2.1.1g Prokaryotic Cells Flashcards
see showbie slide for diagram of prokaryotic & eukaryotic
Prokaryotic cells
- DO NOT have a nucleus
- DO NOT have membrane-bound organelles
- includes all bacterial cells
Eukaryotic cells
- DO have a nucleus
- DO have membrane-bound organelles
- includes all animal & plant cells
What is a prokaryote
a single celled organism without a nucleus & do not have membrane-bound organelles (eg. bacteria)
What is a eukaryote
have membranes around their many complex organelles.
these often have a specific function (eg. muscle fibres) & are part of multicellular organism
Prokaryotic cells may also contain…
extra small rings of DNA called PLASMIDS.
- plasmids code for very specific features sa. antibiotic resistance
- plasmids can be shared between bacteria to pass on resistance & also resistance can be passed on through binary fission
see showbie for diagram of bacterial cell (prokaryotic)
Structures that are ALWAYS PRESENT in Prokaryotic cells
- plasma membrane
- circular DNA sometimes referred to as a chromosome
- cytoplasm
- ribosomes
- cell wall made of cross-linked peptidoglycan
Additional structures SOMETIMES present in Prokaryotic cells
- pili
- plasmid
- capsule
- mesosome
- flagellum
Additional prokaryotic structures: pili
for attachment to other cells or surfaces, involved in sexual reproduction
Additional prokaryotic structures: plasmid
small circular piece of DNA, several may be present
Additional prokaryotic structures: capsule
Protective slimy layer which helps the cell to retain moisture & adhere to surfaces. Provides additional protection
Additional prokaryotic structures: mesosome
infolding of inner plasma membrane which contains enzymes required for respiration, associated w DNA during cell division, and helps w formation of new cell walls
Significance of infolding of plasma membrane
infolding of plasma membrane may form a photosynthetic membrane, or carry out nitrogen fixation
Additional prokaryotic structures: flagellum
a tail like structure which rotates to move the cell.
For locomotion, very simple structure
Structure of prokaryotic (always present): cell wall
rigid outer covering made of peptidoglycan
Features of prokaryotic cells (difference)
- extremely small cells (less than 2μm in diameter)
- no true nucleus
- DNA is circular (only one loop of DNA), not associated w proteins. Some DNA is in the form of plasmids
- very few organelles. No membrane bound organelles
- contains smaller 70S ribosomes (18nm)
- cell wall made of peptidoglycan (aka murein) - complex polymer formed from amino acids & sugars
- may have an outer slime capsule surrounding the cell
- flagella (when present) made of the protein flagellin, arranged in a helix
- divides by binary fission
eg: E. coli bacterium
Features of eukaryotic cells (differences)
- larger cells (10-100μm in dia)
- distinct nucleus is present
- DNA is linear (many chromosomes), is associated w proteins called histone. No plasmids
- many membrane bound organelles
- contains larger 80S ribosomes (22nm), involved in formation of more complex proteins
- plant cell wall made of cellulose. Fungi cell wall made of chitin
- no capsule surrounding the cell
- flagella (when present) made of microtubule proteins arranged in 9+2 arrangement
- divides by mitosis & meiosis
What is the theory of Endosymbiosis
That mitochondria & chloroplasts, & possibly other eukaryotic organelles, were formerly free-living bacteria, that is, prokaryotes.
The theory is that these prokaryotes were taken inside another cell as an endosymbiont (an organism that lives within the body or cells of another organism). This eventually led to the evolution of eukaryotic cells
see goodnotes for differences diagram between prokaryotes & eukaryotes
