2.2 - 2.3 prokaryotic cells & mitosis Flashcards
Gram positive bacteria is made of ..
-Thick layer peptidoglycan in their cell walls
-Teichoic acid trapped in thick layer
Gram negative bacteria is made of ..
-Thin layer peptidogylcan between 2 layers of membrane
-no teichoic acid
- outer membrane contains lypopolysaccharides
2 main types of bacteria can be distinguished by
Gram staining
How does gram staining work ?
- Add purple crystal violet / iodine complex all cells appear purple as they take in stain
- Add alcohol to decolorisation , only GN bacteria loose colour as layer of lipopolysaccharides is dissolved & can’t hold stakn
- Add red safranin counterstain to stain GN bacteria red. counterstain not seen on gram- positive bacteria because of the darker crystal violet stain.
Other than gram staining how else can bacteria be classified
Shape
Respiratory requirements
Respiratory requirements:
Obligate aerobes
Facultative aerobes
Obligate anaerobes
Need oxygen for respiration
Use oxygen if available but can manage without
Can only respire in absence of oxygen
How does the beta lactam (penicillin) antibiotic work
Why are they more affective against gram pos
It attacks gram positive bacteria by inhibiting the formation of cross links in the peptidoglycan layer of cell wall
- water moves into cell my osmosis , cell bursts
They have thick pep layer so the cell wall can be affected
How does the Glycopeptide antibiotic work
-They’re large polar molecules
- affective against gram positive
- difficult to penetrate outer membrane layer of gram neg
-
How does polypeptide antibiotics work?
- rarely used as can have serious side effects
- affective with - as they interact w phospholipids of outer membrane
What happens during the g1 interphase stage of mitosis?
Duplication of organelles like mitochondria
- cell growing in size and making of proteins
What happens in the s phase of interphase (mitosis)?
- chromosomes replicate becoming double stranded chromatids
What happens in the G2 phase of interphase (mitosis)?
Organelles and other materials needed for cell divisions are synthesised
When a cell starts to actively divide …
The chromosomes become shorter and denser allowing them to take up stains easier and be identified
When dna condenses (becomes shorter and denser ) how is it packaged efficiently ?
Dna winds around histones to produce nucleosomes
These intercatc o produce more coiling then they super coil
The cell cycle is controlled by …
Cyclins which attach to enzymes called cyclin dependent kinases
what takes place in the prophase phase of mitosis?
-dna condenses , chromsomes become visible
-nuclear membrane breaks down
-as centrioles divide and move to either pole spindle fibres form
what takes place in the metaphase phase of mitosis?
spindle fibres attach to centomeres
Chromosomes are lined up at cell equator by sf
what takes place in anaphase phase of mitosis?
centromeres separated , sc pulled apart, sister chromatids move to opp poles,
telpohase?
-nuclear envelopes form around 2 sets of chromosomes
-nucleoli reforms
- chromosomes decondense , lengthen can’t see
cytonkinesis?
2 identical daughter cells formed
what is assexual reproduction
reproduction involving one parent and produces genetically identical offspring
these methods of assexual reproduction rely on mitosis:
binary fission
producing spores
used by bacteria, splitting of one individual to form 2 new ones, causes exponential growth
fungi, plants, production of assexual spores that can grow into new individuals , spread over large distances
these methods of assexual reproduction rely on mitosis:
regeneration
producing buds
lizards, starfish, fungi – use of mitosis to regrow a body part that has been lost
yeast cells, hydra – an outgrowth from a parent organism which produces a smaller but genetically identical individual
these methods of assexual reproduction rely on mitosis:
vegatative propagation
parthogenesis
Producing identical plants from part of a plant
unfertilised egg cell develops into new indiviudal
