1- Cell Biology Flashcards
Key Facts about bacteria
- Bacteria are prokaryotic
- Don’t have a nucleus, mitochondria or chloroplasts like eukaryotes
- Much smaller (10-100x smaller) than eukaryotes
How fast can some bacteria divide?
As often as once every 20 minutes
What is the name of bacterial replication?
Binary fission
What does the speed of bacterial replication depend on?
Temperature and enough nutrients
What is the process of binary fission?
- DNA is replicated (DNA loop and plasmids)
- Organelles e.g. ribosomes double in number
- The cytoplasm divides
- A new cell wall forms around the daughter cells
- These daughter cells are genetically identical to the mother cell. This is asexual reproduction
What are the two ways bacteria be grown in a lab?
- Agar plate
- Nutrient broth
Where do bacterial colonies come from?
One parent bacterium- they are all clones of each other
What is aseptic technique?
The methods that are used by scientists to prevent contamination of the agar or nutrient broth with unwanted microorganisms
A student is told to grow some bacteria on an agar jelly in a Petri dish.
Describe how the student should prepare an uncontaminated culture of the bacterium in the Petri dish.
You should explain the reasons for each of the steps you describe.
Pre-inoculation
- Petri dish and agar sterilised before use (Allowed surfaces)
- to kill unwanted bacteria
- inoculating loop passed through flame / sterile swab
- to sterilise / kill (other) bacteria
Inoculation
- loop/swab used to spread / streak bacterium onto agar
- lid of Petri dish opened as little as possible
- to prevent microbes from air entering
Post-inoculation
- sealed with tape
- to prevent microbes from air entering
- incubate
- to allow growth of bacteria
What equation is used to calculate the number of bacteria at the end of a growth period?
Bacteria at the end of the growth period = Bacteria at the start of the growth period x 2 to the power of the number of divisions
