3.6 Prokaryotic cells and viruses Flashcards
What are the main features of a bacterial cell?
- Cell wall
- Capsule
- Cell-surface membrane
- Circular DNA
- Plasmid
What is the role of the cell wall?
A physical barrier which excludes certain substances and protects against mechanical damage and osmotic lysis.
What is the role of the capsule?
Protects bacterium from other cell sand helps groups of bacteria to stick together for further protection.
What is the role of the cell-surface membrane?
Acts as a differentially permeable layer, which controls entry and exit of chemicals.
What is the role of circular DNA?
Possesses the genetic information for the replication of bacterial cells.
What is the role of a plasmid?
possesses genes which aid the survival of the bacterium in adverse conditions.
What are the features of prokaryotic cells?
- no true nucleus, only an area where DNA is found.
- DNA is not associated with proteins
- some DNA is in circular form (plasmids)
- no membrane-bound organelles
- no chloroplasts, only bacterial chlorophyll
- smaller ribosomes- 70S
- murein cell wall
- may have an out layer of slime
What are the features of eukaryotic cells?
- distinct nucleus and envelope
- DNA is associated with histone proteins
- Linear DNA
- membrane-bound organelles
- chloroplasts in plants and algae
- larger ribosomes- 80S
- cellulose or chitin cell wall
- no capsule
What is a virus?
a non-living, acellular particle reliant on host cells to multiply.
Describe the structure of a virus.
- contain NUCLEIC ACIDS (DNA or RNA)
- nucleic acids are held in a PROTEIN COAT called a CAPSID
- some viruses have a lipid envelope
- on either the lipid envelope or the capsid are attachment proteins
