Prokaryotic cells Flashcards
What does a prokaryotic cell have?
-Pilli
-Flagella
-70s ribosomes
-Nuceloid
-Cell membrane
-Mesosomes
-Plasmids
-Cell wall
-Photosynthetic membranes
-Capsid/slime layer
What features do not all prokaryotic cells have?
-Flagella
-Plasmids
-Photosynthetic membranes
-Capsid/slime layer
What does pilli mean?
-Thread like protein projections found on the surface of some bacteria
-It is used to attach to the host cells for sexual reproduction
What is a nuceloid?
An area in a bacterium where we find a single length of coiled DNA
What are mesosomes?
-Either in foldings of the cell membrane in bacteria
-Could be human error when observing the cell
What is a photosynthetic membrane?
Produces glucose
What does the capsid do?
The protein coat of a bacteria which prevents the cell drying out and hides the fact that the cell is foreign
What are the features of prokaryotic cells?
-Smaller cells
-Always unicellular
-No nucleus, no membrane bound organelles
-Circular DNA
-Smaller ribosomes (70s)
-No cytoskelenton
-Cell wall containing peptoglycan
How do antibiotics affect bacteria cells?
-Some antibiotics target cell walls, some target 70s ribosomes
-Some inhibit the formation of the peptoglycan layer in the cell wall (this affects gram positive bacteria but doesn’t affect gram negative bacteria because their cell wall is hidden and less vital to their structure)
How do polypeptide antibiotics work?
They affect gram negative bacteria because it interacts with the phosopholipids on the outer membrane (this wouldn’t affect gram positive bacteria)
-Rarely used due to the severe side effects
How do most antibiotics work?
Target common processes e.g protein synthesis
What are viruses?
Intracellular parasites which can only exist and reproduce in the cells of other living organisms
-they all have similar shapes and structures but vary in genetic material
-viruses are classified depending on their type of genetic material and their mode of replication
-they are acellular (non-living)
What is a capsomer?
A repeating protein unit making up the capsid
What do viruses use their receptors and tails for?
To attach to host cells
What does the envelope do?
Prevents the body detecting that the virus is foreign
-not present in all viruses
What shapes can viruses be?
-Helical
-Polyhedral
-Spherical
-Complex
How can we classify viruses?
-Shape
-Size
-Genome
-Mode of replication
-Capsid structure
-Host organism
How does gram staining work?
-Gram positive bacteria goes blue/purple because it has a thicker layer of peptidoglycan
-Gram negative goes pink/red
What is a bacteriaphage?
A virus infecting bacteria
What are the stages of the lytic cycle?
- The T2 bacteriaphage attaches to a bacterium
- The phage DNA is injected into the host cell which causes the production of viral enzymes
- The phage DNA then inactivates the hosts DNA and takes over the cells biochemistry
- The phage DNA is replicated and the new phage particles form a protein coat around the phage DNA which produces the lysozyme enzyme
- The cell lyses (bursts)
What happens in the lysogenic cycle?
- T2 bacteriophage attatches to the bacterium
- Phage DNA is injected into the host cell which produces viral enzymes
- The viral DNA is incorporated into the host cells DNA
- The viral DNA is replicated each time the bacterium divides without harming the bacterium
- Remains dormant in the host cell until a trigger starts the lytic cycle
What are positive ssRNA viruses?
They are used directly as mRNA for translation into proteins at the ribosomes
What are negative ssRNA viruses?
-Must be transcribed into a sense strand first
-The virus imports RNA replicase which transcribes a sense strand
-This starts to act as mRNA which translates viral proteins and more RNA replicase allowing new viral particles to be produced
What is the retrovirus life cycle?
- The retrovirus attaches and attacks the animal cell
- The viral DNA enters the host cell and cannot be used as mRNA at this point
- The viral RNA is translated into viral DNA by reverse transcriptase in the cytoplasm
- This viral DNA is incorporated into the hosts DNA in the nucleus which directs the production of the new viral genome
- The RNA, mRNA and coat proteins are assembled and leave the cell by exocytosis
What are antiviral treatments?
-Target viral replication
-Target the receptors to stop viruses recognising the host cell
-Target enzymes which translate their viral DNA
-Inhibits protease enzymes which stops the budding of new virus particles
What are some examples of disease control?
-Nursing in isolation
-Preventing transmission from person to person
-Sterilising and disposing equipment
-Wearing protective clothing
What are some ethical implications of new medicines?
-Unethical to give drugs without human trials
-Difficult to decide to gets the drug
-Unclear side effects
