Cell Growth & Control Flashcards
Steps of binary fission
- DNA replication
- Cell elongation
- Septum formation
- Completion of septum with formation of distinct walls
- Cell separation
4 phases of prokaryotic growth
- Lag phase
- Exponential phase
- Stationary phase
- Death phase
What happens in the lag phase
- Cell prepare for growth
- Gene expression
- Synthesis of certain macromolecules
when does exponential phase occur
When cells are adapted to their environment & are growing optimally
In what phase do genetic/biochemical experiments occur at
The exponential phase
What is happening during the stationary phase
- No increase in cell mass/cell number
- Cell growth & death happening at the same time
What is stationary phase caused by
- Essential nutrient supplied by medium is exhausted
- Waste products from metabolism build up to inhibitory levels
Why does death phase occur
- Nutrients deplete
- Toxic metabolic waste products increase
Will serial dilutions differentiate between alive & dead cells
Serial dilutions will differentiate between alive & dead cells as only viable cells will grow
Natural human defences that control microbial growth
- Enzyme lysozyme in both tears & saliva
- Lysozyme cleaves peptidoglycan in bacterial cell walls
environmental effects on microbial growth (5)
- Nutrients
- Temp
- pH
- Water activity
- O2 availability
Max growth temperature
Temperature above which denaturation occurs
3 cardinal temperatures
- Max growth temp
- Min growth temp
- Optimum temp
Optimum temp
Enzymatic rxns occurring at maximal possible rate
Psychrophiles
Low temperature optima
