T9 - Prokaryotes Flashcards
What is a paraphyletic group vs a monophyletic group?
Para = Have the common ancestor but not all the descendants from the ancestor
Mono = common ancestor and includes all the descendants
What group are prokaryotes considered as?
Paraphyletic group, includes the common ancestor (LUCA - likely a prokaryote) and some of its descendants (excluding eukaryote)
What are some characteristics of prokaryotes?
- plasma membrane which constitutes a selective barrier with the environment (preventing the entry of some molecules)
- cytoplasm = content of the cell within the plasma membrane is made of cytosol (internal fluid containing organic molecules, proteins, metabolic waste)
- absence of a nucleus = circular chromosome located in the nucleoid (region not enclosed by a membrane)
- Fimbriae = short appendages helping bacteria to adhere to the substrate or to other cells
- Capsule = dense layer of polysaccharide or protein surrounding the cell wall - protects the cell and allows the bacteria to adhere to substrates or cells
- absence of organelles (only exist in eukaryotes)
Describe some characteristics of bacteria
- Lacks histones (proteins that bind to the DNA and play a key role in packaging of genome) but are present in some archaea
- protective cell wall made of peptidoglycan in bacteria
- Flagellum = long cellular appendage specialized for locomotion
- Taxis = directed movement towards or away from a stimulus - may detect light/food which will lead it towards it because of attraction
What are the classifications of different organisms based on their carbon source and energy source ?
Energy source;
- Light = phototrophs
- Chemical compounds = chemotrophs
Carbon source
- (light) Inorganic compound = photoautotroph
- (light) organic compound = photoheterotroph
- (chem) inorganic compound = chemoautotroph
- (chem) organic compound = chemheterotroph
What is the role of prokaryotes in the ecosystem?
Food webs depend on primary producers (those that release oxygen and are at the base of the ecosystem)
1) Absorbing energy from outside the ecosystem (sunlight)
- photoautotrophs can; convert CO2 into sugars to enter the food chain
- produce O2 ued by chemoheterotroph (respiration)
- fix atmospheric N2 and produce proteins/nucleic acids
2) Assimilating minerals into biomass that is passed on upper tropic levels
- decomposers absorb and convert nutrients from nonliving organic material (corpses, dead plants) into inorganic forms
- recylcing of C, H, O, N, P between the biotic and abiotic world
What is reproduction by binary fission?
aka cell division = doubling in size and simple division in half (this is not mitosis)
- requires the replication of the genome initiated at the origin of replication
- two daughter cells are teh clones of the mother cell
- follows exponential growth provided there are enough resources
What are the different phases of binary fission?
- Lag phase = synthesis of components required for growth
- Log phase = rapid growth through cell divisions by a factor of 2^n where n = number of generations
- Stationary phase = population stops to grow and there is an activation of stress response (due to lack of nutrients, oxygen or metabolic waste accumulation…)
- Death phase = exponential loss of viability due to lack of nutrients, oxygen or prolonged exposure to waste (stress has accumulated)
What is an antibiotic? how can bacteria evolve resistance to them?
Antibiotic = molecule that kills or inhibits the growth of bacteria
- Mutations can alter genes coding for proteins that are the target of antibiotic genetic (variation between bacterial strains)
- Resistance can be transmitted vertically through inheritance (heritability of the acquired resistance) - transmitted rom one generation to the next when time = vertical axis
- Only the resistant strains can grow (selection for resistance)
What is conjugation?
- two cells are temporarily joined through a pilus (hair like structure)
- there is an establishment of a mating bridge (direct contact)
- a plasmid (small circular chromosome) can be transferred from donor to receiverW
What is the F factor? R plasmid?
F factor (fertility factor) = contains genes required to make the pilus
- selfish DNA - dna that enhances its own transmission at the expense of the rest of the genome being transmitted
R plasmid = genes carried by this confer antibiotic resistance and can spread throug conjugation
- resistance plasmid which also contains genes coding for the sex pilus (like F factor)
