Prokaryotes and Viruses Flashcards
Compare the size and complexity of prokaryotic and eukaryotic cells:
Prokaryotic cells are smaller and simpler than eukaryotic cells.
T / F:
Bacteria are an example of a prokaryotic cell.
True.
Viruses are Acellular, what does this mean?
They are not cells, they are not alive. They are simply nucleic aids surrounded by protein.
Compare the size of bacteria and viruses:
They’re even smaller than bacteria - HIV is about 0.1 micrometre wide.
T / F:
Viruses contain a plasma membrane.
False.
What is meant by a host cell?
A cell which is invaded by a virus, and thus ‘hosts’ it.
Why are viruses seen like parasites?
Because they invade and reproduce inside the cells of other organisms.
T / F:
Viruses contain genetic material.
True.
T / F:
Viruses contain only DNA.
False, they can contain either DNA or RNA.
T / F:
Viruses contain a ribosomes.
False.
What are attachment proteins?
They stick out from the edge of the capsid. These let the virus cling onto a suitable host cell.
T / F:
Viruses contain either DNA or RNA.
True.
What is the capsid?
The protein coat which encapsulates a virus.
T / F:
Viruses contain only RNA.
False, they can contain either DNA or RNA.
T / F:
Viruses contain cytoplasm.
False.
How do prokaryotic cells replicate?
Binary Fission.
What happens during binary fission?
The cell replicates genetic material and then splits into two daughter cells.
Describe the cytoplasm of a prokaryotic cell.
It has no membrane-bound organelles, it does have ribosomes (small ones).
T / F:
Prokaryotic cells do not have a nucleus.
True - their DNA floats around, it is called circular DNA.
Which type of cell division in eukaryotes is more similar to binary fission?
Mitosis.
Where would the gene for antibiotic resistance be found in a prokaryotic cell?
In plasmids.
Describe the way which genetic information is stored in prokaryotes:
DNA is free floating in the cytoplasm, it is present as one long coiled-up strand (circular) without any histone proteins.
T / F:
Bacteria contain RNA.
False, they contain DNA.
T / F:
Viruses replicate through binary fission.
False, prokaryotes replicate through binary fission - and viruses are acellular.
T / F:
Bacteria have attached histone proteins.
False, unlike eukaryotes they have no histones attached.
What are plasmids?
Small loops of DNA that aren’t part of the circular DNA molecule, they contain genes for specific things such as antibiotic resistance.
T / F:
Plasmids can travel between prokaryotic cells.
True, this means some cells can have none but others may have several.
Name the main features of a prokaryotic cell:
- Cytoplasm
- Flagellum
- Circular DNA
- Plasmids
- Plasma membrane
- Cell wall
- Capsule
- (small) Ribosomes
What is the flagellum?
A long, hair-like structure that rotates to produce movement.
T / F:
Bacteria contain a plasma membrane.
True, prokaryotic and eukaryotic cells both contain a plasma membrane.
T / F:
Viruses move through rotation of their flagellum.
False, viruses do not have a flagellum.
T / F:
Some cells contain no flagella and some contain many flagella.
True.
What is the plasma membrane of a prokaryotic cell made from?
Mainly lipids and protiens.
T / F:
The cell wall of the prokaryote is made out of a protein coat called a capsid.
False, it is made of a polymer called murein,(capsid is on a virus).
What is murein?
A glycoprotein polymer which forms the cell wall in prokaryotes.
What is the capsule made up of?
Secreted slime.
T / F:
The cell wall of the prokaryote is made out of murein.
True.
What is the function of the cell wall of the prokaryote?
Supports the cell and prevents it from changing shape.
T / F:
The cell wall of the prokaryote is made out of phospholipids and proteins.
False, it is made of a polymer called murein.
Some prokaryotes contain a capsule, do bacteria contain a capsule?
Yes.
T / F:
The cell wall of the prokaryote is made out of cellulose.
False, it is made of a polymer called murein.
What is the function of the capsule?
They help protect the cell from attack by immune cells.
T / F:
The polymer murein (which is the main component in the prokaryotic cell wall) is a glycolipid.
False - it is a glycoprotein.
What is the function of the plasma membrane?
To control the movement of substances in and out of the cell.
T / F:
The polymer murein (which is the main component in the prokaryotic cell wall) is a glycoprotein.
True - it is a protein with a carbohydrate attached.
How do viruses replicate?
They use attachment proteins to bind to complementary receptor proteins on host cells. They inject their genetic material into the host cell and then replicates the virus using the host cells organelles.
Describe the steps involved in binary fission:
1) Circular DNA and Plasmids replicate (main loop replicated once, plasmids replicated many times).
2) Cell expands and DNA loops move to opposite poles.
3) The cytoplasm divides (cytokinesis)
4) Two daughter cells are produces, each with one circular DNA copy and a variable number of plasmids.
Why can some viruses only affect a single type of cell?
Because the attachment proteins must be complementary to the receptor proteins on the surface of host cells.
Using your knowledge of binary fission, explain why genes for traits such as antibiotic resistance are spread quickly.
Genes for traits such as this are held in plasmids rather than circular DNA, during binary fission the plasmids replicate many times rather than just once. This causes many more plasmids with this gene and they can be transferred between prokaryotic cells.
Why has it been said that viruses a ‘hijackers’ when replicating?
They inject their genetic material into the cell and then use the host cells own organelles to work for them.
