Prokaryotic Cell and Virus Ultrastructure Flashcards
Prokaryotes general information - what are the 2 types? How do they store carbs etc
- Bacteria and Archaea
- Unicellular
- Simpler structure than Eukaryotic cells
- 100-1000x smaller than Eukaryotic cells
- 0.1-10 micrometers in length
- No nucleus/nuclear membrane or membrane-bound organelles
- Versatile, adaptable, very successful
- Store carbs as glycogen
What organelles do all prokaryotes contain?
- CSM, Cytoplasm, 70S Ribosomes, Loop of DNA, Peptidoglycan cell wall.
Which organelles do only some prokaryotes contain?
Infolding of the CSM, Flagella, Pili, Plasmids, Slime Capsules
How is bacterial DNA different to Eukaryotic DNA?
- Bacterial is circular (eukaryotic is linear) and occurs free in the cytoplasm
- Main function of bacterial DNA is possessing the genetic information for the replication of bacterial cells
Peptidoglycan cell wall function
- Physical barrier - polysaccharide chains cross-linked by peptide chains
- Excludes certain substances and protects cell from osmotic lysis and mechanical damage
What can infolding of the CSM allow bacteria to do?
- Photosynthesis
- Nitrogen fixation
Slime capsule function
- Sits outside the cell wall
- Help to protect bacteria from attack by other cells (eg cells of the immune system or other bacteria)
- Help bacteria to stick together for further protection
- Stop bacteria from drying out
Plasmids
Small loops of DNA found free in the cytoplasm and separate to the main DNA molecule:
- Can act as vectors in genetic engineering (or just naturally)
- Possess genes that can help them survive in adverse conditions (eg antibiotic resistance genes) and these can be passed onto other prokaryotes
Pili
- Gene transmission between bacteria cells
- Attachment to other cells/surfaces
- Involved in sexual reproduction
Virus general information
- Smaller than bacteria
- Parasitic and infectious
- Acellular and classified as non-living
- This is because they cannot respire/independently move/replicate/don’t have metabolic reactions/nutrition
- All have some sort of genetic material - DNA RNA or ssDNA - but this is very short usually
- Can only multiply inside a living host cell
- Infect all types of living organism
- No cell wall so antibiotics can’t destroy them
How do viruses replicate?
- Attachment proteins attach to receptors on the host cell
- Virus nucleic acid enters the host cell (nucleus)
- Viral nucleic acid is replicated in the host cell (reverse transcriptase makes DNA from RNA)
- Host cell codes for and produces viral proteins (capsids and enzymes)
- Host cell dies and new viruses are released
Capsid structure and function
- Protein coat that encloses and protects the genetic information
- If lipid envelope isn’t present then attachment proteins are on top of this
Lipid envelope structure and function
- These are phospholipids - formed from the membrane of the host cell they were made in
- Not present in all viruses
- If it’s there then a matrix forms between it and the capsids which forms links between the two
Reverse transcriptase function
- An enzyme that’s only present in a virus with RNA as the genetic material
- Converts RNA to DNA
Attachment proteins function
- Inject viral genetic material into eg host cells by binding to receptors on the host cell’s CSM
- Allow the virus to be identified
