Lecture 2/3/4: Bacteria & Archaea Flashcards
(46 cards)
Which domain is prokaryote in?
Found in 2 domains of life:
1. Bacteria; e.g. E Coli
2. Archaea
Why is prokaryote in 2 domains of life?
Because the cells of Archaea and Bacteria lack a nucleus (definition of prokaryotes = cells lack a nucleus).
Define Prokaryotes
- organisms whose cells lack a nucleus and other organelles. - small, single-celled organisms that have simple structures.
- carry a small amount of genetic material
What are prokaryotic cells surrounded by?
a plasma membrane (but no internal membrane-bound organelles within their cytoplasm)
what is a plasmid?
small, circular DNA molecules that many prokaryotes carry. Different from chromosomal DNA (can provide genetic advantages in specific environments)
Where is the DNA in prokaryotes contained?
in a central area of the cell called the nucleoid (not surrounded by a nuclear membrane)
What are the 3 shapes of prokaryotes?
- Spherical
- Rod-Shaped
- Spiral
What is an example of a spherical shaped prokaryote?
Cocci (coccus = plural):
can occur singly, in pairs or in chains.
think cookie is shape of sphere
What is an example of a rod-shaped prokaryote?
Bacilli (bacillus = plural):
typically occur independently, can sometimes be found in chains
think banana is shape of rod
What is an example of a spiral shaped prokaryote?
Spirilla, range from comma-like to loose coils.
Spirochetes are corkscrew shaped
think spiral = spirilla
How are cell walls beneficial?
- maintains cell shape
- protects cell
- prevents it from bursting in a hypotonic environment
Do prokaryotic cells have a cell wall?
nearly all of them do, yes
Explain hypertonic
more salt outside of cell than inside, therefore water rushes outside of cell (to balance) = shrinkage
What are the results of a prokaryote losing water (hypertonic)?
water loss = inhibits reproduction
Explain hypotonic
means more salt on the inside of the cell than outside, therefore water rushes into cell (to balance) = swelling or even bursting of the cell
- better than hypertonic but could still be an issue
Explain isotonic
things are equal inside and outside of cell = BALANCED :)
What are the cell walls of plants and fungi made up of?
cellulose or chitin
What do most type of cells contain peptidoglycan (cross link of sugars)?
bacterial cells
What is peptidoglycan?
- tough protective wall that surrounds bacteria
- made up of sugars and proteins linked together
- helps keep their shape and stop from bursting when water tries to get in
- makes up most of the cell wall (especially gram positive bacteria)
- anchors other structures
What are archaeal cell walls made of?
other carbohydrates and proteins
- lacks peptidoglycan
What did Hans Christian Gram come up with?
- developed staining technique to classify bacteria into two groups
1. Gram Positive (purple)
2. Gram Negative (pink)
What colour is gram (+) after stained? What does the bacterium look like?
purple, spaced out and kinda larger
What colour is gram (-) after stained? What does the bacterium look like?
pink, closer together and kinda smaller
Which bacteria group (+ or -) has more peptidoglycan? Why?
Gram Positive (+); they rely mostly on this thick layer for protection which is why they have a lot of it.
