A2.2.5 - Prokaryote Cells Flashcards
Include these cell components: cell wall, plasma membrane, cytoplasm, naked DNA in a loop & 70S ribosomes. The type of prokaryotic cell structure required is that of Gram-positive eubacteria such as Bacillus & Staphylococcus. Students should appreciate that prokaryote cell structure varies. However, students are not required to know details of the variations such as the lack of cell walls in phytoplasmas and mycoplasmas. (9 cards)
A little thing to help remember what prokaryotic cells are
What does the prefix pro & suffix kary mean?
Pro: before
Kary: nucleus
No nucleus & most primitive type of cell
The prokaryote cell
What are some major characteristics of prokaryotes?
- Much smaller & simpler than ECs (many are less than 1µm in diameter)
- No nucleus
- Unicellular (no membrane-bound organelles)
Examples of PCs: bacteria & archaea
Typical cell components of Prokaryotes #1
What are the 3 main components of prokaryotes?
The 3 major characteristics of all cells
- Plasma membrane
→ Similar in composition to the membranes of eukaryotes
→ Plays a role in binary fission
→ Controls to a considerable extent the movement of materials in & out of the cell - Cytoplasm
→ Chemical reactions in the cytoplasm are not isolated from one another, ∴ reactions can be interfered. Still, prokaryotes have the most diverse metabolic reactions of all organisms - DNA: naked DNA in prokaryotes
→ 1 long, continuous thread of DNA; bacterial chromosome (in a region called nucleoid)
→ Not associated w/ histones
→ Involved w/ cell control & reproduction
Plasma membrane & cytoplasm are the same for both types of cells
Typical cell components of Prokaryotes #2
About 70S ribosomes in prokaryotes
- For protein synthesis
- Much smaller than eukaryotic ribosomes (70S < 80S)
→ Has lower mass as well - All prokaryotic ribosomes are free in the cytoplasm
- Usually ranges in diameter between 0.1~5.0µm
Ribosomes have 2 subunits
Typical cell components of Prokaryotes #3
2 additional typical components of prokaryotes
- Cell wall: Found outside of cell membrane
→ Composed of peptidoglycan (carbohydrate-protein complex)
→ Protects prokaryotes against toxins
→ Maintains shape of cell
→ Resists high osmotic pressures - Plasmid: Small circular pieces of DNA transferrable from one prokaryote to another [Horizontal gene transfer (HGT)]
→ Separate pieces from the chromosomal DNA
→ Can help the cell adapt to unusual circumstances
HGT ≠ VGT (vertical gene transfer) which occurs from reproduction
Gram-positive eubacteria
One major way of classifying bacteria
- Crystal Violet Dye
→ Gram-positive bacteria have cell walls that take on a violet/blue appearance in the presence of crsytal violet.
→ Examples of gram-positive bacteria are: bacillus & staphylococcus
Gram-negative bacteria do not react to crystal violet
Appreciation of the variation of prokaryote cell structures
What do some bacteria have an additional layer of?
- Some bacteria have an additional layer of a type of polysaccharide outside the cell wall called a capsule
→ Allows it to adhere to structures (i.e. teeth, skin, food)
Appreciation of the variation of prokaryote cell structures
What are pili & flagellum?
*Only in some bacterial cells
- Pili: hair-like growths on the outside of the cell wall
→ Allows attachment to other cells
→ Main function: Joining bacterial cells for the transfer of DNA from one cell to another (sexual reproduction) - Flagella: hair longer than pili
→ Main function: locomotion of the organism
→ Spins to propel the cell through its medium
Appreciation of the variation of prokaryote cell structures
What factors help distinguish distinct types of prokaryotes?
- Nutritional requirements
- Sources of energy
- Chemical composition
- Morphology (shape)
