a cell wall an organism as
gram + = purple = 1 wall
gram - = red = 2 walls
what are the different ways bacteria obtain energy
Autotrophs:
- phototrophic autotrophs use the energy of the sun
- Chemotrophic autotrophs obtain energy from inorganic molecules like hydrogen sulfide
Heterotrophs:
- Take in organic molecules to breakdown, called chemotropic heterotrophs, they eat food
- phototrophic heterotrophs need energy from food but also use the sun
how do bacteria make the energy they need
the energy bacteria need is supplied by respiration and fermentation
what are the three types of relationship bacteria can have to oxygen
- Obligate Aerobes need oxygen
- Obligate Anaerobes are poisoned by oxygen
- Facultative Anaerobes don’t need oxygen but oxygen is not dangerous for them
how do bacteria reproduce
- bacteria can reproduce very quickly, some every 20 minutes
Binary Fission: Doubles in size, duplicated DNA, splits into two, asexual
Conjugation: a protein bridge is formed between two bacteria, one bacteria then gives the other some genes (sexual)
Spore formation: in unfavourable conditions bacteria can form spores, a self contain unit where the bacteria parts lay dormant until conditions are favourable (not technically reproduction)
why are bacteria important for us
- produce food
- digest petrol
- clean up waste and poison
- mine materials
- made drugs and chemicals
- can be symbiotic with other organisms (gut bio)
what roll do bacteria play in the environment
- nutrient flow: decompose dead organisms into good compounds
- sewage decomposition: break down sewage into simpler, useful compounds
- nitrogen fixation: bacteria take N2 and turn it into something plants can use
what can viruses do to people
viruses can attack human cells causing damage like small pox, polio etc
how can we deal with viruses
- preventing infection is important (vaccines Is good)
- the symptoms can be treated
