Unit 1 Chapter 3 Flashcards
Chapter 3 (8 cards)
- Explain the theory of spontaneous generation why it is no longer accepted
Francesco Redi in 1668. He left some meat out in the open and covered other meat so flies could not get to it. Maggots only appeared on the uncovered meat, thus showing that maggots do not spontaneously generate.
life could arise from non-living matter
- Explain the distinguishing characteristics of prokaryotic cells
Nucleoid (not nucleus)
May have extra chromosomal DNA
Lack membrane enclosed organelles
Usually have cell wall to resist osmotic
shock
Bacteria – Ester linked phospholipid
Archaea- Ether linked phospholipid
Ribosomes are different than the eukaryotes (leverage)
May contain inclusions or storage
Some can enter / exit dormancy via sporulation and germination
- Describe common cell morphologies and cellular arrangements typical of prokaryotic cells and how cells maintain their morphology
Coccus - round
Bacillus - rod
Vibrio - curved rod
Coccobacillus - short rod
Spirillum - spiral
Spirochete - long, loose, helical spiral.
Morphology is maintained by the cell wall in most prokaryotic cells. The cell wall protects the cell from changes in osmotic pressure.
Isotonic solution. The solution is equal inside cell compared to outside of cell
Hypertonic Solution -more solution outside of the cell leading to decreased water in cell
Hypotonic - more solution inside the cell more water rushes in
- Describe internal and external structures of prokaryotic cells in terms of their physical structure, chemical structure, and function
Peptidoglycan is composed of polymers of alternating NAM and NAG subunits, which are cross-linked by peptide bridges linking NAM subunits from various glycan chains. This provides the cell wall with tensile strength in two dimensions.
Gm+: pentapeptide and tetrapeptide crosslinks
Gm-: only tetrapeptide crosslinks
- Describe internal and external structures of prokaryotic cells in terms of their physical structure, chemical structure, and function
Bacteria contain two common cell wall structural types. Gram-positive cell walls are structurally simple, containing a thick layer of peptidoglycan with embedded teichoic acid external to the plasma membrane.[20] Gram-negative cell walls are structurally more complex, containing three layers: the inner membrane, a thin layer of peptidoglycan, and an outer membrane containing lipopolysaccharide
Some gram-positive bacteria, including members of the Mycobacteriaceae, produce waxy mycolic acids found exterior to their structurally-distinct peptidoglycan.
The acid-fast staining protocol detects the presence of cell walls that are rich in mycolic acid. Acid-fast cells are not destained by acid-alcohol when stained red by carbolfuschin
- Compare and contrast vegetative cells and bacterial spores
Bacterial cells are generally observed as vegetative cells, but some genera of bacteria have the ability to form endospores, structures that essentially protect the bacterial genome in a dormant state when environmental conditions are unfavorable.
Vegetative cells produce dormant structures called spores when the environment is unfavourable
- Correctly order the events of sporulation
- DNA replicates
- Membranes form around DNA
- Forespore forms additional membranes
- Protective cortex forms around the spore
- Protein coat forms around the cortex
- Spore is released
- Describe the structure and function of pili, fimbriae and flagella
Some prokaryotic cells have fimbriae or pili, filamentous appendages that aid in attachment to surfaces. Pili are also used in the transfer of genetic material between cells
Some prokaryotic cells use one or more flagella to move through water. Peritrichous bacteria, which have numerous flagella, use runs and tumbles to move purposefully in the direction of a chemical attractant
Bacteria may produce two different types of protein appendages that aid in surface attachment (colonization).
Fimbriae typically are more numerous and shorter, used for attachment
Pili are longer and less numerous per cell.
Sex Pili be used to transfer genetic material between cells
