1.2 Cell structure Flashcards
Prokaryotes
are organisms whose cells lack a nucleus (‘pro’ = before ; ‘karyon’ = nucleus)
Prokaryotes kingdom?
Monera
two distinct domains of prokaryotes
- Archaebacteria
- Eubacteria
Archaebacteria
found in extreme environments like high temperatures, salt concentrations or pH (i.e. extremophiles)
Eubacteria
traditional bacteria including most known pathogenic forms (e.g. E. coli, S. aureus, etc.)
Prokaryotic features
Cytoplasm Nucleoid Plasmids Ribosomes Cell membrane Cell wall Slime Capsule Flagella Pili
Cytoplasm
internal fluid component if the cell
Nucleoid
region of the cytoplasm where the DNA is located ( genophore is a circular DNA strand)
Plasmids
Autonomous circular DNA molecules that may be transferred between bacteria( horizontal gene transfer)
Ribosomes
complexes of RNA and protein that are responsible for polypeptide synthesis (prokaryote ribosome = 70S)
Polypeptide Synthesis
building blocks of proteins, involves transcription and translation
Cell membrane
Semi-permeable and selective barrier surrounding the cell
Cell Wall
rigid outer covering made of peptidoglycan; maintains shape and prevents bursting (lysis)
Slime Capsule
a thick polysaccharide layer used for protection against dessication (drying out) and phagocytosis
Flagella
Long slender projections containing a motor protein that enables movement (singular: flagellum)
Pili
Hair-like extensions that enable adherence to surfaces (attachment pili) or mediate bacterial conjugation (sex pili)
Binary Fission
is a form of asexual reproduction used by prokaryotic cells
Process of binary fission:
- The circular DNA is copied in response to a replication signal
- The two DNA loops attach to the membrane
- The membrane elongates and pinches off (cytokinesis), forming two cells
