Prokaryotic cells and viruses Flashcards
What are the 2 main types of cells?
- Eukaryotic cells - Larger, have a nucleus and it’s bounded by nuclear membranes.
- Prokaryotic cells - Smaller, no nucleus or nuclear envelope.
Why can bacteria survive so easily?
Because they can adapt to almost all environment.
They are very successful in surviving due to their small size, normally 0.1-10um in length.
Name all the features of a bacteria.
- Capsule - A layer of slime outside of the cell wall. (only in some species).
- Cell Wall - Made up of murein.
- Cell-surface membrane.
- Plasmid - Small circular pieces of DNA (only in some species)
- Ribosomes - Smaller than eukaryotic cells.
- Cytoplasm - Jelly-like, contains enzymes and other soluble material.
- Genetic material - Large circle of free DNA.
- Flagellum - There may be more than one, used for locomotion (the ability to move from one place to another) (only in some species).
What is murein?
It’s the substance that makes up the bacteria’s cell wall, it’s a polymer of polysaccharides and peptides.
Many bacteria further protect themselves by secreting a capsule of thick slime around this wall.
What is inside of the cell wall of a bacteria cell?
- Cell-surface membrane and within the CSM is the cytoplasm which contains 70s ribosomes.
- These ribosomes are smaller than the ones in the eukaryotic cells (80s) but they still synthesis proteins.
How do bacteria store food?
It stores food as glycogen granules and oil droplets.
How are the genetic materials in bacteria appear as?
In the form of a circular strand of DNA. Separate from this are smaller circular pieces of DNA called plasmids.
They can reproduce themselves independently and may give bacterium resistance to harmful chemicals e.g. antibiotics.
What can a plasmid be used as?
They can be used as vectors (carriers of genetic information) in genetic engineering.
What is the role of the cell wall?
A physical barrier that keeps out certain substances and protects against mechanical damage and osmotic lysis. (bursting of the cell).
What is the role of the capsule?
Protects bacterium from other cells and help to stick groups of bacteria together for further protection.
What is the role of the cell-surface membrane?
Acts as a permeable layer that controls the 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 the plasmid?
Possesses the genes that may help the survival of bacteria in harmful conditions e.g. produces enzymes that break down antibiotics.
What are the key differences between a prokaryotic and eukaryotic cell?
P - No true nucleus, only an area where DNA is found.
E- Distinct nucleus, within the nuclear envelope.
P - DNA is not associated with proteins (pro).
E - DNA is associated with proteins called histones.
P - Some DNA may be found in circular forms called plasmids.
E - No plasmids, DNA is linear.
P - No membrane-bounded organelles.
E - Memebrane-bounded organelles e.g. mitochondria.
P - No chloroplast, only bacterial chlorophyll with the cell-surface membrane in some bacteria.
E - Chloroplast presents in plant and algae.
P - Ribosomes are smaller (70s)
E - Ribosomes are larger (80s)
P - Cell wall made of murein (peptidoglycan).
E - Cell walls are mostly made up of cellulose or chitin in fungi.
P - May have an outer layer of slime called capsule.
E - No capsule.
What are viruses?
They are acellular (not containing cells), non-living particles.
They are smaller than bacteria 20-300nm.
