2. prokaryotic cells and viruses Flashcards
cytoplasm?
no membrane bound organelles (unlike eukaryote)
has ribosomes but smaller than in a eukaryote (70s vs 80s)
flagellum?
long hair like structure that rotates to make cell move
not all have a flagellum, some have more than 1
nucleus?
no DNA floats free in cytoplasm circular DNA (one coiled up strand) not attached to any histone proteins
plasmids?
small loops of DNA
not always present
contain genes for things like antibiotic resistance
can be passed between prokaryotes
plasma membrane?
yes
cell wall?
yes
supports cell prevents it changing shape. made of polymer murein (a glycoprotein - protein with carbohydrate attached)
capsule?
in some prokaryotes
made of slime
helps protect bacteria
viruses are
Acellular
nucleic acids surrounded by protein
not alive
how are viruses different to bacteria
smaller
have no plasma membrane, cytoplasm, ribosomes
why are viruses known as host cells
all viruses invade and reproduce inside cells of other organisms
structure of viruses
contain core of genetic material either DNA or RNA
protein coat around core is called capsid
attachment proteins stick out from edge of capsid letting viruses cling to suitable host
how to prokaryotic cells replicate?
by binary fission
how does binary fission work
- circular DNA and plasmids replicate. main DNA loop replicated once but plasmids can be replicated lots of times
- cell gets bigger and DNA loop moves to opposite poles of the cell
- cytoplasm begins to divide and new cell walls begin to form
- cytoplasm divides and 2 daughter cells produced. each daughter cell has one copy of DNA but can have variable copies of plasmids
how do viruses replicate
- use attachment proteins to bind to complimentary receptor protein on surface of host cells
- different viruses have different receptor proteins therefore require different host cells. as a result some viruses can only infect 1 type of cell
- not alive - don’t undergo cell division. inject DNA or RNA into host cell. the cell then replicates viral particles using its own organelles / proteins